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jbeliera

Boise Idaho

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Posted: 02/10/18 10:06am Link  |  Quote  |  Print  |  Notify Moderator

Here is a technical question. Let's say you want to charge your house batteries on your RV quicker. If you have two 12 volt batteries in your battery bank would you charge that battery bank quicker if you put two 25 amp battery charges on at the same time. Would that be possible to increase charging amps and less charge time or would it fry your batteries


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2oldman

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Posted: 02/10/18 10:09am Link  |  Quote  |  Print  |  Notify Moderator

That's fine.. with caveats. Two chargers may not work well together, meaning one may charge at a higher voltage and fool the other into thinking the batteries are charged. In that case, simply charge them separately.

ScottG

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Posted: 02/10/18 10:14am Link  |  Quote  |  Print  |  Notify Moderator

Works best if neither one is a "Smart" charger.


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theoldwizard1

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Posted: 02/10/18 10:19am Link  |  Quote  |  Print  |  Notify Moderator

If they are both smart chargers, separate the batteries and charge them independently.

2oldman

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Posted: 02/10/18 10:20am Link  |  Quote  |  Print  |  Notify Moderator

theoldwizard1 wrote:

If they are both smart chargers, separate the batteries and charge them independently.
You don't really have to separate them.. do you?

BFL13

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Posted: 02/10/18 10:28am Link  |  Quote  |  Print  |  Notify Moderator

Another limitation is your generator. Each charger draws some of its VA, so you need enough total VA to run all the chargers.

It is better to put the chargers' clamps across both batteries that are in parallel ( two pos clamps on the same post and two neg clamps on the the other battery's neg post via Trimetric shunt). Or put one charger on each battery. (But then the total amps won't show on your Trimetric)

Not so good to have both chargers on one of the batteries. Then that battery gets more of the recharge. If you can only get at the front battery posts with clamps, then you can reverse one battery and criss- cross the parallel links so that the two posts in front are the pos from one and the neg from the other, so now you can clamp on with them balanced.

If one charger has a slightly lower voltage than the other, start that one first and get it running, then turn on the other charger.


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Chum lee

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Posted: 02/10/18 10:34am Link  |  Quote  |  Print  |  Notify Moderator

jbeliera wrote:

Here is a technical question. Let's say you want to charge your house batteries on your RV quicker. If you have two 12 volt batteries in your battery bank would you charge that battery bank quicker if you put two 25 amp battery charges on at the same time. Would that be possible to increase charging amps and less charge time or would it fry your batteries


I use a separate 10 amp charger to charge my house batteries all the time without issue on my class A. The motor homes load center has a charger that will also charge the house batteries (2 - 6V deep cycle wet cell) when connected to 120V but it does a lousy job. In your application you need to know the charge voltage of both chargers. They may be substantially different if the chargers were made by different manufacturers. Generally (not always) the charger with the highest charge voltage will do most of the charging because it will tell the other charger to "back off" because it thinks that the batteries are all ready charged more than they are.

In short, just because you use 2 - 25 amp chargers doesn't guarantee you'll be charging at 50 amps initially. In some cases connecting two 25 amp chargers may reduce the charge voltage and initial charge amperage well below 25 amps.


Chum lee

ScottG

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Posted: 02/10/18 11:00am Link  |  Quote  |  Print  |  Notify Moderator

2oldman wrote:

theoldwizard1 wrote:

If they are both smart chargers, separate the batteries and charge them independently.
You don't really have to separate them.. do you?


For best results - yes.

2oldman

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Posted: 02/10/18 11:26am Link  |  Quote  |  Print  |  Notify Moderator

OK, yes, parallel batteries might do better separated. Series, no.

ScottG

Bothell Wa.

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Posted: 02/10/18 11:55am Link  |  Quote  |  Print  |  Notify Moderator

2oldman wrote:

OK, yes, parallel batteries might do better separated. Series, no.


Remember, the discussion is about using two chargers. Trying to use two smart chargers for either parallel or series batteries never works well if the two chargers are in parallel.

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