dual batteries

I don't know where you are Ashy but if in Sydney I would recommend a caravan accessories shop in Carlton. They do this sort of thin all the time, have been doing it for a long time and are getting it right.

I am not an expert on these things but I run a battery on my camper trailer and it is a very simple install, and it works. My trailer battery is connected in parallel with the second battery in the car. All I have done is run a heavy cable from the + terminal on the car battery to the back of the car where it connects to the trailer battery when I plug it in. There are a number of plugs you can use for this, most people use an Anderson plug but I have an 11 pin flat plug which does the trailer lights and the battery in one go.

It is important to keep both batteries in good condition and to this end I have a small solar panel connected to the trailer at all times.

This works for me but my second battery in the car is managed by an isolator between it and the main battery. You may need to put this type of device between the car and the ct if you don't have a dual battery system in already.

Hope this helps but I am sure you will get a more detailed response from someone here soon.

Duncs

Hi. I have done that but I do not have a second battery in my car, just the caravan.
The caravan battery is stored in a ventilated box on the draw bar of the caravan. I am using a Trojan DSB but an AGM would be more suitable.
I am using 18m3 cable from my main battery via a 175amp Anderson plug to the battery on the caravan. In the engine bay of the car is a solenoid switch on the positive cable which is only closed when the ignition switch is in the "ON" position.
I have installed two 80amp fuses. The first fuse is in the engine bay and has been installed in the positive auxiliary cable adjacent to the main battery. The second is in the positive cable in the ventilated box on the caravan adjacent to the auxiliary battery.
One advantage of having your second battery in your caravan and not in your car is that you can uncouple your car and caravan and still have 12v power in your caravan.

Ashy,
As this is an independent Auxiliary battery used in your CT instead of your car you have to use a "battery isolator" and a decent fuse installed near the existing Cranking battery and "thick" battery cable back to an Anderson plug at the back bumper to eliminate the second battery draining the existing Cranking battery when parked.
I realise you only want to run 'lights' but some day you may decide to connect a decent AGM battery and a fridge to the same battery cable !!!

The thick battery cable avoids battery voltage loss and yes will cost you about $20 more than 'thin' inefficient cable, the major benefit is you will not damage your battery by having it undercharged and sulphating.

Hi Ashy,
I have just hooked up a similar system but I have made the second battery portable in the back of my trayback for a fridge, lights etc.
I ran B&S 8 cable via a 50Amp curcuit breaker near the main battery (positive) then through a 100amp Redark battery isolator then terminated the cables (red/black) behind the cab and trayback via a 50 amp anderson plug.
my spare (second) battery also has twin 50 amp anderson plugs , one input and one output . this way I can use either the main battery or the auxillery . The part that impresses me is that the Redark isolates the main battery at approx. 12.4volts so you will not discharge the starter battery.

Hi Ashy

I have just written a new artice on this.

Articles

Click on the Caravan Charge Link.

Regards

Derek.