Question to Derek

Why not contact him direct, for a speedier answer Link

Just to get up DIO's nose... I'll answer what I know.

You will be charging both batteries when they are connected.

The charger is just putting out (say) 12A and this will charge both batteries at relative rates depending on their ability to accept charge.

I'd guess the switch on the charger is to provide a higher Amp output (say 6A for 100 Ah) which is rather arbitrary anyway. Look at the documentation for the charger.

Generally speaking, however, there are a few traps to charging them together if they are not being used together - the smart charger switches to trickle mode based on voltage, for instance, and if one of those batteries comes up faster, the other battery may be under-done.

Thanks for that Vivid, I posted to Derek because he generally answers so that you can understand but you have given me what I wanted. No literature on my charger so can't consult it and I thought there may ba a few others interested in the answer.

Cheers Rod

Rodney,
I know your question is well answered.
I run the same as you under the bonnet - 2 identical batteries connected by a marine switch.Mine stay connected all the time - so they start together, charge together, and for one night stays they run the fridge together (longer stays I isolate them). I like it because its simple, and each battery is required to do less work. Downside is that if one battery drops a cell, the other one will get pulled down.
When hooking them up to a 240V charger, I hook the charger into one of my power outlets in the cab.
I do also run a 3rd battery (AGM) in the canopy, but that is isolated with a fancy isolator.

Cheers
phil

Thanks Phil and Derek for your answers .
The battery charger is a PowerTek Plus 4 stage charger (purchased from Jaycar) and gives the abilty to select 25 to 100 or 100 to 200 AH and works very well.

Like Phil I also have the CT with a smaller battery that charges via Anderson Plug from the Main and have been operating this setup for about 2 1/2 years with no problems.

I run two identical Batteries in the Cruiser with a H/D isolator and only run the engel off the Aux overnight or long stays.

So far I have never had a flat battery and I keep the Multi meter handy and use the Honda if the voltage drops on the Aux.

The alternator seems to cope with the 3 batteries OK.

Cheers