Mini solar flashlight teardown

[Kiriakos GR]

Just got today this mini solar flashlight for just 1 Euro from a local bazaar.

The light beam were so bright and with great coverage at 5-7 meters away,
and interestingly enough it is very wide too.

Well I do not like to take things apart, but my curiosity of what type of battery is inside it did break every record.
What I found inside is a Lithium cell that is not famous for their recharging capabilities.
The solar panel it does work, and it produces 5.5V just by indoor strong light .
Even so with out the battery, those LEDs they do not operate at all.
About external construction it is totally unprotected about humidity.

The truth is that there is out there rechargeable coin batteries which are used in digital cameras so to keep the calendar alive,
but they are made by two manufactures worldwide, and they cost about 8$ USD.
   
For the price I should not have major expectations, but even as education it is good enough.       

Enjoy the pictures!

[MJLorton]

Your first step into solar energy...I love it! Make it a big one Kiriakos and do some more! (I know you would do a great job.)

Ok...very interesting...can you choose your "meter of the day"....and measure how much current it manages to push into the cell....or does it not recharge at all?

Cheers,
Martin.

[SeanB]

If you do do that make sure it is on something non flammable. I have popped a few coin cells just by shorting them, charging till they explode should be fun.

[Kiriakos GR]

You are both bad boys   

Interesting enough this simple design it supposed to keep the battery just topped up,
the inner battery resistance it would probably consume by it self the most of those theoretical 45mA
that this little panel it can theoretically supply. 

What is the true question here is the life cycle of the battery under those conditions.

Again in theory this item it can operate for 2 Hours (if you have the patience to have your finger pressing the little button that long )
And in theory, it will fully recharge in 5 hours.

Ok do not laugh at my face, I do not believe this fairy tale too.
Even so it is nice as inspiration     

Specs:
# 3 LED's powerful brightness  15000mcd
# Low power consumption
# ON/OFF switch
# 45Mah solar panel

[SeanB]

LEDS - very overdriven and going to fail soon
high power for the coin cell
easy to push by accident in pocket
In earth orbit perhaps, and cooled down as well.

Seen similar, but have just made a nice little one out of a dead mining lantern. Tried to recover the lead acid cells but nothing even with a 17V charge for 6 hours. When I gently opened the cells ( wanted to keep the housing intact) found the internal connects had corroded open, so took the plates out, neutralised the acid with NaOH and bagged and recycled them. Put a cheap 3 pack of 750mAh lithium cells in ( chinese cellphone batteries) and a simple charger, and a 1W LED lamp in the head, and a simple resistive current limit. Runs nice, with a lot more light from under 1W than with the original 1.6W lamp.

[Kiriakos GR]

Well if those LED fail one day, then I will probably try to use it at the top of my U1272A, so to contribute in the charge level of the inner NiMH.

Martin is good at spreading wild ideas. 

[SeanB]

Here is mine....... A lot lighter than the original, and I have used it already the day I finished putting it together.

[Kiriakos GR]

Well it looks that I got in to the game too. 

This little devil at direct sunlight it produces 7V.
With reflective sunlight 6-6.5V

I had to remove the battery at my testing about measuring volts.

After testing the battery with my digital battery tester, it shown  100% power at 3.8V (the tester uses always a load depending the battery type)
The voltage looks much higher than the 3.6V, and so yes it is get overcharged all the time, by this simplistic design.

The next test will be to see what it can do about charging the four AAA in my Agilent multimeters.
From the results (current measurements) I will make my mind if it worth to make a personal mini patent,
about keeping this little panel permanently at the top of the meter. 
If I succeed I will sale it to Agilent 


It is tremendously hard to take a good picture of those OLED's,
the display haves an inner refresh rate and you have to lower down the digital camera speed so come in sync.   

[SeanB]

Repeat that test with a 10R resistor across the panel leads and you will see that in reflected light it will output mA of current and only 700mV at best in direct sunlight.

[Kiriakos GR]

I did manage to set the U1273A as voltmeter and the U1272A as current meter but I lost the sun (sundown) 

By bypassing the on board switch and having in line the U1272A, I can see the mA that those LED needs.
More testing tomorrow. 

With true sunlight even as direct or reflective, those LED they did manage to light up, just by the panel.

By the way R=V/I    7V / 45mA (0.045A) = 155 Ohms 
 

[MJLorton]

Well if those LED fail one day, then I will probably try to use it at the top of my U1272A, so to contribute in the charge level of the inner NiMH.

Martin is good at spreading wild ideas. 

Cheeky man! 

[MJLorton]

Well it looks that I got in to the game too. 

This little devil at direct sunlight it produces 7V.
With reflective sunlight 6-6.5V

I had to remove the battery at my testing about measuring volts.

After testing the battery with my digital battery tester, it shown  100% power at 3.8V (the tester uses always a load depending the battery type)
The voltage looks much higher than the 3.6V, and so yes it is get overcharged all the time, by this simplistic design.

The next test will be to see what it can do about charging the four AAA in my Agilent multimeters.
From the results (current measurements) I will make my mind if it worth to make a personal mini patent,
about keeping this little panel permanently at the top of the meter. 
If I succeed I will sale it to Agilent 


It is tremendously hard to take a good picture of those OLED's,
the display haves an inner refresh rate and you have to lower down the digital camera speed so come in sync.

I love it! It just makes so much sense to me....one fine day we'll see a brand name or good quality multimeter backed up with solar power!!! 

Get that patent in quickly.....! 

[Kiriakos GR]

Oh my...  those 1 Billion Chinese people they did scammed me for once more time. 

This panel all that it can do is to deliver 2mA at max by dropping down the voltage to 2.6V.

I just lost my chance to become a millionaire from the Solar business   

[Fennec]

>This panel all that it can do is to deliver 2mA at max by dropping down the voltage to 2.6V

lol, what you expected for ? 2A ?
Check out that cheap solar garden lamp panels for maybe $US 5. Two of them should be enough power for your Multimeter if u use SuperCaps like Martin. But really. I pay for 10 AAA Cells (Duracell) 1,95€, So why the heck I should to be irritated with this stupid Solar and set my DMM always behaved in the sun ?
Solar is still too expencive. Maybe in 50 years...   

Did u measured how much current your DMM need ?

 

[Kiriakos GR]

All that I had in mind was this little panel, to fight back the self discharge of those NiMH when the meter are not in use.
Something equal to trickle charge.

I was not that optimistic that this panel will keeping alive the multimeter just by it self.

If this panel it could deliver 5.2V and 20mA I would be more than happy.


EDIT:
One last picture from the panel.
Probably the part code it can lead to some real electrical specifications.
I will try that next. 


EDIT: No2  the 40mA are the inner battery specs. 
If he is a serious manufacturer ?  I am a Lord from London again. 

http://qf-solar.en.alibaba.com/product/390418541-209457701/solar_torch.html