Leisure to main battery wiring.

[Veronica Walker]

Help me please. I have a converted camper, had help with wiring leisure battery to main battery, but this caught fire recently and was told by RAC that it had been a botch job.
What I want to know is all the what? whens? hows? and whys? of rewiring this, that is what breakers and stops etc, also what is the best wiring required, are needed and how they are done. I understand that there is a non-return voltage component that would be needed, names etc. would be needed.
Appreciate any help, please.

 

[harrow]

As you have found out that there is a real fire risk because of how many amps could be involved.

Please get someone who knows what they are doing to complete this job.

:yeahthat::yeahthat::yeahthat:

 

[hairydog]

The vital thing is the fuse rating. The purpose of a fuse is to stop the cable catching fire. The fuse should be the size that blows if the cable is overloaded.
Most motorhomes have an undersized cable protected by a fuse, usually a 20A fuse.
To do it properly, you should install a battery to battery charger, but they cost around £300. Next best is a split charge relay. They cost about £1 if you get a good one at the right place.
The cable needs to be at least 6mm^2 cross section, though I'd use much bigger. The fuse rating needs to match the cable size.

 

[Wanderer015]

This is what you need, a proper split charge kit

PROFESSIONAL SPLIT CHARGE KIT 2MTR 12V 140A AMP RELAY 110AMP CABLE HEAVY DUTY | eBay

 

[Admin1]

Please also remember that it must be fused at both ends as there is power at both ends.

I draw you a picture to help you visualise the setup.

View attachment 54303

 

[Debs]

This is the C-Tek batt to batt charger with the appropriate size cables and fuses. As Phil says, these amperages are not to be taken lightly, so if you're not sure, get some help and stay safe.

View attachment 54304

 

[Alf]

Have a look at this link Clive Mott is a long time motorcaravanner and a consultant for MMM

ALF

Clive`s

 

[sasquatch]

On my first van,a VW I had this engine andanother battery connected in parallel with a Hella switch between them,when on-site I switched the second battery off,which left for starting. This very basic setup worked before I discovered leisure batteries and split charging,it worked for me BUT ALWAYS USE THE CORRECT GUAGE OF WIRE AND FUSES.

 

[Veronica Walker]

Thank you all.

Thank you everyone for your information, don't worry I'm not doing it, I do have someone who knows what he is doing, just needed confirmation on how it is done and what exactly what spec was required, and you all have helped no-end with your information.
Special thanks to Wanderer015 for your link to the split kit, that was one of the queries we had, not sure what to buy, but with that it is all there almost. Also admin for your drawing, it will be useful, and Alf for you link to Clive, very useful.
Thanks again everyone, I shall let you know how we go.
Regards
Veronica :camper:

 

[trevskoda]

Thank you everyone for your information, don't worry I'm not doing it, I do have someone who knows what he is doing, just needed confirmation on how it is done and what exactly what spec was required, and you all have helped no-end with your information.
Special thanks to Wanderer015 for your link to the split kit, that was one of the queries we had, not sure what to buy, but with that it is all there almost. Also admin for your drawing, it will be useful, and Alf for you link to Clive, very useful.
Thanks again everyone, I shall let you know how we go.
Regards
Veronica :camper:

I have seen lots of jobs by so called experts which i have had to fix.
For a simple job either use a spit diode block or a relay about 200ah /cheep on ebay ,and battery cable fused if you like as hairy dog states/mind car batterys are not fused,but always take the output from les to a multy fuse box for wiring al units through.
The relay is shut when run from the signal alternator wire /engine running which should have a small fuse.

 

[maja07]

Split charge relay

Please also remember that it must be fused at both ends as there is power at both ends.

I draw you a picture to help you visualise the setup.

View attachment 54303

Hi folks, at great risk of being annoying......these setups....Phil has told me once !!
When on the move our van provides a trickle to leisure battery. If you put these above systems in place
does it mean that once vehicle battery charged the relay then sends higher current charge (via thicker cables) to leisure battery so it charges far quicker while on the move ? Sorry for being a pain LOL !!
Maja

 

[Veronica Walker]

Follow-up/

Hello everyone,

Thanks once again for all of your information and advice, I have now had the job done, by a professional in his own business. The job was done in a couple of hours and done very well. I bought a spliter kit as was suggested and my man said it had saved waisting a lot of time ordering it, and agreed it was the best thing to do. Even got a guarantee with it. So now I have running water and lighting, along with sockets to charge stuff on as I go.
Look out open road, here I come.........
Happy days everyone.
Veronica

 

[Roger]

I know this has been resolved, but thought I'd add my two bob's worth.

I have a 30 year old Westfalia that uses a really simple leisure battery recharging system, an 80amp relay/solenoid that is connected to the + vehicle battery and then onto the + leisure battery. When the engine is off the relay is open circuit (no power) so that the vehicle battery is isolated from the leisure batteries. The relay is opened/closed by using the circuit that turns off the dashboard alternator light, light off/engine running relay closed or engine off relay open. There is a 12V battery charger on the mains circuit.

Don't forget that your alternator has all the sensing ability to not overcharge batteries, well developed and reliable technology. The smart chargers are just doubling up the alternator's inbuilt regulators.

This works fine for most types of batteries, it wont work well for LiIon unless they have inbuilt charging. Does anyone have LiIon leisure batteries?

The expensive smart chargers do a couple of things (in theory) they will bring the vehicle battery to full charge before the leisure batteries and often have a mains connection which I'm not convinced could (one day) make the 12V system a melted mess. They will also compensate for the differences in voltage between old/new/different sized batteries which is handy if you have batteries of different sizes and ages or need a solar input.