Member - andrew B (Kununurra) replied:

Gday Arkay

I think its a matter of different strokes for different folks (and system requirements) I have a simple solenoid for under bonnet. I like it as I have both betteries in parallell while winching etc. Smart solenoids generally don't allow this. A downfall is it may hide a weak starting battery, as they are in paralell when the ignition is turned on, so in the case of a stuffed start battery the aux will 'jump start' the car.

Then you go bush, run the aux down with the fridge, and then in the morning I may not be able to start the car.

Basically, If your wireing is heavy enough to handle the loads you place on it, and you have appropriate fuses etc you won't start a fire, but if you ask too much of a system which is not set up correctly you will have problems.

Best thing to do is research what others have, weigh up the pro's and cons of peoples systems, then pick the one that suits your needs and budget the best.

Good luck

Cheers Andrew

Member - Brian (Gold Coast) replied:

I agree, in that the dual battery ssytem should be as simple as possible. I used solenoids for the last three years, have now graduated to a Redarc, but only because of their reputation for being reliable. So far so good, as long as I don't have to change it every 8 or 9 months like I did with the solenoids.
But personally, I can't see the point in anything more "tech" than that.

Member - Mike DID replied:

It doesn't even have to be as complicated as a Solenoid - I spent three months outback travelling using just a manual Isolating Switch between Main and Auxiliary Battery. When you stopped to camp, you turned to the switch off. When you were leaving camp, you turned the switch on.

Reliability through simplicity - providing you aren't forgetful !

Derek from Affordable Batteries & Radiators replied:

Hi Arkay,

The main reason for these components is to obtain the best charge rate and reliability with everything being automatic.

You have a battery in your van. There are still some vans out there with no battery. Why ? People like to have things that work and have luxury when they are away from home. Having a good 12V power supply and charge system makes this easy.

Read my Battery Article

Regards Derek.

longJohn replied:

I had a old rocky i used to drive to fraser, and with a fridge, second battery system, just had a standard 40A relay connecting the second battery to the alternator. It was wired up so ignition on, relay on. Ignition off, relay off, both batteries seperated. Had another relay with NC contacts wired up to the starter motor start signal (solenoid) , so when it was cranking, the second battery was isolated so cranking current didnt flow from the second battery. Had many critisise my system but it worked flawlessly and I still use that battery in my new 4wd.

Heres a story that happened to a mate, he had all the fancy gear, intellegent battery system (what does it do other than disconnect during initial charging???) and went to moreton island. As soon as the tyres hit the sand coming off the barge, his radio stopped. Then they lost a bolt out of the brakes, spent hours looking for it, got a new one arranged at the local shop and went to the campsite, and then the fridge stopped because the second battery was flat. Found that the alternator had not charged since the barge and had a blown regulator. They pulled it apart and soldered a wire direclty to the armature and connected it to a bulb to earth to give the alt some exitation so it would charge. Found that while driving, with the bulb hooked up, it outputted 16volts. with it disconnected of course it was off. So they spent the next week with it sometimes connected sometimes not to give everything a charge. Switching on all the accessories and spotties to use some of the voltage up helped things a bit, but they were very glad to get a new regulator finally to get back to normal!
Meanwhile they found a bolt had fallen out of the brakes on the other side and they had to go back to the shop for another bolt :~!!