Off grid D.I.Y. solar system for the allotment shed - using re-cycled parts - how to do it

Setting up a small solar system is easier and cheaper than you think, especially if you use 2nd hand or discarded panels.

i was recently given 2 100w solar panels. the glass on the outside of the panels is broken and shattered, however they still work. They give slightly less voltage but that voltage is still more than we need.
The panels were originally from a boat fitters yard, and as they had been broken they could not fit them to a boat and then charge the customer for them. the company just wrote them off .
so keep an eye out for damaged panels, mostly they still work and you may be able to get them free or very cheap.

These panels are perfect for a 12 volt system. the voltage on the panel is higher than 12 volt but we will use a charge controller to step it down. the actual voltage measured from these panels is on average 17 volts.

As we have 2 panels, we need to wire them up together.
We have 2 options for connecting the panels. Series or parallel.
basically if we wire in series we will double the voltage. If we wire in parallel we will double the ampage.
we dont need more voltage because when you charge a 12 volt battery you usually only charge it with a charge of 2 to 3 volts higher. the charge controller limits the amount of voltage coming in to the batteries.

So we wire in parallel. WARNING : CONNECT BATTERY BANK TO CONTROLLER BEFORE CONNECTING PANELS TO CONTROLLER.

We also need a charge controller.
Charge controllers vary in price from a few £'s to hundreds of £'s
After a bit of research i found that if you are buying brand new expensive panels and expensive solar batteries then you will want to spend more on your controller so your system runs at its most effiency and keeps the battery life to maximum.
As our project is using brocken panels, re- purposed car batteries which are not identical i decided to go for a cheap controller.
If its not sufficient in the future we can always upgrade. but as this is an experimental project which is just low powering the allotment shed and is not a critical system then i think this will suffice atm

Anself 10A/20A 12V/24V LCD Solar Charge Controller With Current Display Auto. (£12.99 from ebay)

As mentioned before, we connect our battery bank first, in this setup we currently have 2 batteries in parallel which keeps the voltage at 12 volt. (you can add more batteries)

Now you can connect your panels to the charge controller. there is also a load connection on the charger which you connect your circuit that you want to use. on our circuit we have a 12 volt cigarette lighter connection which we can also plug in a usb adapter or an inverter (giving 240v)
Also on the charge controller there are 2 x 5volt 2amp usb connections. these days you can get plenty of things that connect via usb, i.e. LED lights, phone and tablet chargers, fans, radios. we are even using 1 of our usb connections to run a raspberry pie and broadband wifi system. (i will be posting a d.i.y. on that soon)

So now we have usable electricity in our allotment shed. we no longer need to take the batteries home and charge them.

I hope this post is of help to others wanting to have a go.

I have to admit electricity is not my strong point and i was bewildered on how to set this system up to begin with. so if ive missed anything or anyone can advise how to do it better then please leave a comment.
thanks :-)

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