12 Volt caravan and 24 volt vehicle

Quite right Brett C.
Common problem, pain in the butt. The ony other option is a seperate 12V system and battery in the back, or change everything to 24V.
Don't be tempted to 'peel' 12V off from 1 battery in your 24V system. It will kill both batteries quick.

Cheers,
Peter.

Well only if you don't do it properly Peter.

Redarc make all the gear you need. www.redarc.com.au

- Voltage reducers for your caravan supply if you choose to go that way.
- Charge equalisers so you CAN safely pull 12v from the high pole of the low battery, or the low pole of the high battery.
- Electric brake controllers. 12v and 24v

I know this has been well covered before in the forum. but basically the problem is not draining one battery or the other in your 12v setup, it is recharging them. When your alternator punches in 28v and one battery is at 12.6v and the other at 11.6v, the charge does NOT go into the 11.6v battery and bring it up to the other battery. It overcharges one and undercharges the other, eventually crashing both.

I have a very successful setup on my 24v import landcruiser where I draw all my 12v from the -ve pole of the high battery. I have installed a 20A Redarc charge equaliser so this allows 20A of extra current to go into the low battery and charge it up until it is balanced with the high battery.

When travelling, an aux battery is also connected to this same circuit and it is recharged very satisfactorily and all batteries balanced as needed. It is protected from overdischarge by a gizmo.

If you were to try to have several batteries as 12v aux, or in the caravan, I would suggest you looked at a higher capacity charge equaliser.

Another option I have contemplated is to charge 2x12v batteries in series in my trailer with 24v current, then when stopped disconnect the charge circuit via DPDT relays and drain them equally by putting them into parallel so producing 12v. I 'think' I have figured the switchery on the relays, just not got around to building it yet.

The other option you have for the lights on the van is to upgrade them to 24v stop tail and turn lamps. You will still need to supply 12v to the van for you acc. Don't know about brake controller, Redarc will have a solution.

Good luck, it's kinda fun after a while. Gives you something to think about driving along :-)

Tim

Yes that is one option.

A disadvantage of these is that you need to buy one to suit all your current draw. This might not be a problem, and also you can mount them down the back of the vehicle away from your batteries, or even in the caravan, and have the more efficient 24v current doing the longer run.

An advantage of a charge equaliser is that it doesn't matter what short term current you draw from your 12v supply, over time it will be adequately replenished by the correctly sized equaliser. A disadvantage of them is that they need to be close to the batteries, and essentially in the engine bay.

Tim

Just looking at the size of the heatsink versus the output current of this unit, I'd say this is a simple analogue voltage regulator; ie, it dissipates the excess voltage as heat. OK for low current draw, but pretty wasteful otherwise. And they're very cheap to make.
Look for a switching regulator as listed above if you're going down this path and allow enough capacity to cope with the max load and the starting current of the fridge.
Gerry