Leisure battery charging from car

[qhrider]

I just bought a horse trailer with living. I had been told that the leisure battery would charge from the car while driving (I had put an extra plug on my car for this) but when I drove for 5 hours with fridge on, I had no battery charge left, so the car did not charge the battery or run the fridge! The electrics work with the car running, but does not charge the battery. Do I need anything extra for having the car charge the battery? Someone mentioned I might need a charging unit installed, but why was this not mentioned to me at purchase? HELP, this is a second hand vehicle so have no where to turn. Battery works great when charged and fridge can be on the gas once stopped but not while driving.

 

[caspar]

This does not have to be expensive at all - I did mine for about £6 or £7. All you need is a spotlight relay from a motor factors and a couple of fuse holders to wire in line. Very easy to do and can be wired diect to alternator or ignition (something that switches it off automatically when you turn the engine off so you don't frain your vehicle battery), or you can wire it to a manual switch so you can switch it on and off as you wish.

I'm pretty sure I've got a spare relay designed properly for the job somewhere which you're welcome to if I can find it. pm me or e-mail at davidlindley@sky.com with a phone number and I'll get in touch! Just remind me who you are in an e-mail or you'll end up in my spam. Maybe subject Leisure Battery do not delete or something similar as a memory jog for me. It would save you about £15-20 that I paid for it and it's no use here doing nothing!

 

[Deleted member 3011]

One of the biggest problems with charging the leisure battery from the car alternator is high voltage drop over skinny wiring.
Ideally there should be heavy wiring run directly from the engine compartment to a separate andersen plug at the back of the car and then heavy wiring from there to the leisure battery and the fridge.
As previous poster said, you need to have a voltage sensitive relay or similar system to isolate the two systems when the vehicle is stopped. Another relay, sometimes motion activated, will isolate the fridge when stopped so the fridge drains neither battery.

As for your particular problem - only way is to physically check any wiring in the trailer and see just how the battery is supposed to be connected to the car alternator. Perhaps the wiring in the existing plug has a different pin connection to the socket on the car, perhaps a fuse has blown or there is a manual switch in the circuit somewhere. A cheap digital multimeter or test lamp will also assist in fault-finding

BTW - running a battery dead flat once isn't good for the battery but not too much harm is done provided the battery is recharged ASAP. Leaving it flat for several days may well be terminal.

 

[caspar]

One of the biggest problems with charging the leisure battery from the car alternator is high voltage drop over skinny wiring.
.

Yep! For goodness sake use the correct wiring and fuses otherwise you could well have a fire on your hands!