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Size of battery charger (how many banks)

Old 11-18-2016, 05:54 AM
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Default Size of battery charger (how many banks)

Let's say you have 4 batteries (one for each motor) and two batteries wired together for the house.

Do you A) get a 3 bank battery charger
Or, B) get a 4 bank battery charger

Remember 2 house batteries are tied together. If you charge one, you charge both.

What's the *proper* way to handle this?
Old 11-18-2016, 06:29 AM
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Probably depends on the charger but I use one bank for each battery. That's how the instructions showed them set up.
In the past I got away with one single bank charger with multiple batteries by just moving the hot lead around every week or so but that was just for maintenance charging.
Old 11-18-2016, 06:38 AM
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You have the right idea. 3 bank charger. The real issue is the size of the batteries and the charger output amp. I have a 20 amp charger for an identical system you describe and it works fine. All my batteries are group 31. Higher charge amp will charge the batteries quicker. It depends on how low you take them down. That would most likely apply to the house bank only, as long as the start batteries are properly isolated and are not dragged down with the house loads.



Originally Posted by keithelder View Post
Let's say you have 4 batteries (one for each motor) and two batteries wired together for the house.

Do you A) get a 3 bank battery charger
Or, B) get a 4 bank battery charger

Remember 2 house batteries are tied together. If you charge one, you charge both.

What's the *proper* way to handle this?
Old 11-18-2016, 07:00 AM
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So let's say you have a 30 amp charger with 4 batteries. That means the two house batteries are getting a 10 amp charge. Which equates to about 5amps per battery. Could take a LONG time for them to charge.

If I put a 40amp 4 bank charger. Each battery will get 10 AMP. Even though the house batteries are connected they still get 10 amps each.

Not sure why I wouldn't go with a 4 bank 40amp charger.

I just wanted to make sure my logic and thought process is correct.
Old 11-18-2016, 07:12 AM
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My boat came with four battery banks and a three bank charger from the manufacturer. Only two banks from the charger are used, however. There is a VSR on each battery bank to charge all the batteries. It seemed weird at first but it works well.
Old 11-18-2016, 07:17 AM
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Originally Posted by keithelder View Post
So let's say you have a 30 amp charger with 4 batteries. That means the two house batteries are getting a 10 amp charge. Which equates to about 5amps per battery. Could take a LONG time for them to charge.

If I put a 40amp 4 bank charger. Each battery will get 10 AMP. Even though the house batteries are connected they still get 10 amps each.

Not sure why I wouldn't go with a 4 bank 40amp charger.

I just wanted to make sure my logic and thought process is correct.
Depends on the charger. Some of the newer ones are smart chargers and can distribute the amps as needed per bank. That's the reason I went with the one bank per battery. Some of them need more and some less. Let the charger do the work and just plug it in.
Old 11-18-2016, 08:57 AM
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Originally Posted by edyer View Post
Depends on the charger. Some of the newer ones are smart chargers and can distribute the amps as needed per bank. That's the reason I went with the one bank per battery. Some of them need more and some less. Let the charger do the work and just plug it in.
With that arrangment pay attention to the fuse size on each bank charging lead. I could see a pair of depleted in-parallel batteries drawing more current than what the bank is fused for.
Old 11-18-2016, 09:03 AM
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Originally Posted by Auburn1 View Post
With that arrangment pay attention to the fuse size on each bank charging lead. I could see a pair of depleted in-parallel batteries drawing more current than what the bank is fused for.
That's interesting. I wonder if they can exceed their max rated per bank rate?
Old 11-18-2016, 09:20 AM
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With today's electronic smart chargers, you want one charger bank for each battery. One bank will charge multiple batteries, but it's not optimal.

My boat has three batteries: one starting battery and two tied together for the house bank. My ProMariner ProTournament 3 bank charger can send full amperage (30A) to any one of the 3 batteries.
Old 11-18-2016, 09:32 AM
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Keith, the two house batt's tied together make a single "bank".

So, you need a 3 bank charger.

This is what is typically recommended by the charger manufacturer's.

Nice meeting you btw.
Old 11-18-2016, 09:37 AM
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Originally Posted by keithelder View Post
So let's say you have a 30 amp charger with 4 batteries. That means the two house batteries are getting a 10 amp charge. Which equates to about 5amps per battery. Could take a LONG time for them to charge.

If I put a 40amp 4 bank charger. Each battery will get 10 AMP. Even though the house batteries are connected they still get 10 amps each.

Not sure why I wouldn't go with a 4 bank 40amp charger.

I just wanted to make sure my logic and thought process is correct.
This is incorrect for most of the new chargers - they distribute charge based on demand.

A 30 amp charger can send all 30 amps to any bank. Your cranking batteries won't take much usually and the majority of the amps will be sent to the house bank.

Old 11-18-2016, 09:51 AM
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Originally Posted by rbhankins001 View Post
This is incorrect for most of the new chargers - they distribute charge based on demand.

A 30 amp charger can send all 30 amps to any bank. Your cranking batteries won't take much usually and the majority of the amps will be sent to the house bank.

Aha! I didn't know they would split where they sent output. You da man! Great meeting you and your bride as well.
Old 11-18-2016, 11:16 AM
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Originally Posted by rbhankins001 View Post
This is incorrect for most of the new chargers - they distribute charge based on demand.

A 30 amp charger can send all 30 amps to any bank. Your cranking batteries won't take much usually and the majority of the amps will be sent to the house bank.



I guess that's because the cranking batts are charged when the engines run. My Yamahas have a 2nd set of charging leads that keep my house batt charged too so usually I don't have a large disparity in battery voltage after a trip. I have a 30A Guest, not sure if its smart but it knows how to charge 3 batteries.

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