dual battery

G'day Stuart, I am going down this road now. The general consensus seems to be (a) for a fridge, light, 12 volt camping accessories etc - Deep Cycle & (b) for winching or any other items that take huge amounts of current in short bursts etc - Starting Battery. I have been looking at all the smart controllers (and their costs) and decided I can buy a high amperage (345amp) marine switch and switch between the batteries manually (with the engine switched off to prevent spikes of course). This switch has Bat1, Bat2, and Bat1+2. How simple is that? Complete costs of set up- switch $40, extra battery cable- about $9 metre, additional battery terminals- about $20, hold down bracket and tray- $20 from wreckers, 75 amp/hour battery- about $140. Complete system for about $250.00. OK, it not as fancy as the electronic type controllers, and you do have to think about it, but (a) it is simple, ie, less to go wrong and if it does go wrong you can fix it easily and (b) another option and less than half the price! That bit got my attention! Hope this helps. Cheers!

Stuart, I looked at all aspects, have used deep cycle, start batteries and odessey batteries and have finally settled on 2 x 6 volt 220 amp/hr deep cycles. To charge these I have decided on a Arrid Twin charge from the 12 volt Shop in WA. This charger can put out up to 20 amps at a constant 14.7 volts, with an input voltage of 8-15 volts, I think that is correct, full details on there web site. http://www.12volt.com.au/ This allows the deep cycles to fully charge, unlike some systems. From what I have researched, it seems to be the "best". Not really expensive at $299.00. Have only used it locally up to now, but it performs well. The real test will come in July/August in the Kimberely. Hope this helps.

Hi Stuart
To run the fridge and light you require a deep cycle battery, one that allows for slow discharge, can go down to flat and be charged up again. The cca batteries are unsuitable and the marine are some where in between. The cca battery is use for the winch as well as starting, as it needs high discharge and fast recharge.
The next decision is separation of the batteries, I use a smart solenoid, means that I won't forget to switch it on and with many of the new systems in cars they won't even roll start if there is no charge in the battery.
Ray

Keep in mind that while a traditional deep cycle battery will last longer, it will not fully charge off the alternator and to get the best from it you should regularly charge it off a mains charger. I use a Arlec 10 amp (rms) charger to keep my 95 Ah deep cycle running happily.

For simplicity, 2 CCA batteries works well. Don't have one of each type, or, as Nigel suggests, the deep cycle will not charge. (mine died within 12 mths!) Liemack Fridges recommends having both batteries paralleled at all times, and an adjustable low voltage cut-out on the fridge. The cut-out prevents the batteries from "deep cycling", so there is no need for the extra expense. The flash battery isolators are great while working, but I know a few bods who've ripped them out after failure.