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Hi all,

Ok a winter project idea which I need some advice on. I am thinking about building a seperate box on the front arms of our trailer to house 2 x 110AH leisure batteries. Then with them wired in parallel and charged via the twin electrics on the tow bar I had planned to mount our inverter within the box and wire the inverter to an EHU socket through the outer wall of the box so we can plug our mains hook up lead into the socket on the trailer.

Q: Will the EHU lead that we have with its RCD work or will I need to use a standard extension lead and change the plug ?

Also I had thought about fitting a solar panel on the lid of the trailer to charge the batteries when not hooked up the the car but not sure if this is really worth the expense ?

Any advice would be great.

Thanks

Gary

You will probably have problems with the nose weight of the trailer as 110v leisure batteries are very heavy.

John

Not sure about the RCD from an invetor. Prob best to ask on an electrical forum. Or if you have the invertor, just try it!

I do like this idea tho! It allows for using not ehu campsites and brings down the long term costs.

I was looking into this a little the other week and thought a 60W panel should do, based on running a 12v 5 amp fridge. But if you could run a smaller pannel the cost would come down a lot. I guess if you use the car to charge the batteries when on local trips aswell it help.

As above but you could counteract this by loading heavier stuff towards the back of the trailer (obviously within its limitations).

Perhaps more fundementally, unless you are going touring (ie packing up and moving site regularly) your batteries will only be charged on the way there and back (if you charged them at home they would be fully charged anyway).

I camp for up to 3 weeks on batteries and have 3x strip lights, LCD TV, water pumps to kitchen and WC taps, electric flush WC, 12v vacuum cleaner and a few other bits and pieces. I have a bank of 2 or 3 leisure batteries but I charge them in the car via a smart charger run from an inverter powered by the cars alternator. I alternate the batteries every few days (running 2 in parallel still only gives you 12v and they will both go flat at the same time, even if it takes twice as long), quick release connectors allow easy swapping. I always have one battery in use and one in the car (properly secured) charging up. I have a rough idea of how much my electrical items consume and aim for my batteries not to discharge below 1/3 of their capacity to ensure a long service life. 

Regarding plugging an inverter into your battery bank; inverters are quite inefficient and will use 10-20% of your precious capacity - consider direct 12v items wherever possible. An inverter produces "real" mains voltage so you would still need your existing protection. 

Personally I dont believe solar panel are cost effective yet, with my (relatively cheap)set-up as above I can put a theoretical 16amps an hour back into my battery.

Chris.

Thanks guys,

Thats given me a few things to think about. May well just run the inverter for the TV and run the rest on 12V, lights, cooler box etc. I wasnt planning on running anything heavy like heaters or kettle, will stay with the gas for these. We have both 12 and 240V kit anyway from the days before we went the EHU route.

The point about nose weight of the trailer is a good one although if I build the box within the trailer and balance the weight when loaded this should be ok I assume.

I think a solar panel is a bit overkill so scrapped this idea, after all if I need to top the batteries up I can just hook up the trailer and charge them from the car. I was just trying to tidy things up and make life a bit easier as it takes us longer to unload and set up the tent than it does to pitch it and I wont have to keep lugging batteries about and charge them before each trip, I can just leave them in the trailer and just plug in.

Thanks again

Gary

Hi Saxo1,

Thanks for that, its obviously very good advice but you have lost me !! Are you saying I need to take the inverter apart and check to see if its wired up in the way you suggest and if not to do so or do I just leave it alone ?

Please remember though that I am not a sparky so go slow and in plain english would be great.

Thanks

I was looking into this a little the other week and thought a 60W panel should do, based on running a 12v 5 amp fridge.

Are you talking about a fridge (which only runs part of the time) or a coolbox (which is on permanently)? If the former a 60w solar panel will help, if the latter your battery will still go flat quite quickly!

A 60w panel will give about 20Ah per day in summer, a 5A coolbox will consume 120Ah. You'd need 200Ah of batteries (2 110Ah ones) just to run the coolbox for 24 hours.

Have a look at...

www.glenp.org.uk/batteriesfaq.html

It's still a work in progress but it's something I'm putting together to answer some of the questions that keep coming up!

Glen

Quote: Originally posted by cdbe on 16/11/2009

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As above but you could counteract this by loading heavier stuff towards the back of the trailer (obviously within its limitations).

The heaviest weights should always be loaded over the axle. Although the trailer maybe shorter than a caravan the effects can be the same. loading a heavy weight at the front and counter balancing it at the back will cause the pendulum effect.

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