separation of dual battery banks

Submitted: Thursday, Jan 06, 2011 at 21:22
ThreadID: 83476 Views:2854 Replies:3 FollowUps:1
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I am trying to sort out my battery system in my campervan. It has a side compartment for the battery (added as part of conversion). I plan on placing a starter battery in the engine cavity and putting a agm deep cycle in the side compartment.
My issue is can i connect up two different battery types via a solenoid isolator, so they both charge off the alternator but do not work as a bank, or do I require something further?

thanks for any help anyone can offer

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Reply By: Member - Christopher P (NSW) - Thursday, Jan 06, 2011 at 21:41

Thursday, Jan 06, 2011 at 21:41
G'day Trev, it would be better with a smart redarc, because you can put a solenoid in, but it would.nt charge the AGM to full capacity. It is a bit more expensive but you won't/ shouldn't have that many problems. Just pulling up all the dual battery setups on this forum for you to read!!!!

Dual battery

The other good guys to talk to are Derek (I think ) from ABR, And a couple of others, they are a good source of information.
AnswerID: 440902

Reply By: Mick O - Friday, Jan 07, 2011 at 07:23

Friday, Jan 07, 2011 at 07:23

have a look at the Redarc BCDC1220 charger. It's an isolator and DCDC charger. From the product decription;

"The Smart Start® BCDC1220 features multi stage
charging profiles specific to the chemistry of the battery
under charge, allowing you to charge an auxiliary
battery that is of different chemical characteristics to
that of the source battery. The unit will act as a dual
battery isolator and protect the start battery, should the
voltage get too low."

BCDC 1220 Product Specs

I've been using one to charge a hybrid deep cycle as my vehicle auxillary and being a DCDC charger, it ensures the appropriate levels of charge required by AGM batteries.

From the Redarc newsletter, they are releasing the next model this February which includes an MPPT solar controller. Even better functionality in my book. Means you can plug your solar cells straight to the dual battery setup for charging your AGM.

Heres a link to a write up I did on the Redarc products I've been using

Product Review - Redarc

Cheers Mick
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trip would doubtless be attended with much hardship.''
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AnswerID: 440926

Reply By: trainslux - Friday, Jan 07, 2011 at 13:04

Friday, Jan 07, 2011 at 13:04
Basic answer is yes you can.
Ensure you are running the thickest cable you can from your starter battery to whatever solenoid you are running and then back to the trailer.
Anderson plugs are the choice of most to connect at the coupling.
Voltage drop is your enemy running wire from front of vehicle to trailer etc.

However, if you drain your agm down to say 50%, and only drive for an hr the next day, you may well not top up your agm for that short trip.

If you spend 5 + hrs on the road, then there is a good chance you have been able to top up your agm and starter to 90%.

The last few % of top up usually take a higher voltage than your car charging system can offer, say 14.5, car might peter out once operating temps are obtained at 13.8.
In saying that, given enough time, full charge can be obtained by 13.8v ish output

So basically, fine for travelling, when you stop at a park, or have access to 240v you can then charge it up the last bit overnight with your 240v battery charger etc, or if you have solar, use them.

The 12v 12v chargers are a good investment if you want that full charge, mount them next to your agm trailer batteries.

Whilst the alternator can put out higher amps to begin with, the 12v 12v charger comes into its own when/ if you suffer voltage drop, or want that last bit put into your batteries, especially if your alternator is charging the crank batt at 13.8ish, and you want more into your agm's.

This is the readers digest version.
Any solenoid will do, a manual on off will work just as a redarc smart one will.

I have both on my vehicle with 3 batteries, and it works well.
some solenoids have better contacts inside than others, thus offer better current flow over a longer service life than others, but basically then all do the same thing, isolate, or connect the 2nd battery to the cars charging system.

hope that helps


AnswerID: 440966

Follow Up By: Mandrakemuffley - Sunday, Jan 09, 2011 at 21:03

Sunday, Jan 09, 2011 at 21:03
Thanks all! i very much appreciate the assistance from everyone. i have been trying to get my head around this stuff for weeks now!
Can't wait to get my baby up and firing!

FollowupID: 713314

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