Solar Question

#1
Looking at solar panel kits. 2x100watt panels & 20a controller. Noticed the descriptions say only suitable for charging 2 unconnected batteries. My question:- would this type of kit be suitable to charge my 2x110ah leisure batteries that are connected together? They are wired +to+ &-to- with the earth taken from batt1 & positive taken from batt2. How would they need connecting to a solar supply?
 

Squiffy

Full Member
#3
Greg you have them in parallel which means that you have basically got a single battery of 220ah so your panels would take in theory twice as long to charge up as charging a single battery of 110ah, but in all honesty with two panels off 100watts and a controller of 20amp rate my view would be it will be fine to use. Bearing in mind that the 100watt panels will not be punching their max ampage all the time as the sun is paramount in giving max amps/volts. It would also be dependent on what 12volt equipment you intend to use. Phil
 


NickB

Full Member
#4
Take a look at the LG Neon 2 solar panels when making your choice 335 watts + if you have the roof space, that's the panel I bought.
 


#5
The general rule of thumb with solar is 1W of Panel to 1Ah of Battery. so a 200W Solar Array to feed a 220Ah Battery Bank, with a 20A Controller is nigh spot on that 'rule' for most users (y)

Very simple to wire up:
- 2 panels will be wired up either series or parallel. Parallel is same as you have done your two batteries and you buy a MC4 "Y" Connector to make the parallel connections; Series is +ve on Panel A to -ve on Panel B.
Whichever way you do it, you end up with two loose cables - one +ve and one -ve - that go into the van and connect to the Controller "PV" connection. You will almost certianly need extension cables - you can get off the shelf ones with MC4 connectors one end (for the panels) and bare the other (for the controller).
The Controller will have a "Batt" connection - you connect that to the battery - +ve to +ve, -ve to -ve - and job is done.
NOTE: some controllers require the connections to be made in a certain order. You usually should connect the battery to the controller before the solar panels to it.
The Controller may also have a "LOAD" Connection. Generally just ignore that.

Don't expect 200W from the Solar except for very brief times - in the summer months at high noon on a cloudless day that isn't too hot.
If you can achieve 500-800Wh of charging a day in the UK summer (depends on cloud and rain) that is pretty ok (a 110Ah Lead Acid Battery at 50% charge will have provided around 700Wh of energy so don't expect to recharge your 220Ah battery bank from 50% to full just from Solar in a day).


Couple of additional comments:
1) Get an MPPT Controller and wire the panels in Series for the optimum results
2) A PWM Controller will still work, albeit less efficiently and if you do go PWM, you must wire the panels in Parallel otherwise you will waste a lot of potential solar harvesting
 


NickB

Full Member
#6
Agreed entirely with the above. I went for 335watts to compensate for the harvesting losses which occur because the panel is always flat.
*TIP....*
when you buy the MP4 extension cables.
It's usually cheaper to buy one M/F extension and cut it half than to buy two leads M to bare end and F to bare end.
 


#7
Agreed entirely with the above. I went for 335watts to compensate for the harvesting losses which occur because the panel is always flat.
*TIP....*
when you buy the MP4 extension cables.
It's usually cheaper to buy one M/F extension and cut it half than to buy two leads M to bare end and F to bare end.
Ref tip ... good idea :). When I supply a kit, instead of a pair of cables (+ve and -ve) I provide a single cable with a connector both ends. That way, it can be cut into the lengths required and you end up with a longer single length left over instead of two short ones. Handier for using elsewhere (such as connecting controller to battery)
 


#8
Thanks guys, lot of helpful info there. Only really got 6 led lights to run plus a couple of ish charging points for now but looking to fit an inverter & small 240v fridge soon.
 
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