Solar Question

Greggbear67

Full Member
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
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
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.
 

wildebus

Full Member
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
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.
 

wildebus

Full Member
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)
 

Greggbear67

Full Member
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.
 

wildebus

Full Member
Im running 200w panels into 180ah batterys and my solar reg will trickle charge eng batt as well
depending on your split-charge system and also your general use, a second output may or may not be useful.
If there is a bi-directional voltage sensing relay (VSR) fitted, that will switch on once the leisure battery has reached a certain voltage (usually around 13.3V) so this second output is defunct.
If you have a B2B, then chances are there is no 'reverse' charge from solar to starter battery and some method of trickle charging the starter battery is handy.
It can be better to have this separate from the solar controller anyway as that way you will get a charge to the starter battery from EITHER the solar OR a mains charger plugged (so at home or on EHU) if that second output only works when PV power is present.

For me, that second output would be superfluous as I have a Battery Combiner (Victron CT-230) which is bidirectional and engages automatically at 13.3V. So when I plug in EHU, or have solar, my Starter Battery gets a controlled charge whenever power is coming in.
 

mistericeman

Full Member
I saw a few sites where some diyers replaced their 240v fridge compressors with the efficient, variable speed 12v Danfoss compressor. Might be worth a Google search?
https://www.danfoss.com/en-gb/products/compressors/dcs/compressors-for-refrigeration/mobile-dc-cooling-compressors/
Trouble is unless your a qualified fridge engineer, then by the time you have bought the 12v compressor and paid someone to reclaim and recharge the system.....
You probably not far off the cost of a bought 12v fridge
 

NickB

Full Member
Yes could be... but lots of "professionals" over egg their skills. I NEVER attempt anything until I know or have practiced the principles. If we listened to the "professionals" most of us wouldn't attempt a full van conversion.
All the refrigeration kit is available on line, tons of you tube videos.
Silver soldering was something I learned in metalwork in school. Recharge kits are cheap as chips.
If you cock it up.... blaaa... you have to start again. Practice on a few scrap compressors would be an idea.
Always amazing how black arts are black arts until you learn the tricks. Hardly worth an apprenticeship.
We have ALL seen amateur cock ups and amateur work which betters so called "professional" work.
I taught ALL my kids early that professional only means getting paid for doing something. It's no guarantee of a good job. Word of mouth, quality and cost follow artisans.
Those are my principles and if you don't like them... well I have plenty of others. GROCHO MARCS
 

mistericeman

Full Member
Yes could be... but lots of "professionals" over egg their skills. I NEVER attempt anything until I know or have practiced the principles. If we listened to the "professionals" most of us wouldn't attempt a full van conversion.
All the refrigeration kit is available on line, tons of you tube videos.
Silver soldering was something I learned in metalwork in school. Recharge kits are cheap as chips.
If you cock it up.... blaaa... you have to start again. Practice on a few scrap compressors would be an idea.
Always amazing how black arts are black arts until you learn the tricks. Hardly worth an apprenticeship.
We have ALL seen amateur cock ups and amateur work which betters so called "professional" work.
I taught ALL my kids early that professional only means getting paid for doing something. It's no guarantee of a good job. Word of mouth, quality and cost follow artisans.
Those are my principles and if you don't like them... well I have plenty of others. GROCHO MARCS
I don't doubt it's doable by many (it's not rocket science after all).....
However unless you're Fgas qualified and registered...
Legal wise you shouldn't be working on CFC/HCFC systems.
But don't let safety and environmental concerns get in the way eyyy?

I can buy a 12v Danfoss compressor for less than £50 (generic copy even less)
And have the qualifications and reclaim kit to swap out a 240v compressor for 12v.....
Most folks won't....
So will possibly vent r134a/404a/1234a to the atmosphere...
Knacking the ozone layer etc for the rest of us AND their kids with abandon.
 

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