MJLorton Solar Power and Electronic Measurement Equipment Forum

Solar Power => Solar Power => Topic started by: birrbert on January 04, 2013, 06:29:18 AM

Title: First steps in using the Sun's energy
Post by: birrbert on January 04, 2013, 06:29:18 AM
Hello!

So, it's not much, but I finally managed to put my solar panels to work. I bought six panels (6 Volts x 100 mA = 0.6 Watts each). Dimensions: 12 cm x 4.5 cm x 0.5 cm. They look like the ones this guy uses in his video (https://www.youtube.com/watch?v=f1MMFkwdxHw). First photo attached (excuse the glare).

I wired them in series two by two, this way I got three 12 Volt/100 mA panels. Then I wired these three in parallel to get 12 Volts/300 mA. Second photo attached.

It's winter now and it was overcast all day, but without a load I measured 9-10 Volts coming out of my creation. Now, as I put a load on it, the voltage drops dramatically:
- attached a 12 Volt/200 mA fan and it goes down to ~1.7 Volts, the fan starts spinning only if I spin it first;
- attached a green LED and it goes down to ~2 Volts, the LED lights up;
- attached a green LED and it goes down to ~3 Volts, the LED lights up.

As noob this might sound, please try to explain to me what's the case here: is something wrong with my panels or just there isn't enough sunlight? :)

Thanks!

PS: my goal is to build some kind of charger with these panels, but I don't know yet what for.
Title: Re: First steps in using the Sun's energy
Post by: SeanB on January 04, 2013, 07:29:54 AM
You are in Romania, roughly 45 degrees north. Thus the sun at noon is roughly at 45 degrees from the vertical. Solar panel ratings are quoted at a standard illumination, roughly 2kW per square meter of panel, or basically high noon at the equator give or take. At your latitude the sun is roughly half that in summer, and being winter it will be even less, probably half again. Thus the panels will give at noon when held normal to the sun ( facing the sun at no angle at all, so they get all the sun) around 25% of the rated output. Thus you will get around 3V per panel but the maximum current will be around 25mA per panel, depending on the load. You will be able to charge a small flat lithium cell with each panel at current, but will need some form of charge controller for a small panel to regulate the power into the cell.
Title: Re: First steps in using the Sun's energy
Post by: birrbert on January 04, 2013, 08:44:19 AM
Thanks for the info SeanB!

So, when talking about a solar panel or cell there's a huge difference in performance between two states: loaded and not loaded. Why is that?

With the current wiring (three double cells in parallel), I can get a maximum loaded performance of 6 Volts x 75mA = 0.45 Watts, is that correct? If yes, that would be enough to slowly charge cell phones that have a 3.7 Volt rechargeable battery.

Could you please recommend a charge controller? Are there any for such a small panel/power? Could I make one myself? I see a nice little project developing here (interesting for me at least). :)

edit: I recovered a 5 Volt regulator (LM340T-5) from an old satellite receiver so I could use that, but probably 5 Volts is too much for a 3.7 Volt Li-Ion cell phone battery and it will damage it; maybe damage the phone too; please correct me if I'm wrong.
Title: Re: First steps in using the Sun's energy
Post by: kibi on January 04, 2013, 09:58:30 AM
I would recommend watching this video. Shahriar explains and demonstrates the experiment very well. The video is an hour long,  but very interesting. Watching this video should answer a lot of your questions.

http://www.youtube.com/watch?v=lrELRVFEx_s (http://www.youtube.com/watch?v=lrELRVFEx_s)
Title: Re: First steps in using the Sun's energy
Post by: birrbert on January 04, 2013, 12:48:11 PM
Thank you kibi for the link!

I watched the whole presentation and I liked it. It answered a few of my questions, plus gave me many new pieces of information, but that particular IC device is out of my reach... it's either sold in large quantities or shipping to Romania would cost a fortune; plus I'd love to try out a the demo board but that costs a fortune too, I mean way too much for a beginner hobbyist like me. Rhetorical: when will stuff like this be available for people like me?

Regarding solar panels: what I still don't understand is where does that big difference come from when they don't have a load and when they do have a load? Is the voltage dropping because my loads (fan and LED) are pulling all the current and current is low because of light conditions? How can I determine/measure the true capacity of my solar panels? Without knowing this information I can't really do anything, can I?

Regarding my idea of a solar charger: how about using a step-up converter? I found quite a few types on eBay at an affordable price. I could experiment with one that has a wider input, let's say 1-5 Volts and a 5 Volt fixed output (with a potentiometer I could set the right voltage to charge a specific battery). What do you think?

I know I ask a lot of questions, but please bear with me. I set out achievable goals for myself, but without explanation from more experienced people I can't progress. For example if I purchase something from eBay, it will take 4-6 weeks until it arrives to me and if I get the wrong item I will have to wait another 4-6 weeks for the next one to arrive.
Title: Re: First steps in using the Sun's energy
Post by: SeanB on January 04, 2013, 01:26:28 PM
A solar panel can be thought of as a voltage source with a series internal resistor. The voltage is essentially constant when exposed to light ( not really true but when lit by outdoor light it is pretty much true) but the resistor value is dependant on the amount of light on the front of the panel. Thus open circuit the panel will deliver 6V over a pretty big light range, from morning dawn to noon. The current available though depends on the light on the cell. If you short the cell with a ammeter you get the short circuit current ( 100mA max in your case) which is proportional to the light incident on the panel. Thus the current you can draw is somewhere between zero and the full amount. You choose the load to fall somewhere in that line. If you want to charge a simple cellphone cell with a built in charge controller then all you need is the simple 5V LDO you have to limit the voltage presented to the cell when it disconnects when fully charged. A simple shottky diode between the panel and the diode works for most cases, if you have some working cellphone battery units they can be connected across the panel to charge them slowly, probably will take a single panel 3 days to fully charge a battery by you.
Title: Re: First steps in using the Sun's energy
Post by: birrbert on January 06, 2013, 06:07:29 AM
Today is Sunday and my last free day. Tomorrow it's back to work so I decided to do something new and exciting on my last holiday. So I made a short video clip while playing with solar panels and a DC fan. For me it was a groundbreaking activity; I enjoyed it a lot. :)

The sun shone, no clouds close-by so I decided to hook up the solar panels I have in my window to a DC fan and play around a bit. As you will see at first I had to give the fan a little spin, but by noon the sun was high enough and strong enough to power the fan without me having to intervene. Also, at noon the fan was able to draw 100 mA at around 10-11 Volts from my little solar array.

Moreover, I gave a chance for the 5 Volt voltage regulator and it worked nicely. It's not burned or damaged, at least I know that now. :)

Please excuse the camerawork. My Canon SD1000 can film at a maximum resolution of 640x480 and the quality dropped a little more after uploading it to YouTube.

Link to video: https://www.youtube.com/watch?v=560G6E2G1NQ
Link to photo album: http://www.flickr.com/photos/birrbert/sets/72157632451440224/

It was a good little exercise - for me as a beginner - to learn about solar panels, wiring in series and parallel, setting up a multimeter to take volt and current measurements, implementing a voltage regulator in the circuit and finally very basic stuff like the use of crocodile clips. For the next step I ordered some analog volt and milliamp meters because with just one multimeter I can't keep an eye on all the factors in the same time. I will test a DC to DC step-up converter in low light/low voltage conditions.

In the long run my goal is to make a simple, relatively small size, yet precise and safe cell phone charger which is able to charge both on sunny and cloudy days.
Secondary goal: to learn and have fun along the way (and maybe to inspire beginners to start experimenting, just like Martin inspired me).
Title: Re: First steps in using the Sun's energy
Post by: MJLorton on January 09, 2013, 05:56:28 AM
I would recommend watching this video. Shahriar explains and demonstrates the experiment very well. The video is an hour long,  but very interesting. Watching this video should answer a lot of your questions.

http://www.youtube.com/watch?v=lrELRVFEx_s (http://www.youtube.com/watch?v=lrELRVFEx_s)

Another viewer also brought this one to my attention.
This is an excellent video...of great value to me...I have shared it on G+, FB, etc....
Title: Re: First steps in using the Sun's energy
Post by: MJLorton on January 09, 2013, 06:07:49 AM
Hats off to you Birrbert! What you are doing will certainly help others and it's a fun way to learn. I look forward to following your experiments.

Cheers, Martin.
Title: Re: First steps in using the Sun's energy
Post by: birrbert on January 09, 2013, 04:41:34 PM
I appreciate your support! Thank you!

The irony of fate: I'm stuck right now because the Sun's up a very short period of the day during which I'm in the office working. :-\
Title: Re: First steps in using the Sun's energy
Post by: birrbert on January 15, 2013, 03:52:41 PM
While I wait for the components to arrive I thought I'll raise a few questions or issues.

My plan is to build the charger using the components below in the following order:
- 12 Volts x 0.3 Amps = 3.6 Watt solar panels;
- one LM340T-5 voltage regulator (http://www.digchip.com/datasheets/download_datasheet.php?id=513599&part-number=LM340T5);
- one DC-DC Converter Step Up Module (0.9-5V to 5V 600mA) (http://www.ebay.com/itm/1pcs-DC-DC-Converter-Step-Up-Module-0-9-5V-to-5V-600mA-USB-Charger-/400361256193?pt=LH_DefaultDomain_0&hash=item5d3763f501) with USB port.

The solar panels would provide 12 Volts in full sunlight to the voltage regulator -> the voltage regulator would be connected to the solar panels to feed only 5 Volts maximum into the step-up module; in other words it would act as a safety device to protect the step-up module from receiving too much voltage  -> with a USB cable the cell phone would be connected directly to the step-up module and hopefully accept a charge.

I have two things in my head right now:

1) SeanB mentioned this already and I also read it somewhere that cell phones have some kind of built-in charge regulating circuit so 5 Volts would be OK and I shouldn't be able to damage the phone or the battery because this circuit will 'adapt' the 5 Volts according to its needs. This is great if it's true because the battery is 3.7 Volts only. So is this really true? Let me tell you why I'm asking. I'm still a bit confused because I have two cell phones which have two different chargers. One is a Nokia 1112 and it came with a charger that puts out 3.7 Volts/355 mA. The second is a Nokia X1-01 which came with a charger that puts out 5 Volts/350 mA. Both have 3.7 Volt Lithium-Ion batteries, they only differ in capacity. So what gives? Why does the Nokia 1112 charger put out only 3.7 Volts? How can you charge a 3.7 Volt battery with only 3.7 Volts? Or the two phones have different built-in charge controllers?

2) What would happen if in low light conditions the voltage regulator received less than 7.5 Volts from the solar panels? I'm asking this because I read in the LM340T-5 datasheet that 7.5 Volts is the minimum input to put out 5 Volts. I'm guessing that the LM340T-5 would gradually put out less than 5 Volts, but the step-up converter wouldn't mind because it can work with input voltages as low as 0.9 Volts. The only thing is that there will be current fluctuations. This is only theoretical, but could the fluctuating current damage the cell phone or its battery?

It's a very simple concept using just a few components, but unless I burn myself (i.e. blow up a Li-Ion battery) I believe I can learn a lot. :)
Title: Re: First steps in using the Sun's energy
Post by: MJLorton on January 16, 2013, 03:31:01 PM
I won't add much value to the current thread....but I came across this site with some really handy info related to electronics, solar, multimeters, etc: http://www.robotroom.com/

Reading this regarding small solar projects may be helpful: http://www.robotroom.com/Solar-Recharging.html
Title: Re: First steps in using the Sun's energy
Post by: birrbert on January 17, 2013, 02:46:59 AM
Great website. It feels good to read because it confirms some of my findings and concerns. Please keep them coming! :)
Title: Re: First steps in using the Sun's energy
Post by: birrbert on March 03, 2013, 06:54:12 AM
Hello! Long time no see. :)

This little project of mine was idle for a while, because I had to wait about 4 weeks for the step-up converters (1 (http://www.ebay.com/itm/1pcs-DC-DC-Converter-Step-Up-Module-0-9-5V-to-5V-600mA-USB-Charger-/400361256193?pt=LH_DefaultDomain_0&hash=item5d3763f501) | 2 (http://www.ebay.com/itm/1PCS-DC-DC-Converter-Step-Up-Boost-Module-1-5V-to-5V-500mA-USB-Charger-for-MP3-M-/251169704387?pt=LH_DefaultDomain_0&hash=item3a7ae189c3)) to arrive and then I needed a free day with sunshine to experiment. Luckily, today everything came together. Please allow me to summarize my findings.

Test subjects: Nokia 1112 (http://www.gsmarena.com/nokia_1112-1523.php), Nokia X1-01 (http://www.gsmarena.com/nokia_x1_01-3962.php), Samsung GT-E2120 (http://www.gsmarena.com/samsung_e2120-2900.php) and Apple iPhone 3GS (http://www.gsmarena.com/apple_iphone_3gs-2826.php).

Main components used: 12V/300mA solar array, LM340T-5 voltage regulator, cable with female USB sockets (http://files.cablewholesale.com/hires/31u1-02408.jpg) and another cable (http://www.ebay.com/itm/USB-Charger-Cable-Nokia-N97-N85-N86-6300-6120C-E51-E63-/290567683414?pt=AU_MobilePhoneAccessories&hash=item43a72efd56) with a male USB plug on the input side and 10 different plugs on the output side for various mobile phones.

Prior to this solar charge test I tried to charge all four mobile phones with the USB cable from eBay plugged into my laptop's USB port (which we know that supplies stable 5 Volts and 500 mA). All of them were charging fine except for the Nokia 1112; I'm guessing that 5 Volts was too high for him. Also, all tests were conducted with bright sunlight reaching the solar cells.

Results without step-up converters (only voltage regulator with 4.99 Volts stable output)
- Nokia 1112: didn't accept a charge at all; I couldn't make it to charge in any configuration so I won't talk about it anymore in the following paragraphs.
- Nokia X1-01: accepted a charge, but voltage was oscillating; it was dropping every second to 3.6 Volts which was too low for the phone and stopped the charging process; then it came back to 4.99 Volts for another second, started to charge, but it dropped to 3.6 Volts again and the process was in a loop.
- Samsung GT-E2120: accepted a charge and it was steadily charging at around 3.9-4 Volts.
- Apple iPhone 3GS: at first it accepted a charge and it was steadily charging at around 4.5 Volts, then I unplugged it to try another phone and when I plugged it back in it wouldn't accept a charge; it was weird, but I tried it a third time too and after plugging it in I got the message that 'Charging is not supported with this accessory'. I gave it a try with the original USB cable which came with the phone, but no luck there either. A bit later I plugged it again and it was accepting a charge.

Results with step-up converters
I kept the voltage regulator in the circuit to keep the step-up converters safe. The converter with the blue PCB (made by LC Technologies (http://www.lctech-inc.com/)) put out 4.93 Volts open circuit, the converter with the green PCB (no manufacturer) put out 5.35 Volts.

Basically I got the same results as without the step-up converters with a slight difference in the case of the Apple iPhone 3GS:
- Nokia X1-01: oscillating charge, 4.93 Volts dropping to 3.53 Volts with the blue converter and 5.35 Volts dropping to 3.55 Volts with the green converter.
- Samsung GT-E2120: steadily charging at around 3.88 Volts with the blue converter and 3.85 Volts with the green converter.
- Apple iPhone 3GS: didn't accept a charge with the blue converter at 4.36 Volts and accepted a steady charge at 4.80-5.08 Volts with the green converter (4.56 with the screen on).

Conclusions based on individual mobile phones:
- Nokia 1112: needs more research to find out how much voltage it needs to accept a charge; this value is most likely around the 3.7 Volt mark since the original Nokia charger puts out that much.
- Nokia X1-01: needs more research to find out why the voltage keeps dropping and what can be done to avoid this.
- Samsung GT-E2120: very easy to charge since it's accepting a relatively wide range of input voltages.
- Apple iPhone 3GS: relatively easy to charge, but with my current configuration and current sunlight conditions it was on the edge between accepting a charge or not accepting a charge.

Conclusions valid to all mobile phones:
- I had the feeling that with good sunlight charging was worse with the step-up converters compared to using just the regulator. The main reason I wanted a step-up converter was to be able to charge mobile phones in low light conditions too, but in low light conditions this configuration wouldn't work because this particular regulator would supply too low voltage to the converters. In that case these converters would work if instead of a voltage regulator I used a component that regulates only above 5 Volts; under 5 Volts this component should turn off and allow all the voltage and current to pass through and reach the converter freely. Questions is: which electronic component can do this? :)
- There are huge differences in voltage across different components of the circuit when under load and open circuit and this confuses me the most. I'm aware of the fact that the under load voltages count only; somehow these should be stabilized because charging any mobile phone can be achieved only with stable DC.

To-do list:
- Determining the minimum voltage at which mobile phones still accept a charge.
- It would be great to somehow determine the amount of current that my solar charger can put out while charging different mobile phones, because in this case I only measured the voltages. That way I could learn about the relationship between volts and amps.
- The input voltage of the step-up converters (received from the 5V regulator) was varying greatly. I guess that the converters act as a load too (to a certain degree) and the regulator can't put out a stable 5 Volts as it does without the converters in the circuit. It would be nice to log for a while and calculate min, max and average.

Also, I would appreciate any feedback from you guys who are more experienced to improve this little solar mobile phone charger. I would like to keep it as simple as possible, but at this stage it clearly needs some improvement. Just a side note here: I made a few test with a capacitor (4700uF/50V) and the Nokia X1-01 to check if the oscillation stops, but it didn't help; in some cases the voltage even dropped with the capacitor in the circuit. Maybe a super or hybrid capacitor would do a better job and then my to-do list would be irrelevant because there would probably be no need to have regulators and step-up converters in the circuit. :)
Title: Re: First steps in using the Sun's energy
Post by: SeanB on March 03, 2013, 07:21:32 AM
You probably will need to have some appreciable capacitance in parallel with the solar panel as well, 6700uF or more, rated at about 16V will do, and this will stop the oscillation, which is most likely the phone charger attempting to draw too much current from the converter. The convertrs do need a supply capable of supplying large current pulses, which the solar panel is not capable of doing, you need the big capacitor to do so. As well you need to use a connecting cable with low drop, so a minimum of 1.5mm cable for a small panel capable of 2A is not uncommon. I have used 4mm cable to connect mine, as it is on the roof and is connected by 40m of cable.
Title: Re: First steps in using the Sun's energy
Post by: birrbert on March 03, 2013, 10:51:44 AM
Hi SeanB!

I did a search for capacitors and found various types. For instance there are two types of 16V/10000uF electrolytic capacitors advertised based on 'working temp': 85 degrees Celsius (0.81 USD) and 105 degrees Celsius (0.96 USD). Also there's a third type called 'low impedance' (15 mOhm): this one costs 3.59 USD for one piece of 16V/8200uF.

And of course there are super capacitors that I could afford: 22F/2.5V/5.5A regular barrel shaped (http://i.imgur.com/CWHNvY0.jpg) which costs 2.84 USD and 10F/2.5V/3.8A flat shaped (http://i.imgur.com/VM5mswY.jpg) which made me think whether it's nicer to mount in a charger and costs 9.43 USD.

So, which one should I go for? And I have to mount this "in parallel with the solar panel" which is before the regulator. Is this correct?

edit:
In the same time I'm searching for a good LDO and I think I found one. Would you please comment it or recommend a better one?
MCP1703A-5002E/DB (http://www.tme.eu/ro/Document/d1a945b0361902c0e28584507cb22c28/mcp1703a.pdf) (output 5 V, max input 16 V, max output current 250 mA, SOT223-3 case) or MCP1703AT-5002E/MB (everything the same just SOT89-3 case).
To be honest I don't know the practical difference between the two cases. :)

edit2:
Another question that just popped into my mind is, what happened if I connected my solar cells to put out 600 mA at 6 Volts instead of the 300 mA at 12 Volts? That way I probably wouldn't have to worry that much about over-voltage and anyway it seems that my primary problem is low current rather than low voltage. I will probably try this configuration out too, but first I would like to achieve result with current one.
Title: Re: First steps in using the Sun's energy
Post by: SeanB on March 03, 2013, 12:57:01 PM
In this application either of the cheap ones will definitely work fine. In the interim look in some old computer motherboards for high value capacitors ( non bulged ones) and unsolder them and try them out in the interim.The supercaps will work as well, but you will have to stack a few in series so that the total voltage of the stack is higher than the open circuit voltage of the solar panel, which would mean you have placed a rechargeable battery across the panel output.

As to the LDO regulators, they both will work, but you will have a hard time soldering on to the packages, and they will need a heatsink. Look for a premade board with them on, or one in a TO220 package which will make it easier to connect in circuit.
Title: Re: First steps in using the Sun's energy
Post by: birrbert on September 08, 2013, 03:18:44 PM
So, I started hunting components again for this project and I found some interesting ones. For instance:
- This Li-Ion Battery Charging Board (http://www.ebay.com/itm/TP4056-1A-Current-Lithium-Battery-Charging-Board-DIY-Mobile-Power-Charging-/270958278638?pt=LH_DefaultDomain_0&hash=item3f165f37ee) which uses the TP4056 IC or;
- This very simple booster step-up module (http://www.ebay.com/itm/DC-DC-0-9V-5V-to-5V-600MA-USB-Step-Up-Module-Booster-Module-/370864835115?pt=LH_DefaultDomain_0&hash=item5659444a2b) with USB output. I couldn't identify the chip that it uses. I actually have two types, please see photos.

I made a drawing how I imagine the cell phone charger as of today. Please find it attached. It's based on the idea that it's much better to store the energy in a rechargeable battery and then - by boosting the voltage - use that as a source to charge the cell phone. What do you think? Would I need other components?
Title: Re: First steps in using the Sun's energy
Post by: SeanB on September 08, 2013, 04:30:07 PM
Will work, you will just need a switch to turn off the inverter to the phone when not in use so it does not kill the battery during non use.
Title: Re: First steps in using the Sun's energy
Post by: birrbert on September 09, 2013, 03:24:15 PM
Thank you very much Sean! You're a true gent! I can hardly wait for the parts to arrive and put it together! ::)

By the way, I bought a 300 mA analog current meter and I shorted the solar cells into it. With one cell it showed 100 mA and with three cells 300 mA. I was outside, the cells were exposed directly to the Sun and of course I aimed a bit. It's good to know that these cells produce what they claim. For instance, behind the window no matter how much I tried to aim, the cells could only produce half the current.
Title: Re: First steps in using the Sun's energy
Post by: MJLorton on September 16, 2013, 09:29:03 AM
Great stuff, look forward to seeing how it goes...have fun with it!

Cheers,
Martin.
Title: Re: First steps in using the Sun's energy
Post by: birrbert on October 01, 2013, 06:51:00 AM
Thanks! I'm certainly having fun. :)

I'm still waiting for the Li-Ion charge controller. In the meantime I charged the batteries with my "almost-ready-PSU". The disadvantage in my case is that the PSU doesn't have "real" current limiting. This is a special case of mine, but it might happen to others as well, especially with DIY power supplies.

- Let's say I set the Voltage to 4.2 Volts and apply no current limit, then I have the feeling that the battery pulls as much current as it can from the PSU. In one case it drew about 700 mA in the beginning and in time the value slowly decreased; in another case it pulled 1.2 A in the beginning and again with time the value slowly decreased. I disconnected the batteries when they were pulling only 50 mA.

- Now, if I limit the current (the goal would be to charge at a slower rate, e.g. 0.5C-0.8C) then the voltage output of the PSU drops too, meaning that I can't maintain the 4.2 Volt charging (to give the battery a full charge). I don't know if it matters for the Li-Ion battery if it's charged slower or quicker... I will have to experiment with this a bit more. By the way, the batteries I bought are small 1200 mA Li-Ion cells made for Nokia 8210/7210.

Questions and situations to experiment with:
- How much charge can I transfer from these cells into different types of mobile phones, using the cheap DC-DC step-up converter that I bought from eBay?
- Try to determine the efficiency of the step-up converter.
- Why doesn't the iPhone 3G S start charging if connected to the USB port of the step-up converter? Can the converter be modified?

Websites that I found helpful after browsing them for hours and hours:
- Battery University (http://batteryuniversity.com). I recommend checking out the article about charging lithium-ion batteries that provides a nice theoretical background in this topic.
- Brown Dog Gadgets (http://browndoggadgets.com). Especially interesting the Single USB Boost + Lithium Charge Controller Board that they sell.
- Adafruit Learning System (http://learn.adafruit.com). They have very nice documentation of the stuff they sell, easy to understand explanations, detailed discussion about challenges and possible obstacles that need to be taken into consideration when somebody makes this kind of charger.

edit:
A few minutes after writing this post I found this product on DX.com: Portable 5V "30000mAh" Li-ion Battery Solar Power Bank w/ Dual USB + LED - Black + Whitewhite-240475 (http://dx.com/p/portable-5v-15000mah-li-ion-battery-solar-power-bank-w-dual-usb-led-black-white-240475).
Well, if one engages in a project like I did, he needs to have a lot of motivation and a lot of fun to keep up and deliver some kind of result. I have to admit that seeing this product got me thinking. For one, the price is unbeatable (i.e. in my country the solar panel alone would cost more than the whole thing, not to mention the battery or other components); two, I started my project to learn about electronics by doing, but one might be able to learn the same way through buying a ready made product, examine it, disassemble it (if possible), etc. Maybe. Possibly. Just a few thoughts I wanted to throw in here.
Title: Re: First steps in using the Sun's energy
Post by: MJLorton on October 07, 2013, 02:59:30 PM
I think you'll learn far more doing exactly what you have been doing. Don't let that stop you from investigating a retail product but many of them don't deliver on what they say they will.
Title: Re: First steps in using the Sun's energy
Post by: birrbert on October 08, 2013, 04:21:37 AM
I agree with you! I will buy this charger sometimes and test it.

In the meantime I did a couple of things. I connected one Li-Ion cell to the boost converter and started charging a fully discharged Samsung cell phone. It didn't do much; the cell discharged quite fast (went down from ~4 Volts to ~2 Volts) and the phone showed only one bar of charge. Then I took three cells in parallel and used those to charge the phone furthermore. These ones discharged much slower (obviously) and the phone showed all five bars, though it didn't display the "battery full" message. Interesting thing that I didn't keep an eye on these three cells and by the time I "woke up" they went down to 0.8 Volts; still the phone was charging with a steady ~4.9 Volts which gives me the impression that this boost converter does a good job.

This was one step in determining the efficiency of the converter. Next, I have to check the Amps too (from the cells to the converter and from the converter to the phone separately), but it's damn hard without proper equipment. :)

And here's something I don't understand. When everything is connected and the cells are charging the phone through the converter, if I take a Voltage measurement with the multimeter at the cell terminals I see the Voltage (typically 3.7-4 Volts), but when I take the same measurements at the input terminals of the converter I usually see 1.9-2.1 Volts. What gives? I mean there's nothing between the cells and the input side of the converter, only the cable that connects them.

edit:
1. During usage the converter gets quite warm. I hope that it will do it's job later too when I put it in an enclosure.
2. Is there a way to add some kind of charge state indicator to my system? For example three LED's which turn on for 10 seconds at the push of a button: one LED would show that the battery bank is low, two LED's that it's halfway charged and three LED's that it's fully charged. The idea would be to keep power consumption minimal, hence the LED's and the push button. Do you guys have experience or an idea for this?

edit2:
Regarding the charge state indicator, I just remembered that the charge controller I have chosen has some LED's on it so maybe I can use those, but those light up only when charging is in progress.
Title: Re: First steps in using the Sun's energy
Post by: gording on October 11, 2013, 02:55:45 PM
Hello Birrbert

I'm glad that I found this forum and your thread. Now there's two of us! :) I live in Poland - Warsaw. By coicidence I've started exactly simillar project like you do. :)
Not knowing about you and this forum I've come to allmost exactly the same solution and project as you did.However im still on much earlier stage of construction. I've spend couple of weeks completing my solar panels. I've made them of single wafers wich I've solderd by myself, then I've bought a frame and encapsulated the wafers in a electrotechnical sylicone. The panel alltogether produces around 6V and 2Amps open circut. Theoretically. Why 2A? Well I live in a flat with windows on one side of the world only. And the side is north-east. :/ :( Putting panel on top of the roof is out of case as the community in my building would'nt allow for this. So I had to put it outside my window. By making it 2Amps i hoped i will secure myself against all the hours when my windows are shaded. Fev days ago measurments showed 6,5 Volts open circut and 1,1Amps at bright sunny day but with the sun around 50 degrees to the side of panel face. Didn't check it yet with shaded conditions. Only 3 days ago I've made a mounting frame and hung it outside the window. Now all i got is panel outside and bare cables inside :)
I've allready orderd both blue and green step-up converters. I do allso already have a nice LDO voltage regulator in 220 type body. I also ordered such a meter:

http://www.ebay.com/itm/181214038738?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649

I already know from Martin films that there are better meters but I think I should be quite satisfied with this one keeping in mind the good price of it.
Now next step will probably be to buy a 3,7V li-ion battery. Perhaps i will go into a 18650 type.
My Samsung galaxy s3 battery is 2100mA, 7,98Wh
So i will probably try to buy a few18650 batteries to make something around 5000mA of them so I could charge my and my wifes phone as well in one night.
I need to find out some more about the  charge controller which you bought. Would it prevent our li-ion external batteries from being overcharged?
Are there any other options to protect external battery from being drained by step up converter in no use time than a on/off switch. I'd like to make it as simple as possible and don't quite like the fact that one have to remember to switch toe switch off after disconnecting the phone - a thing easy to forget. Especially that probably it won't be just me using this charger.

Well I'm very glad we could exchange our experiences and learn together. Cause actually all the thin is about learning and having fun from it at the same time isn't it :)
If you'd like i can post some pictures of my panels outside my window later when i get back home from my work's trip I am on now.

edit: I looked at your scheme. Noticed there's no LDO voltage regulator between solar panel and charge controller. On the ebay auction also theres nothing about output of that charge charge controller. I think I could on a shiny day get over 6,5Volts under load conditions. Is that not to much to the 3,7V battery? Also if this charge controller doesn't lower the voltage then the 6,5v would go straight to our step up converter and then  directly to a phone.

edit2: I think I saw somewhere on our Polish websites a protection circuit which prevents 3,7 battery from being drained if we charge to many phones in poor light conditions ;) We could implement it between external battery and step up converter. 
Yep, actually it was here.
http://www.batimex.pl/towary.php?idzastosowania=1253&idzastosowanianad=1050&search=&selectLanguage=en&selectCurrency=2
Probably we could find something similar on ebay for a better price. However I will probably buy it from them as they are just a few kilometers from my home. I know they also have a Li-ion batteries with protection boards already installed in battery's casing so I will hesitate from buying a battery on ebay until I pay them a visit and talk to them.
Cheers
Konrad Hanc
Title: Re: First steps in using the Sun's energy
Post by: birrbert on October 13, 2013, 12:43:56 PM
Hi gording! Welcome to the forum! Please post photos with explanations about your progress!

To address a couple of your concerns:
- The charge controller I chose was made specifically for 3.7 Volt Lithium-Ion rechargeable batteries. It has overcharging protection, because it will stop when the batteries are at 4.2 Volts. Also, it uses 1/10 of the charge current as termination current.
- Here (http://lygte-info.dk/review/Review%20Charger%20TP4056%20UK.html) is a review of the charge controller using the TP4056 chip. The reviewer guy states that " When charger is disconnected from power, but with a battery in, it will draw below 1uA from the battery." While this is valid for the charge controller, I have no clue about the current consumption of the step-up converter, so it's a thing worth looking into sometimes.
- There's no need for an LDO regulator. The TP4056 can handle a maximum of 8 Volts input, so you should be fine because your solar cells will produce a maximum of 6.5 Volts. The output is a stable 4.2 Volts.
- Your concern about draining the battery too low is valid. I forgot to check on them once and they went down to 0.8 Volts, as I mentioned in my previous post, but I immediately charged them up and hoped they not got damaged. I bought two protection boards for testing: this one (http://www.ebay.com/itm/1-Protection-Circuit-Module-PCM-PCB-for-Cylinderical-18650-Li-ion-Battery-D-17mm-/221080001614?pt=LH_DefaultDomain_0&hash=item3379651c4e) and this one (http://www.ebay.com/itm/Single-cell-4A-Li-ion-Lithium-18650-14450-Battery-Input-Ouput-Protection-PCB-/121035944765?pt=US_Rechargeable_Batteries&hash=item1c2e4df33d). These are good for testing and learning, but otherwise it's best to buy the battery with built-in protection board, in my opinion.

Right now I'm waiting for info regarding the issues I raised previously. I'm especially interested in an explanation regarding the difference in Voltage at the battery terminals and the step-up converter. I also couldn't find info about the technical requirements for charging an iPhone 3G S through USB.

Regarding batteries, I found one locally for a good price: Swing 4400 (http://www.boston-power.com/products/swing-4400) from Boston Power. It would be great to test it, but don't have the funds for it yet (I just spent some money on silicone cables from Franky's shop)!
Title: Re: First steps in using the Sun's energy
Post by: gording on October 13, 2013, 04:44:48 PM
Hi Birrbert :)
Thanks for your reply.
I'm still waiting for some main components to arrive, like step up converter. But in the meantime managed to make a simple circuit. I connected solar panel output to a pcb board. As I have no battery yet, I placed an LDO voltage regulator. And on a very cloudy day I had with cell phone connected 5,5v from the panels. And only 4,7 coming into phone. I write "only" because I thought LDO will always give 5v on the output. However it did gave 5v on output on open circuit, under load conditions I only got 4,7. Around 0,8v drop. The phone didn't charge at all because all my "was-to-be-mighty" panel gave was 70mA on open circuit. Probably I would do better today if I connected solar panel straight to the phone, avoiding LDO. But I had no time to play with it for longer. Do you have any experience with LDO voltage regulators?  On a product card I've found that they require to mount two at least 22micro farads capacitors. One on source-negatve, and other on load-negative. I've mounted two 100 micro fahrads, however I have no idea if it has any influence on my circuit. The only I can think of is that it would support voltage for a few seconds when suddenly disconnecting solar panel. But I don't think that is the reason of mounting them on. BTW I had a little fire on my pcb last night when at the first time no knowing what I'm reallly doing I connected the capacitor other way round. Lesson learned!
Thanks for the TP4056 details. I will certainly familiarize myself with them.
Will post some photos in couple of days, when I'll find some spare time.
How about if you dismantle some old usb charger if you have one and connect it to the iPhone and use an multimeter on it? I had an old Samsung charger - the one you connect to the wall socket. I cut the phone plug out and mounted usb socket in there. I also have a Usb cable so by using it i managed to connect a phone and check that the wall charger gives constant 5,05v both open circuit and with load on/phone connected. I also checked the current a phone drains. Now I know that with empty battery it drains around 480mA which drops some much lower amperage when almost fully charged. (I don't remember the value now, but I have it written somewhere). If you do the same you will at least know what the original charger produce and could then compare it with what your solar panel gives and see if you can do anything to change the solar panel or the step up converter into what the original charger gives.
Bye :)
Title: Re: First steps in using the Sun's energy
Post by: birrbert on October 15, 2013, 06:12:43 AM
I found my answer about charging Apple gadgets through USB on Adafruit Learning System. It's well written, detailed and for the most part easy, so all I need now is some brain activity (i.e. wisdom) and testing to fully understand it. Great people these folks over at Adafruit!

Link: http://learn.adafruit.com/minty-boost/icharging

gording, you didn't specify what type of LDO you are working with, but please DO NOT AVOID IT! Don't connect the solar panel straight to the phone, because you will damage it! You have no control over the Voltage output of the solar panel, thus you have no way of knowing how much Voltage is going into the phone. I don't know if cell phones have any kind of over-voltage protection, but I know one thing for sure: they aren't as cheap as a capacitor that you popped the other day. :)

edit:
I just watched the video that Ladyada posted and I realized how important resistors are. They play a huge role in every electronic device or circuit. I have the impression that everything is circulating around resistors.

edit2:
Guys, is there anybody here who could help understand how the blue and green Chinese step-up converter work? I typed into Google what is written on the components, but couldn't find any usable piece of info.
The green one has an inductor labeled 220, a resistor labeled 222, three SMD capacitors, two diodes (one SMD and the other  labeled SS14) and one small-black-IC looking-chip labeled E5 00. The blue one uses mostly the same components, except for the inductor which is labeled 470, the resistor labeled 102, plus it has one less capacitor and instead of SMD the one capacitor is electrolytic.
Title: Re: First steps in using the Sun's energy
Post by: dr_p on October 15, 2013, 09:21:40 AM
SMD resistors are usually marked with 3 (or 4) digits. The first 2 (or 3) are straight up value, the last is multiplier (power of 10).
So:
 153 is 15*10^3=15*1000=15000=15k
 4701 is 470*10^1=470*10=4700=4k7

Other Rs are coded in a "nasty way", so you better read this (http://www.marsport.org.uk/smd/res.htm).

Inductors are marked the same way, but the value is in micro-Henry (uH).
So a 470 inductor is 47uH, a 331 is 330uH. I have also seen inductors marked 4R7 and I presume it means 4.7uH, as there is no way of marking it with the 3 digit code.

Now, regarding your boost converter: I've recently been interested in these. I bought THIS  (http://www.ebay.com/itm/3V-to-5V-1A-USB-Charger-DC-DC-Converter-Step-Up-Boost-Module-for-MP3-MP4-Phone-/390673638390?pt=LH_DefaultDomain_2&hash=item5af5f6a3f6)module and the IC was marked AL205. Other eBay pictures showed it as AL289. So I realized this is not the IC name, but a code. I finally suspected the IC used is a FP6291 (http://www.micro-bridge.com/data/Feeling-tech/FP6291.pdf), based on the pinout and specs (1MHz, 1A) etc. The datasheet also states, under "marking information", that the package is coded with ALxxx, so this is definitely it.
What I'm saying is that it can be difficult to find an IC from what is written on it. But in your case I don't think it's that important what IC it is.

You were asking how they work. They are classic "boost converters", you can google that.
I still have one of the FP6291 modules, so if you're interested you can have it, no charge.
Title: Re: First steps in using the Sun's energy
Post by: gording on October 17, 2013, 06:58:20 PM
Under the link below is my film with my attempt to charge my phone using 4 AA batteries and LDO regulator - failed. If you have any idea what am I doing wrong I will appreciate your suggestions. Sorry, I've tried for over one hour to post a youtube film directly in here instead of a link but failure again. None of "posting youtube video into a forum" worked for me.  :(

http://www.youtube.com/watch?v=Au4tL3gGnz4


Title: Re: First steps in using the Sun's energy
Post by: birrbert on October 18, 2013, 02:43:11 AM
You still didn't say the exact name of the LDO. Knowing that, would help me a lot in understanding.

Also, try connecting some other type of load instead of the phone, like a small fan that consumes less Amps than the phone, or a small 4-5 Volt light bulb or anything that accepts 5 Volts and consumes little power. Cell phones and especially smart phones usually need 500 mA more or less stable current, otherwise they won't even start charging.

I personally tried the LM340T-5 voltage regulator. Technically this is not an LDO, because it needs at least 7.5 Volts input for 5 Volts output, but it worked. I powered it from an adapter, it gave stable 5 Volts and enough Amps to charge the cell phone.

PS: nice assistant you got there. :)
Title: Re: First steps in using the Sun's energy
Post by: dr_p on October 18, 2013, 05:27:42 AM
Under the link below is my film with my attempt to charge my phone using 4 AA batteries and LDO regulator - failed. If you have any idea what am I doing wrong I will appreciate your suggestions. Sorry, I've tried for over one hour to post a youtube film directly in here instead of a link but failure again. None of "posting youtube video into a forum" worked for me.  :(

http://www.youtube.com/watch?v=Au4tL3gGnz4

The phone's eating the 7mA, so it's battery seems to be almost full.  Put some other load or discharge the battery and try again.
Title: Re: First steps in using the Sun's energy
Post by: gording on October 19, 2013, 10:43:44 AM
Hi

Sorry, silly me. At the beginning I thought that just saying it's a 5V LDO explains everything ;) Now I know it doesn't. Ok so it is LM 2940
http://electropark.pl/attachment.php?id_attachment=471 (http://electropark.pl/attachment.php?id_attachment=471)
By the way, does anyone know if those capacitors witch manufacturer suggest to install on that LDO are really necessary and what for? (Keeping in mind what do I use it for) I did installed them however they are a pain in the a...  Very tiny, difficult to solder on an LDO and already fallen of couple of times. I just can't solder them on properly. I have couple of this LDO's. When I connected one without capacitors I didn't realized any difference in the voltage nor in the amps.
The phone's battery I was trying to charge was almost discharged - showed only 10% charge so it is not the issue dr_p suggests.

I allso connected for a short period of time batteries directly to phone, without LDO. Voltage was around 5,5V and again only 20mA flowing. I did also connected other phone (with LDO again this time - didn't want to damage it) Same problem 7mA.
I'm waiting for some free time during the day to try to do the experiment again but instead of 4 AA batteries use my solar panel.
Other idea I've got is to repeat experiment but using this time 4 AA rechargeable batteries. 4*1,2V (1,3V) should give nice 5v, and no need for an LDO, and then see how many mA flows into the victim phone.
Maybe it was the batteries I used. Maybe they were the problem.
 Anyway when the charge controller arrives - the one which birrbert also ordered and 5v step up converter the LDO will become unnecessary.

 
Title: Re: First steps in using the Sun's energy
Post by: SeanB on October 19, 2013, 11:42:05 AM
The capacitors are needed, otherwise you will find there are input voltage and current combinations along with certain loads which make it a very good oscillator. This is because the control loops are invariably a lot faster in reaction than the very slow PNP lateral transistors used in the LDO to give a low dropout voltage. The capacitors slow the loop response time down so the control loop has low enough gain so as not to oscillate. You will find you typically need 100uF or more to make them unconditionally stable at all loads.
Title: Re: First steps in using the Sun's energy
Post by: gording on October 22, 2013, 09:31:11 AM
Thank you SeanB - now I understand :)

I've made a little progress and see what have I discovered:

http://www.youtube.com/watch?v=FSzpMTeBYu4


Also under here's the video with my other concern: Is it normal for an 5V LDO LM2940 to give 5v on the otput without load but only 4,3v under load conditions?

http://www.youtube.com/watch?v=kvomU_Y15Y4

If you'd like to see my solar panel that's how it looks like:

http://www.youtube.com/watch?v=HYmqLhKaJKA
Title: Re: First steps in using the Sun's energy
Post by: birrbert on October 22, 2013, 02:18:33 PM
Hey Konrad!

I have a same cheap, yellow multimeter like you and now that you started working with it, I noticed something: I think that for measuring milliAmp you have to put the red probe in the other red socket. So, Volts and Ohms and milliAmps use the same red socket and only the Amps are in the second red socket. Please check with a load that pulls 200 mA max and I'm pretty sure this will be the situation. I don't have the possibility to try it right not.

Regarding that alligator clip cable that you use, I have no idea what's going on. I also have those and they seem to be very low quality. I "disassembled" like three or four and put the alligator clips on new, thicker cable. Maybe I should do this to all of them to avoid future confusion, otherwise these damn small details make me go crazy. Yeah, beginner's mistake that the last place to search for the problem is the cable.

Regarding the LDO, I tried a similar one that you have, MCP1825S-5002EA. According to the datasheet it accepts 6 V input and can give 5 V output / 500 mA. Under no load conditions it does what is says, but under load it can output less, just like yours. This could be due to losses or resistance in the cables/connections/breadboard/etc. or we are missing some additional components or simply this is general behavior. In my case I don't remember the exact numbers, but I know that without load it was 5 V and with load it was 4.(something)...
Title: Re: First steps in using the Sun's energy
Post by: Mr Eastwood on October 22, 2013, 05:52:00 PM
Quote
I've made a little progress and see what have I discovered:


Hi,   I think it might be your multimeter;  I was looking for an circuit diagram of your meter and stumbled on this page which describes a meter similar to yours and they appear to not have a very good input impedence.  http://tubesound.com/2011/05/13/limitations-of-cheap-meters/ (http://tubesound.com/2011/05/13/limitations-of-cheap-meters/)  Could this be the reason for the weird readings?
Title: Re: First steps in using the Sun's energy
Post by: birrbert on October 23, 2013, 01:30:19 PM
Hi! I couldn't stand not to test a few things. Results below.

Multimeter and measuring mA
I wrote that I have the same multimeter as Konrad so this meant that I could do Amp measuring. I had a fan that consumes only 40 mA at 5 V. I connected it in series with the multimeter and started measuring current. The circuit was working only when I had the red probe in the 10 A (top red) socket, although it's clearly written on the multimeter that the Volts/Ohms/mA are measured using the red socket situated between the 10 A socket and the black one. Please see attached photo!
Anyway, I flicked the dial through all the mA ranges and there was no change like in Konrad's case, i.e. I saw 40 mA everywhere. Still, it's weird to see one thing shown on the multimeter and get a different result. The question is, why is this and why would they put the mA measurement together with the Volts and Ohms in the first place?

LDO, 6V/5V
I took my MCP1825S-5002EA in TO-220 package and took measurements. Input was 6 V and I used no additional components, just the LDO, cables and the fan mentioned in the previous paragraph.

- no load: 4.94 V.
- load: 4.93 V on the LDO side and 4.71 V on the fan side.

Again, this difference on the two sides of the cable occurs, just this time it's much smaller than in my post about the step-up converter (4 V vs. 2 V).
Title: Re: First steps in using the Sun's energy
Post by: tipidsolar on January 15, 2014, 07:14:32 PM
Hi Masters,

Sorry im just a newbie here even into these Solar power things. Im form Philippines , as you have heard we where hit by the Strongest Typhoon Landed on the planet. Up to now our Brgy.. in Ormoc City Leyte still doesn't have electricity So im planning to build a simple solar power system setup . My target is

1pc -100 Watt Solar panel 12v
1pc - 20 amp Charge Controller prepare to use the PWM budget wise because MPPT is expensive here.
1pc - 100AH Deep Cycle Battery
hope this setup can run 5 LED 4 watts and 2 Stand Fan 12v @ 15 Watts ( which im planning to use whole day? )
would this be possible ? as i am not familiar with the computation.

Please guide me doing my first Solar Setup

Thansk,
Title: Re: First steps in using the Sun's energy
Post by: SeanB on January 15, 2014, 11:44:10 PM
You might want to get a second panel to charge the battery and also have enough power to do things like charge a cellphone or two during the day or run a laptop. Currently the 100W panel will barely be able to charge the battery with the constant fan load, and will take over a week to fully charge the battery. Fine for an intermittent load but you want more than the single panel can do. Thus a second panel in parallel with the one and going through the same charger will work. The battery is capable of running the lights all night along with the fan provided you put the energy back the next day along with the losses.
Title: Re: First steps in using the Sun's energy
Post by: tipidsolar on January 16, 2014, 12:51:45 PM
@SeanB

So does it means that 100watts panel cannot fully charge the 100 AH battery ? does the 2 stand fan which is 12v DC 15 watts cannot be accommodated by the 100 watts panel? like how many hours it can run?

How may hours can a deep cycle 100 AH battery if being uses in 30 watts?

Sorry for being noob sir .

What if i only use the lights for 4 hours and let 2 lights run over night and 2 stand fan running over night?

Thanks in advance...
Title: Re: First steps in using the Sun's energy
Post by: SeanB on January 16, 2014, 01:14:30 PM
100W panel typically will charge the cell at around 4-5A, and usable time will be around 8 hours in a typical sunny day, giving you a charge return into the battery of  between 30-50 Ah back into the cell. You will need 2 days to fully charge the battery from flat with no draw, and typically it should have enough capacity to not go below 50% charge if there is no sun for a day or two. Fan draw is around 1.5A, and over 24 hours it will use about 40Ah of the battery capacity, and will basically take around a third of the charge current through the day. Lights will use about 20Ah if they are on from sunset to around sunrise ( assuming 2 are running all the time and 2 are off at around midnight) so your battery will slowly discharge each day until it goes flat. Just not enough energy coming in.

What you want to get is a good first start, but you will find that you need to use less power so that you do not damage the battery.  You will need to cut the load somewhat, so using a fan for a few hours and not all night, and having only one light on all night with the others being off around 10PM will keep the load low enough that the battery does not go flat, which will damage it capacity wise if done for only a few cycles. a second panel will enable the panel to charge the battery fully each day, and will give spare power to run eg the fans during the day as well.
Title: Re: First steps in using the Sun's energy
Post by: tipidsolar on January 16, 2014, 05:39:14 PM
Thanks for the Quick reply SeanB.. How about on day time can i still use my Fan running while charging?

a second panel will enable the panel to charge the battery fully each day, and will give spare power to run eg the fans during the day as well.

How about buying a MPPT charger than additional 100 watt panel? ived watts one of the video saying that because im using regular charge controller their are chances i will lost 40% from 100 watts?

Therefore your recommendation would be like this?

100 watt panel
1 charge controller
1 fan 12dc v 15 watts ( how many hours is the maximum?)
4 Led lights which only 2 off by 10 pm while 2 running over night?

or can you give me more detail specs for my setup..  :-[


Thanks
Title: Re: First steps in using the Sun's energy
Post by: gording on February 08, 2014, 01:57:34 PM
Hello:)
It's been couple of months since I wrote last in this topic. However my project has evolved and if you'd like to see how it looks right now please watch the wideo under the link below.
http://youtu.be/7kSss09-kjQ

Title: Re: First steps in using the Sun's energy
Post by: birrbert on February 09, 2014, 05:22:14 AM
Welcome back gording! :)

It's nice to see that you got something working, but I think you don't need two step-up converters. You should let the Li-Ion charger to charge the battery directly; I wouldn't put any step-up converter there. I would put the step-up converter only at the end of the circuit to step-up the the 3.7 Volts coming from the battery to 5 Volts. I would experiment with different types of step-up converters to figure out which one does a better job. I will actually do something like this since now I have a working power supply which I can use when there's no sunshine.

Also, I've been thinking a bit. I'm not sure, but experimenting with this type of solar charging might be useless in some regards. It might be OK for somebody if the goal is to learn, but otherwise it's useless, because others have done it before and have done it in a professional way, for example Adafruit (http://www.adafruit.com/category/67) or Brown Dog Gadgets (http://www.browndoggadgets.com/). I'm just a bit unsure what kind of new stuff can we add to the topic?

Doctor, I'm so uncertain lately! Or maybe not? ::)
Title: Re: First steps in using the Sun's energy
Post by: gording on February 09, 2014, 09:18:33 AM
Hello Birrbert

Well, actually it is done like you say. The Li-ion battery is charged directly by the charger unit. One step up converter (the selectable one) is used to increase voltage coming out from the battery to supply the meters, other is used to convert voltage , also coming out from the battery to charge the phone. Could I use there one converter, and supply 2 meters and charge mobile phone from this one converter only? Probably I could. Maybe I'll try to get rid of the green converter at the very end and instead use the selectable one with voltage on the output selected to 5V.  Adafruit gadgets are not cheap, and I prefer to learn by myself even if I discover something that was long ago already discovered ;)
Title: Re: First steps in using the Sun's energy
Post by: birrbert on February 09, 2014, 11:40:16 AM
Out of curiosity: can you calculate how much you spent until now?
Title: Re: First steps in using the Sun's energy
Post by: gording on February 10, 2014, 07:56:09 AM
If you calculate how much energy in terms of cost would I use by using factory charger and plugin it into wall socket, then probably for 100 years of using it I would pay less than the costs of building my solar charger.
 But first of all: This charger was NEVER meant to be financially viable project. For most it's hobby for spending free time, secondary it's learning platform.  My another project after this will probably be a laptop power supply. A flat where I live in limits me very seriously as of the size (power output) of solar arrays, cause all the windows face north-east direction.
Until I move to a new place I have to live with what I've got.  My energy harvest time is from sunrise until around 11 a.m. And that's it. With this conditions none solar project can be financially viable. However, keeping in mind it's mainly a hobby project I still do this. Now next step is to calculate how much window area would I have to use to supply laptop, and deciding if it is feasible. Most probably it's not. Still waiting for a socket meter to check exactly how much my laptop consumes.

Coming back to costs of current project. All the wiring, switches and converters were actually very cheap. The step up converters AFAIR were about 2-3 $ each, Li-ion charging module similarly. The greatest cost was the part that sits outside of the window. First solar panels I bought in Polish web site were very expensive. The next panels I found later on eBay were much much cheaper, however still the greatest cost was actually the silicone for encapsulating the panels. It cost me around 30$, for 1 litre bottle, out of which I used half - but it was the smallest bottle available. There aren't many electrotechnical  silicones on the market, so not much to choose from.

Probably if in future I'd decide to build a bigger project I'd go for factory made panels. But for now, for learning how to solder and basics about Voltage, Amps, Watts parallel and series connections, it was a great, great lesson.
Title: Re: First steps in using the Sun's energy
Post by: birrbert on February 10, 2014, 08:23:13 AM
Don't get me wrong, I wasn't criticizing your goal to learn or the viability of your project. I wanted to know about your expenditures so that I could compare with mine later when I make a calculation. Also, you wrote that Adafruit is not cheap. Well, I think it's affordable. As you say, when you hunt for components and do stuff yourself, you spend more than the cost of a ready made product and the only reassuring thing about it is that you learn (I consider it a school-fee). :)
Title: Re: First steps in using the Sun's energy
Post by: gording on February 10, 2014, 08:51:26 AM
You're right. At the the very end the most important for me is satisfaction. I can get no satisfaction ;) if I buy complete project from Adafruit. This one I've done from top to bottom by myself and I'm proud of it :)  Many of complete projects have a box with all the electronics and a solar array joined together. I specifically needed to hung the array outside of the window and because of the unfavorable geographical direction make it way bigger than it would come with of the shelf projects.
Title: Re: First steps in using the Sun's energy
Post by: birrbert on March 09, 2014, 04:57:02 PM
Some updates on this project

The solar cell phone charger started to take shape. At the moment I'm using my award winning DIY power supply to simulate the solar cells. I'm following the drawing posted earlier: Li-Ion batteries are being charged through the TP4056 regulator and a step-up converter provides 5 Volts to charge the cell phone. I made a battery bank out of four cell phone batteries, wired them in parallel, each around 1000 mAh capacity and charged it all the way up.

The 1350 mAh battery of my Nokia X1-01 was down to the level of 1 bar and with the first try I charged it up to 5 bars out of 6. Then I waited to go down to 1 bar again and with second try I gave it a full charge. After this the battery bank still had 3.6 Volts in it so I took a Samsung cell phone which barely turned on because of the low battery and I gave that one almost a full charge. That's when the battery bank depleted. Now I'm charging it back again to do some more testing.

I also encountered some problems or I should say "birrbert wasn't paying attention. :)
First, I killed one step-up converter. I didn't pay attention and I connected the battery bank to the converter the wrong way and it didn't work anymore. It's allowing electricity to pass, but it's not boosting. I went online for information and discovered that indeed they don't have reverse polarity protection. That's that. Luckily I had two: the green one is dead, the blue one is till OK so I'm using that now.
Second, I think I damaged the charge regulator. I wanted to check its temperature by putting my finger on the board, but unfortunately I was charged with static electricity and there were some serious sparks upon contact. Since then the LED of the regulator is green, which normally indicates that charging is done, but in reality charging is not done, the battery bank is still being charged, because I can see current draw on the LCD of my power supply. So, the LED should be red and turn green only when charging is finished. The LED remains green even when battery bank is not connected; in this case it should be blinking. Again, lucky that I have two more of this regulator, though they are different versions and this was the one I liked most. :-[

Lastly, I did a quick research on the Internet about step-up converters. Please find attached the .txt file which lists the boost converters I think can be useful. There are cheap ones that say they work even with an iPhone and then there are two more expensive ones from engineers I already mentioned in this topic. If you think I missed some, please post here.

In the next round I will prepare everything for a test out in the sun. I'll be back with photos too (my camera is not working at the moment). Cheers!
Title: Re: First steps in using the Sun's energy
Post by: SeanB on March 10, 2014, 12:34:50 AM
Smoke let out...... Probably cheaper to buy a new boost converter than to change out the chip on the board, which is the likely failure. Best is to place a 1n400x diode across the input to provide some reverse polarity protection, along with a fuse of around 5A. That will provide a reduced chance of blowing the module with reversed polarity.

Static damage is a problem, you need to look at doing static control, and if you have carpeting I would suggest taking a sprayer ( like a garden sprayer) and filling it with a solution of fabric softener ( 5l of warm water and 2 measures of softener) and spraying the carpeting with this. It works well to handle static build up, and makes the whole place smell nice. Clean carpets before hand, and if you can rent a wet extractor and do them you will pull out some brown soup as well. The softener also works on wooden or vinyl flooring, but there you will be best applying with a mop.
Title: Re: First steps in using the Sun's energy
Post by: birrbert on March 10, 2014, 07:20:47 AM
Thank you very much for the advice! I must take measures. As of yesterday, I wasn't concerned about static electricity, because I never did any damage with it, but now that I experienced it myself I have to be more careful.

The diode should be on the positive side or the negative side or it doesn't matter?
Title: Re: First steps in using the Sun's energy
Post by: SeanB on March 10, 2014, 09:40:17 AM
Across the power input so that it does not conduct unless the input is reversed. If you have old PC power supplies use the Shottky rectifiers from the 12V side as the diode, the low forward voltage drop and high current capability in a TO220 package will help to protect and blow the fuse, but in normal operation it will draw no power and effectively not be there. If you put it in series with the input you will have a loss across the diode which will be a concern in low voltage inputs like here, where you want all the power out of the cell.

If you look up you can also use a MOSFET as a protection diode, where it is run in reverse ( funny though that looks) and the gate is used to turn on the device when correct power is applied and short out the body diode. Simple and works with low loss. Old PC supplies will also have the MOSFET in them on the 3V rail.
Title: Re: First steps in using the Sun's energy
Post by: birrbert on March 23, 2014, 07:25:19 AM
Hi! Yesterday and today was a great day. I got sunshine and time to play with the solar cell phone charger. To be precise, I tested only the first part which is the battery bank charger. It's working as expected. In unobstructed sunshine the panels provide 580 mA which is great because it's very close to the claimed 600 mA. The Voltage was at around 4.5-4.6 V, which is a bit lower than the claimed 6 V, but I don't mind until the TP 4056 based charge controller is OK with this.

When I started charging today at around 10 AM the battery bank was down to ~3.3 V and now after ~3 hours is closing up to 3.9 V. Yes, it's not so great, but there wasn't full sunshine because of them clouds. I'll have to invest in some more powerful solar panels or cells. Since I don't have any image recording device at hand that's all I can present for now. Enjoy the rest of your Sunday! :)

Cheers!
Title: Re: First steps in using the Sun's energy
Post by: MJLorton on March 24, 2014, 02:21:37 PM
Hello Robert,

Good to see you are playing with the solar charger again...I've started playing with my solar powered Kindle again and will be posting some videos about it soon.

Cheers.
Title: Re: First steps in using the Sun's energy
Post by: birrbert on March 25, 2014, 03:28:03 AM
Wow, that's great news! Looking forward to it! :)
Title: Re: First steps in using the Sun's energy
Post by: birrbert on March 26, 2014, 11:04:44 AM
I'm getting around 20 mA on cloudy days at around 4 PM. It's slowly decreasing, 15 ... 13 ... and finally 0 until it get's dark, I guess. :)
I will let the panels charge right until the evening because I'd like to see how does that charge controller act in darkness.
Title: Re: First steps in using the Sun's energy
Post by: birrbert on March 29, 2014, 03:46:26 PM
After two and a half days testing I can say that the system is working well. The panels needed this amount of time to charge the battery bank from ~3 V to the full 4.15 V. One full day was cloudy and the rest was sunny. Now at least I know what the situation is in the area where I live. It would've been nice to log some data that I can present here, but for now that's not possible. Also, I must mention that I'm not sure how many mAh's can my ad hoc battery bank hold (four cells used in Nokia 7210).

OK. That's about it for now. I'm a bit unsure which way to go from here. I'm planning to buy a good 4400 mAh rechargeable battery and I'll put the cells in a fabric casing thingie. Oh, and of course I would like to try out more powerful solar panels, e.g. three 500 mA @ 6 V wired in parallel.
Title: Re: First steps in using the Sun's energy
Post by: MJLorton on April 03, 2014, 09:56:23 AM
Interesting Robert. I have to say, it is frustrating finding a reasonably priced device to measure power and energy (Ah and Wh) and log it. I've been chatting to someone about designing such a device...will see where that leads.

Cheers,
Martin.
Title: Re: First steps in using the Sun's energy
Post by: birrbert on May 15, 2014, 05:19:05 AM
If found another interesting piece of equipment today.

I. Lithium ion 5V 2.1A USB Boost Charge Board iPhone Capacity LCD Mobile power
Link: http://www.ebay.com/itm/Lithium-ion-5V-2-1A-USB-Boost-Charge-Board-iPhone-Capacity-LCD-Mobile-power-/171319321551?pt=Battery_Chargers&hash=item27e36d63cf

I will buy one and try it out, but if anybody here thinks it's a good idea, you can test/review one too.

Other versions:

II. Lithium ion battery 5V 2A Dual USB all-in-one boost charge iPhone capacity LCD
Link: http://www.ebay.com/itm/Lithium-ion-battery-5V-2A-Dual-USB-all-in-one-boost-charge-iPhone-capacity-LCD-/111087745765?pt=Battery_Chargers&hash=item19dd587ae5

III. 1.2" LCD Dual-USB 5V 2.1A Boost Board PCB DIY Module w/ LED for Mobile Power
Link: http://www.ebay.com/itm/1-2-LCD-Dual-USB-5V-2-1A-Boost-Board-PCB-DIY-Module-w-LED-for-Mobile-Power-/321181410160?pt=UK_BOI_Industrial_Automation_Control_ET&hash=item4ac7e76370
Title: Re: First steps in using the Sun's energy
Post by: MJLorton on May 20, 2014, 12:10:10 PM
Interesting little chargers....will be keen to hear your thoughts if you get one.
Title: Re: First steps in using the Sun's energy
Post by: birrbert on October 21, 2014, 11:38:56 AM
Hi!

Disregarding the warning that says "this topic has not been posted in for at least 120 days." :)

Family is priority, so once again I've been drawn away from my hobby for several months, but I did manage to buy the first Lithium Ion charging board. I've used it for a while now and it's good, usable. My experience is subjective since I didn't take any serious measurements, but I'll hopefully manage to buy a meter with basic logging capability and check the efficiency of the board. For example THIS ONE (http://www.ebay.com/itm/LCD-USB-Mini-Voltage-Current-Detector-Mobile-Battery-Power-Charger-Tester-Meter-/381006430622?pt=AU_Components&hash=item58b5c0c19e) was presented by a good ol' English man, Julian Ilett, on his YouTube channel.

The charging board physically comes in two pieces, identical in size, which connect together via some pins. Maybe this board wasn't intended for an end user, but if it was then it's a bad idea, because the two pieces wiggle and bend and twist too much, there's nothing to hold them strongly together. So, this would be a negative point. I'll point out that versions II and III have a different structure so I'll make a comparison when I have one of those in my hands.

I remain at the drawbacks and quickly mention that I found the LCD to be a very good idea, but the one they used with this charger board is not the best. It's usable, but quite hollow. The back-light has a strong blue color, but at least it helps to read the information. The display is controlled by a 12 bit analog to digital converter and shows the charge state of the battery in percentage, has a bar graph too in this regard and shows the output current.

Technically, the board does what they say: uses a 5-6 Volt input to charge a Lithium Ion battery and then boosts the electrical energy coming from the battery to deliver a stable 5 Volt output. On the input side it has a micro USB port and on the output side a regular female USB socket. It has the necessary resistors to charge iPhones or other sophisticated smartphones, tablets and gadgets. Over-voltage and under-voltage protections are a must. I believe what it doesn't have is reverse polarity protection so one must be careful when connecting the battery to the board.

I bought a Boston Power Swing 4400 battery: http://www.boston-power.com/products/swing-4400
Datasheet: http://www.tme.eu/ro/Document/a6369bd7221221e62bfbb11b3daf3733/ACCU-18650X2_BP.pdf

It seemed like a good choice for about 10 USD. What I found extremely difficult is soldering the cable to the positive terminal. The metal part there is about 4 cm x 1 cm and I was having a hard time getting the solder to stick even with my 3 mm chisel tip. First I tried with 350 degrees Celsius which is the usual temperature I utilize when soldering, but I had to go up to 450 degrees and then I managed. Although I succeeded in the end, I think I put the battery through a lot of stress. Unfortunately, the whole body of the battery got heated up several times so I'm pretty sure its life-cycle got reduced. After this procedure I did some reading and I realized that in fact I should be happy that it didn't explode in my face. So, everybody, be careful when soldering directly to battery terminals! If there's a possibility, don't do it, try other/safer methods. If you really have to do it, then do it with a very hot iron, choose a large enough tip and make very short (i.e. 2 seconds max) contact. I'll be honest and say that I don't know of other possibilities for home DIY people, so if you know of some techniques, please share.

Since I still lack a HD video camera, this would be a brief description regarding this type of Lithium Ion charging board. I connected my small solar panel to it and it charged the battery quite well. Photos below.

- Board A one side - http://i.imgur.com/6qARDKw.jpg
- Board A other side - http://i.imgur.com/NrIbdTH.jpg
- Board B one side - http://i.imgur.com/Poqc4Bz.jpg
- Board B other side - http://i.imgur.com/iI0VULA.jpg
- Assembled one side - http://i.imgur.com/asazLaK.jpg
- Assembled other side - http://i.imgur.com/VK9JMLy.jpg
- Assembled positive terminal - http://i.imgur.com/xkZSQbo.jpg
- Assembled negative terminal - http://i.imgur.com/sgfF12p.jpg

Please let me know what you think. Cheers! :)
Title: Re: First steps in using the Sun's energy
Post by: SeanB on October 21, 2014, 03:06:23 PM
I think those terminals were designed for spot welding of a thin strip to, rather than for direct charging. Well done though on making it though, should be a nice charging station.
Title: Re: First steps in using the Sun's energy
Post by: MJLorton on November 03, 2014, 02:11:56 PM
Totally respect your priorities...at the moment here it's family...and clearing the never ending piles of leaves! Fun, fun!
Good work...looking forward to seeing  / hearing how well it operates.


Title: Re: First steps in using the Sun's energy
Post by: birrbert on November 03, 2014, 02:51:00 PM
Yes! Especially valid for me, young father, who has to acquire new time management skills now. :)

Sorry for my slow reaction SeanB! I read something short about spot welding, but it didn't sound to me as a home DIY thing. I would need a solution for this, because I'm planning to build a bigger capacity charging station and I have no other idea than soldering.
Title: Re: First steps in using the Sun's energy
Post by: SeanB on November 03, 2014, 03:01:43 PM
Look for some really big high current capacity high voltage capacitors, like 4700uD 450V, and you can build one using them, or using some 1F 16V car audio capacitors ( but be aware of the fake ones out there as a lot are fake units in a big case with a rock inside to add mass) for a low voltage one, then you can build your own.

Gotta get off my ass and finish the one I was planning to build, got as far as winding the transformer for it.
Title: Re: First steps in using the Sun's energy
Post by: SeanB on November 03, 2014, 03:03:09 PM
Totally respect your priorities...at the moment here it's family...and clearing the never ending piles of leaves! Fun, fun!
Good work...looking forward to seeing  / hearing how well it operates.

In 2 months while I am enjoying the sun you will be building snowmen. ;)
Title: Re: First steps in using the Sun's energy
Post by: birrbert on February 02, 2015, 03:57:43 PM
Hello!

Still on this topic, learning every time I have the chance. :)

I didn't like the efficiency and the build of the first all-in-one charging board so I bought the second type that I mentioned back in post number 60. This has a much better build quality, dual output and better efficiency. I also bought a a KCX-017, the USB power monitor mentioned in post number 62.

So, if it's of any value, here are some measurements:
- charging my Lithium-Ion pack needed 4526 mAh which means 16.7 W at 3.7 V nominal Voltage
- while discharging the pack provided 2960 mAh meaning 14.8 W at 5 V
- if I calculated correctly, that means an efficiency of 88.6%

Discharging was done with a small 4.8 V / 710 mA incandescent light bulb. Next I'll see if I can test this thing in a more realistic situation, i.e. charging cell phones, USB gadgets, etc. Plus I'm still planning to make use of the small solar cells and create my own custom portable small solar powered back-up. I'll get there sometimes. :)