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Old 24-10-2018, 12:23   #1
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Mixing 6V and 12V batteries

Hi. I need to replace the battery for the thruster. Could I use 2x 6V batteries for this when all the other batteries (starter and house) are all 12V (wet cell) and all are connected to the battery charger? I apologise if this is a neophyte's question. Also, it is inevitable that the battery manufacturer will be different as the others came with the boat.
Thanks
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Old 24-10-2018, 13:31   #2
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Re: Mixing 6V and 12V batteries

Yes.

As long as it is a separate bank, only connected to others when charging is active, NP at all.

The charge voltage the mfg specs should match what they get for longevity.
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Old 24-10-2018, 13:45   #3
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Re: Mixing 6V and 12V batteries

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Originally Posted by john61ct View Post
Yes.

As long as it is a separate bank, only connected to others when charging is active, NP at all.

The charge voltage the mfg specs should match what they get for longevity.
Yes, what he said, but to clarify one point. You did say wet cell but to be perfectly clear all same battery type IE all FLA or all gel or all AGM, etc.
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Old 24-10-2018, 15:30   #4
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Re: Mixing 6V and 12V batteries

Many thanks for the replies
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Old 24-10-2018, 18:16   #5
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Re: Mixing 6V and 12V batteries

Yes GEL is different, but AGM and FLA can usually find a common setpoint.

Or if not, optimize for big expensive House bank, let the smaller / cheaper bank suffer a little, NBD.
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Old 25-10-2018, 04:33   #6
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Re: Mixing 6V and 12V batteries

Re "GEL is different, but AGM and FLA can usually find a common setpoint".
Thanks for this. It's the first time I noticed someone suggesting that AGM and flooded can be mixed. A marine electrician had previously included AGMs for a specific application where space was very limited.
S
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Old 25-10-2018, 05:36   #7
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Re: Mixing 6V and 12V batteries

Just look at the batt mfg published specs.

I do say this assuming you are calibrating charge source(s) to ensure precise compliance with them.

If they are not custom adjustable, you will have less flexibility.

If the big expensive House bank is AGM, certainly do not overcharge them just because the cheap FLA Starter batt can take it.

Common sense.
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Old 25-10-2018, 06:15   #8
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Re: Mixing 6V and 12V batteries

Quote:
Originally Posted by Srah 1953 View Post
Re "GEL is different, but AGM and FLA can usually find a common setpoint".
Thanks for this. It's the first time I noticed someone suggesting that AGM and flooded can be mixed. A marine electrician had previously included AGMs for a specific application where space was very limited.
S

Your best bet for bowthruster batteries are dry spiral cranking batteries. You do not want deep cycle batteries for this application. The beauty of these batteries is that they can be charged at a higher rate than regular FLA batteries and most AGM batteries and they can withstand a depleted charge for longer periods much better than most other types, especially traction. They tend to not self discharge as quickly as wet cell or agm's.



They also have the added benefit of not requiring watering and can be mounted in any position. Check out the Optima web site for manufacturers charging instructions and you will see that these batteries are best suited for your application.
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