Solar Shed Project

[albertc30]

Hi all.

Seen many videos about solar installs.

I am only after having some lights in my shed, for the rare occasion I do go there at night.

In all, here's a power consumption of all the things I wish to power up.

1. 10W flood light with PIR sensor, stand by: 0.052A, Operating:0.438A
2. 8 X 16Led lights, Operating: 0.85A
3. 12V Relay, Operating: 0.096A (3 relays in total, only one operating at any one time)
4. 12V temp. controller, Stand by:0.02A, Operating: 0.073A
5. 12V Dusk / Dawn switch, Stand By: 0.005A, Operating:0.039A
6. 12V Water pump, Operating:0.37A (2 water pumps, one to top up water tank, very rarely on, the other to run water flow to heat water to 30C. Will operate once water drops below 20C and stop when 30C reached. Water circulates through 4mm inner diameter inside empty water bottles exposed in the sun.)
7. 12V Led light (Red, Yellow and Green, to monitor tank and are activated by relays. Always one on. Operating: 0.024A
8. USB / 12V Power Socket, Operating: 0.027A
9. 12V Buzzer, Operating: 0.026A (Bypass switch, this works as a reminder, once the door is opened, that the lights are on. Don't want to discharge the battery.)

I have a 20A MPPT charge controller that I bought on eBay. It looks, according to a video on YouTube, that it is a cheap Chinese fake and now it seems to be busted. The assumption is due to my 12V 22ah battery has bubbled up and I was told it was due to overcharged.

I am now on the hunt for a new charge controller and a new battery.

To my calculations, a 22ah agm battery is more than enough for my needs.

I have 2 solar panels connected in parallel, 100W + 25W at 12V, so a total of 125W.

I am tempted to buy the New Model Tracer1215BN PV Panel. The website is rating this to a total 130W array, so I am just within and I shall have a 10A or 9A even fuse between it and the solar panels.

Any ideas or input about this controller? Any good? Or is it too much to what my needs are really?

In terms of battery, a 22ah should be more than enough really. I have calculated the size to a DoD of 35%.

Any comments and/or help are truly appreciated.

Regards,
Albert

[MJLorton]

Hi Albert,

Sorry, from the attachments I can clearly understand what your total energy usage will be. But if you have a good 22Ah AGM battery you could use 45% of the stored energy (264 Wh) which means about 118.8 Wh. Cater for some losses and call it about 110 Wh you'll have to use. If that's not enough for your needs you'll need a larger battery.

Don't connect unmatched solar panels to an MPPT solar charger. It can't find the maximum power point for two dissimilar panels. Also, I would stick to known name brands for MPPT charge controllers...at this point in time I don't know of any good cheap MPPT charge controllers.

Hope that helps.

Cheers, Martin.

[Free Energy Freak]

To my calculations, a 22ah agm battery is more than enough for my needs.

I have 2 solar panels connected in parallel, 100W + 25W at 12V, so a total of 125W.

I would drop the 25 watts panel, buy a single 50AH battery (you know you are going to add something later.), a decent MPPT or PWM controller, and let the 100 watts panel charge that battery. Your 100 watts panel should turn out about 5.5 amperes, which will give you a good 10% charge rate to that battery.

I am tempted to buy the New Model Tracer1215BN PV Panel. The website is rating this to a total 130W array, so I am just within and I shall have a 10A or 9A even fuse between it and the solar panels.

Any ideas or input about this controller? Any good? Or is it too much to what my needs are really?

Sorry to offer tough love here. But, Albert, you already lost one battery due to buying Chinese junk. Why possibly repeat the issue with more junk? You want your system reliable, so it provides the power you need, when you need it.

I would suggest buying ONLY quality parts. You get them from quality suppliers - Midnite Solar, Outback, Rogue, MorningStar, or maybe a Steca?

[tillt]

I reccomend you to get the Mppt some good brand, because the Chinese MPPT are almost always just a PWM...

[PoBoySolar]

A PWM controller is perfectly acceptable for a 12V array into a 12V battery. MPPT
only has a very  when marginal improvement when array and battery are 12V.  It is not
an engineering blunder that the listed power point of a panel is around 18V.  That is
at 25C and in the summer that can easily drop to under 16V. Even a battery needing a
charge easily rises to 13.5V or more at low charging currents. Given some diode drop,
wire loss and SMPS converter efficiency, The advantage of MPPT is rather minimal. The
vendors all do number tricks like quoting 95% and even one used 11.5V as battery voltage.
This all changes if a 24V or higher array is used to charges 12V battery.

Unless your system is greatly under powered, a large portion of potentially harvested
power will just be wasted. My off grid camp only has about a 1000W array and I a able
to divert about 2500WH a day to heat all the water I need. I heat water with MPPT, any
other way and the losses would be very dramatic.  I design all my own equipment and it
operates at power point.  In an active system like mine the controllers never really
get beyond bulk charge.  This is the type of charging based on constant voltage common
in automobiles.  A shed lighting system is mostly standby and charging voltages must be
lowered to prevent boil off after the bulk charge phase.

I use a car batteries, a big no no. It is from a vehicle I don't bring with my for that
time period.  These are not rated for deep discharge and the system is real time, only
using the battery for surge currents.  More than a 20% discharge is not allowed.  It
works well because it is an engineered system that prioritizes loads and schedules them.

Here are a couple of pictures of my solar shed. It has a 9 and a 20 gallon water heater in series.