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Old 11-14-2018, 03:20 PM
lj_mastercraft lj_mastercraft is offline
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Battery maintainer wiring

I've got a battery maintainer that can easily handle both batteries, but for the last year and a half I've just been plugging it on to one battery at a time (and every weekend I alternate to the other). Typically the boat keeps both charged, so it's just to maintain.

I have two methods:

Method 1 (see first image below) - Get a dual bank charger, and connect each charging bank to a battery. This means that the two 'negatives' will technically be connected to each other. Although not shown in the diagram, there is actually another box that sits next to the Perko switch that connects to the alternator, and then a lead to each battery. I believe that allows the alternator to charge both batteries regardless which is selected on the Perko? Want to be sure this is a safe method considering that.

Method 2 (see second image below) - Use my single bank charger, which has enough juice to charge both batteries, but connect both batteries in parallel (still disconnected at the perko), so the charger sees one big battery bank

Again - want to be sure of the safety factor. To my understanding either one would work, but I do want to be sure i'm going about this the right way.

Important to note that it's very seldom (if ever) that i'll put the boat up with one bank completely depleted. Usually they're coming back at 50% or higher on each bank.
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Old 11-14-2018, 05:22 PM
waterlogged882 waterlogged882 is offline
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I prefer a single bank for each battery (separate units for me that sit on a shelf and plug into pig tails to the batteries). I just don't prefer the onboard installation.

Like you say, either will work but from the choice of those two examples, I'd go with dual banks.

Your call.

.
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Old 11-14-2018, 05:28 PM
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lakedrum03 lakedrum03 is offline
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Quote:
Originally Posted by waterlogged882 View Post
I prefer a single bank for each battery (separate units for me that sit on a shelf and plug into pig tails to the batteries). I just don't prefer the onboard installation.

Like you say, either will work but from the choice of those two examples, I'd go with dual banks.

Your call.

.
+1 on what WL says.
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Old 11-14-2018, 06:25 PM
MLA MLA is offline
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Most battery charger manufactures discourage modifying the cables, so splicing a single bank charger off to two, is not suggested. Leaving the switch to ON, so the charger connected to one, chargers both, I do not suggest.

Get a good 2-bank multi-stage smart smart charger or a 2nd small single bank and just plug both into your extension cable.
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Old 11-15-2018, 08:38 PM
lj_mastercraft lj_mastercraft is offline
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The first image IS a dual bank maintainer - in that it has two separate chargers (with two + and - leads).

My concern with that is that essentially the two negative leads will be connected together (in that the negatives of both batteries are shared).

Also, besides the Perko switch, both batteries have their + cables going to a box that connects to the alternator. My understanding was that the alternator can charge both batteries regardless which selection the perko is on
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Old 11-15-2018, 09:44 PM
MLA MLA is offline
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That ground link between the banks, has no impact on the battery charger. However, it HAS to be there, in order for the alternator to charge both banks. Otherwise, the one bank is not technically part of the electrical loop.

I would not insert an ACR/VSR into the on-board charger discussion. Neither has anything to do with the other. Just my opinion.
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Old 11-16-2018, 12:34 AM
lj_mastercraft lj_mastercraft is offline
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Yeah I understand why the ground link has to be there, and I'm not disputing that, but essentially the negatives on the battery chargers would be connected to each other and to the ground, but the positives would connected to each battery

The ACR/VSR (if that's what it is) should absolutely be included in an on-board charger discussion! The reason is because it's designed to allow the charging of batteries to occur regardless how they are isolated at the Perko. If you connect two battery chargers to each other (positive to positive, negative to negative) and the plug them both in, I've got to believe that's not a good thing. That's essentially what you would potentially be doing. In fact the discussion is ALL ABOUT what the ACR/VSR role is in this
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Old 11-16-2018, 09:05 AM
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Again, it creates no issue to have the charger's negative cables linked through the dual bank ground link. Being a dual bank charger, the positive circuits will be independent and isolated internally on the charger.

As to the a combiner, IF the combiner becomes active during shore charging, though less then ideal, the charger will still charge both banks. If the boat has the Dual Circuit Plus type switch, and it wired in the most ideal manor, then any type of isolator/combiner can be taken out of the shore charging loop, when the switch is off.
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Old 11-16-2018, 12:51 PM
lj_mastercraft lj_mastercraft is offline
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OK so if the combiner becomes active, then the two charger banks will both be connected to each other and two both batteries in a parallel load... so that won't cause any issues?

if that's the case, then my fears go away
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Old 11-16-2018, 01:40 PM
MLA MLA is offline
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It should not cause a negative, as in let the magic smoke out. Only real downside is that the dual bank charge is less effective in recharging each bank individually.
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