Triple battery installation

Dave.
Having 2 deap cycle batteries in parallel is ok for charging purposes. The problem only arises when you want to discharge them seperately. The simple solution for you is to use a relay to connect the 2 in parralel while the ignition is on. Eric.

Hi Dave,
I spent a bit and got a Rotronics system.
I caters for a main cranking Battery and an in vehicle aux battery which can be a deep cycle or cranking battery, plus a campervan battery probably deep cycle.

It work because it isolates and charges each battery in turn therefore having different types of battery in the vehicle is not an issue.

At present I have 2 cranking type batteries (Exide Extremes) in the car. I will eventually install a deep cycle in the campertrailer.

Hope this is helpful to you

Dave,
Why not use the same brand, size etc, Deep Cycle battery as you are presently using in the camper?
I presently use two Deep Cycle batteries wired in parallel and seperated from the Cranking battery by a DBE 150S electronic isolator without problems.

With two Deep Cycle batteries of totally different capacities I would be wiring them in parallel as normal for charging, however I would then install a two way isolation switch to draw power from either battery at a time, not both, as when one battery is very low in power it will draw from the higher charged one, assuming the two DC batteries are of totally different power capacities.
As I say two identical DC batteries is the easy way to go (if possible) and remember to use large diameter cable to connect the two DC batteries to avoid voltage drop.
hope this assists you->
link text

Hi Dave.
As the batteries are the same type, and you are going to connect them in parallel, then there is no reason to do anything more than just couple the batteries permanently together. Even if the batteries have different AH capacity, once they are connected together, they will then act as one battery with an AH capacity that is equal the the combined AH of both batteries EG. if you have a 50 AH battery and a 100 AH battery connected in parallel, you affectively have one 150 AH battery or a bank of batteries that gives you a supply of 150 AH.
The only time you can not connect the batteries together if they are not the same AH rating is if you want to connect them in series to give your self a 24 volt supply for some reason, such as welding. In this situation they must be the same capacity if you are going to use them this way for any length of time.
One word of warning. Some of the Piranha products have a habit of leaking back across the unit from the auxiliary battery to the cranking battery if the cranking battery voltage falls bellow the auxiliary battery voltage. Just keep an eye on that one.
Regards.

The guys at Rotronics were very helpful when I called about a question I had regarding the system in my car. They have a website and it has plenty of advise too. Can't remember the URL but type Rotronics into a search and it should ahow up. They have a 1800 number listed on the site and if you call them I am sure they will be able to help.

I don't believe they are cheap but having been stuck with 2 dead batteries and a fried isolater I would rather pay the bucks and get something that is reliable.

Duncs

Dave,
Try the very helpful people at Redarc in Adelaide.
www.redarc.com.au
(08) 8186 5633
Their gear is first class and Aussie made.
If you have a truck, most of their equipment is available in 24V as well as 12V.
Trev

Thanks for the replies people. The main problem is the batterys are different types. This is due to there not being much room under the bonnet to fit a large battery. The One I have to go into the car is a 50 AH dry cell low res unit and the one I run on the camper is a 150Ah wet cell to allow for the much heavier loads when using the camper. I know there are equlisers for batterys in series but am trying to find out if there is a unit for parellel connected batterys.

Hi Dave,

Briefly went down this path for slightly differnt reasons. Budget price for the Rotronics was K$2 but that was because making the wiring neat and tidy and a professional look is very labour intensive. But they do have the gear.
My problem was that connecting the caravan battery and the auxilliary battery in parallel meant that when stopped for short periods both batteries were connect to the same load and therefore settled at the same voltage level. The vehicle aux.battery feeds my car engel, lap top, GPS etc and also feeds the 3 way fridge 12 V when we are on the move. So far I've left the charging diode in place in the van even though I loose about .6V. At least I know the van batterry is as fully charged (pobably only 80% though) when we stop for the night.
I think I've got to go solar, generator, or Christie battery charger to top up my batteries when mains is not avilable.

Regards,

Rosscoe