Piggy-Backing Smart Chargers

Submitted: Friday, Aug 03, 2018 at 15:54
ThreadID: 137077 Views:873 Replies:7 FollowUps:5
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HI all,
I am going away and will be leaving my Prado silent for about six weeks. I was going to setup my smart charger with two (2) alligator clip sets, feeding both the batteries.
Then setup a timer to turn the charger on one day a week for a few hours, to maintain the charge in both batteries.

Can a smart charger be used like this?

Thanks

bill
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Reply By: qldcamper - Friday, Aug 03, 2018 at 16:20

Friday, Aug 03, 2018 at 16:20
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.
AnswerID: 620478

Reply By: Peter_n_Margaret - Friday, Aug 03, 2018 at 16:47

Friday, Aug 03, 2018 at 16:47
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
AnswerID: 620479

Reply By: Sigmund - Saturday, Aug 04, 2018 at 12:53

Saturday, Aug 04, 2018 at 12:53
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.
AnswerID: 620500

Follow Up By: Member - bbuzz (NSW) - Saturday, Aug 04, 2018 at 12:59

Saturday, Aug 04, 2018 at 12:59
Hi,
I have a Redarc system (not sure of the model) to manage both batteries.

I guess the safe thing is to disconnect the spare and just charge the cranker.

Thanks

bill
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FollowupID: 892954

Reply By: Michael ( Moss Vale NSW) - Saturday, Aug 04, 2018 at 14:22

Saturday, Aug 04, 2018 at 14:22
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.
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AnswerID: 620501

Follow Up By: Member - bbuzz (NSW) - Saturday, Aug 04, 2018 at 17:15

Saturday, Aug 04, 2018 at 17:15
Thanks Michael,
I have that system on my boat batteries and it works a treat.
Just didn't want to have solar cells lying around when I am not using them.

bill

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FollowupID: 892963

Reply By: Member - peter_mcc - Saturday, Aug 04, 2018 at 15:18

Saturday, Aug 04, 2018 at 15:18
If you're worried why don't you disconnect both batteries?
AnswerID: 620503

Follow Up By: Member - bbuzz (NSW) - Saturday, Aug 04, 2018 at 17:14

Saturday, Aug 04, 2018 at 17:14
I was concerned that the batteries would discharge too much.
Not sure even now that they may do this without a trickle every now and then.

bill
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FollowupID: 892962

Reply By: RMD - Saturday, Aug 04, 2018 at 17:28

Saturday, Aug 04, 2018 at 17:28
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 .
AnswerID: 620505

Follow Up By: Member - bbuzz (NSW) - Saturday, Aug 04, 2018 at 17:57

Saturday, Aug 04, 2018 at 17:57
Sorry. Not sure how to caption it.

But yes; one charger and two batteries.

That sounds what I want. Good to know 20 mins will do the trick.

Thanks a bunch!

bill
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FollowupID: 892966

Reply By: Wayne G9 - Tuesday, Aug 07, 2018 at 18:53

Tuesday, Aug 07, 2018 at 18:53
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
AnswerID: 620580

Follow Up By: qldcamper - Thursday, Aug 09, 2018 at 15:39

Thursday, Aug 09, 2018 at 15:39
yes, many variables on compatability and stuff that some may want to make like is super critical but the short answer is yes if it is a similar type of battery and the anderson plug is wired direct to the vans battery bank.
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FollowupID: 893076

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