Piggy-Backing Smart Chargers

If you leave your aux battery disconnected it should survive happily for 6 weeks without a charge, then use the smart charger as described on the main battery.

Leave the 2 batteries connected together in parallel (with the existing wiring or with jumper leads, or whatever) and connect the charger to either one of them.

I do this for the OKA house plus crank plus Margaret's shopping trolley crank for over 6 months at a time using the OKA's solar when parked in the shed with some polycarbonate sheeting to let some light in.

But, yes, they should be OK if left for 6 weeks if you simply disconnect the terminals to ensure that there are no loads.

Cheers,
Peter

Not wise. The charger is designed to adjust to a battery.

Do you have any kind of isolator between the batteries?

If current will readily flow between them and they're wired in parallel, then use one pair of clips: +ve to one battery +ve and -ve to the other battery -ve.

Gday Bill, I realise this is not a direct answer to your question but I bought a 10w Solar Cell from JayCar and a regulator to stop overcharging and found it works very well. I was originally going to leave my Holden on a trickle charger while I was away for 5 weeks but thought the Solar Cell a better and safer option, not connected to the mains power. I bought a 10W model because I can also use it on my Patrol which has two batteries in Parallel. The 5W model solar cell, also from JayCar does not need a regulator if you use on one battery. The 10W solar cell and regulator was under $100. I hope this helps. Regards, Michael.

If you're worried why don't you disconnect both batteries?

Bill since you have said you have a redarc system, I am presuming a VSR between the batteries, that means both are charged by the one source, ie alternator.
Therefore, simply connecting a charger with a daily timer for 20 min, plenty, will keep both charged.
Even a jumper across the terminals of the VSR will lock both together and the charger will supply to both. It won't matter if the voltage gets to VSR level because it will simply switch ON and OFF when the charger stops and batteries voltage drops to rest voltage.

You titled the piece, Piggy Backing Smart chargers, ie, two charge sources, that implies two chargers.
But what you have said is, Piggy Backing Batteries charged by one Smart Charger .

hi guys...i have a question ...i have 2 solar panels on the roof of my caravan correctly wired to charge 2 120 amp batteries under the caravan ...if i connect a third battery via the anderson plug on the van ...will it charge