Help electrical wiring for leisure battery and towing

[Odd-no-more]

Any electrical wizards? I need help. I am getting a van to convert to a day van, I want to have a 12 volt compressor fridge and a leisure battery to run it, but I also want to tow a caravan and have a 12 volt supply for the fridge when towing. I don't need both at the same time so is it best just to put in a simple 2 throw switch which I may forget to change over, or can I get a relay to operate when I connect the caravan? and it it is possible how would I wire it?

Thanks in advance
John

 

[pappajohn]

Just turn off the compressor fridge when not needed. If you forget it's not the end of the world.

 

[Odd-no-more]

It's not the fridge, it is running the 12 volts to the caravan when towing and disconnecting the feed to the on board leisure battery, as I doubt the alternator could charge all 3 batteries at once

 

[SandraL]

It's not the fridge, it is running the 12 volts to the caravan when towing and disconnecting the feed to the on board leisure battery, as I doubt the alternator could charge all 3 batteries at once

Many vans charge 3 batteries at once, starter and 2 leisure as in my van. Often starter batt is not low but leisure can be. I think alternator will be ok .

 

[dunnah01]

A 2 pole relay triggered by pin 2 on the 12S socket to isolate the van supply and allow supply to 12S pin 6 should work.

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[Snowbird]

My fifth wheel tow truck alternator charges the engine battery plus 2 x leisure batteries on the fiver, plus a separate inverter battery with no problems. An auto electrician wired everything up for me, so unfortunately I cannot help in how it was done.

 

[chaser]

Yeah my Renault ex ambulance charges van battery and two habitation, 330 amps altogether, the 100 w solar panel does all three as well.

 

[cmcardle75]

Don't worry about it. The alternator will only give out as much power as it wants. It'll just reduce voltage if there are too many batteries to charge. Compressor fridge is only a few amps. It won't event notice that.