Dual Battery Systems

Depends on what vehicle it is going in, what you expect it to do, How Electircally minded you are and how much you want to "automate" or control the system.

If in a non EFI vehicle then there are plenty, including myself who swear by the old solenoid type system. No good on a computer controlled vehicle or one which will be running equipment sensitive to spike's.

You simply wire the relay between the positive terminals of each battery then depending on how you want it to charge/isolate wire in the relay activation. Eg for manual you could run it through a switch in the dash. The power could be from a source that requires the ignition in the "run" position so at least when you turn the vehicle completely off it is isolated even if you forget to turn the swiotch off. Otherwise use a source such as oil pressure sender through a relay so that unless the engine has oil pressure (Eg running) the batteries are isolated.

Simpler again is a marine switch which relies on you selecting which battery can be charged or isolated, however if you forget to turn it off you could end up with two dead batteries.

Then you can move on to "smart soleniods" most of which are suitable for vehicles with computer management. Available from sprint and the likes for around $90-$150 depending on brand etc.

Feel free to PM me if you want more specifics.

IMHO spend the money on getting the biggest deep cycle you can afford (And fit). The charging system is no good if the battery is not capable of running the fridge for the time the vehicle is not running.

Hi mate,

You dont need to go to anything extreme for a 2 battery setup dont bother wasting good money on a 700 pirahna setup or the like. I fit 2 battery systems on a very regular basis and have found the best system to use is the redarc automated solenoid
it is safe to use on modern vehicles as prove I even have it fitted to my efi diesel in my 79 series cruiser and have never had a problem just make sure you use decent quality cabling to run from you're second battery to the controller I would recomend 2 B&S but you can go slightly smaller. I think the part number for the solenoid is s12 . I have fitted and sold at least 50 of these units since they came onto the market or atleast when they started getting widely used and have not seen one fail in any situation. In my vehicle it gets abused often in deep water crossings. I also have a trojan 115 amp/hr battery to run my fridge and get around 2-3 days out of my 60 litre waeco I hope this helps if you would like any more info feel free to email me

Alvey,

I won't promote any individual brand of Solonoid or Isolator.
I am not a reseller, or in marketing, or manufacturing of these products in any way.
I am simply a "knowledgeable user" with an electrical background.

The more expensive brands of isolators/controllers will give you the best "Bang for Buck" IMO and are backed by an Australian wide service and warranty.
That is why they are more expensive. But, compare the top brands and you will see they are all similar in price.

You said it yourself in your opening comments, "you get what you pay for"

So the choice is, buy cheaper and take the risk, or buy smarter and have piece of mind.