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Battery Bank Question

Old 09-25-2008, 08:02 PM
  #1  
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Default Battery Bank Question

This question fell flat on my other thread....

Can the same 3 house batteries be wired in both a series configuration for 36v trolling motor AND parallel for 12v accessories?

Thanks guys....

sorry for the double post!
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Old 09-26-2008, 06:51 AM
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Default Re: Battery Bank Question

The answer is no, but you shouldn't need to do that anyway. Wire them in series for the trolling motor, then just connect to ONE of those for your 12V needs. It doesn't actually matter which one you connect to, but to keep it simple and avoid the possibility of accidentally feeding 24V or 36V to your 12V electronics, connect your 12V positive feed to the battery whose ground goes to common ground and not a battery whose ground goes to the next battery. Sorry I can't find a good diagram for this. Hopefully someone will chime in with one.

Now all you need is a 36V charger. Here's some:

http://www.batterystuff.com/battery-...6-volt/marine/

You can also use the Yandina TrollBridge:

http://www.yandina.com/acrobats/Trollbridge36.pdf

Ken
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Old 09-26-2008, 06:57 AM
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Default Re: Battery Bank Question

With three batteries in series, the chain is as strong as the weakest link. If you want to share one of those batteries with a load other than the trolling motor it is dangerous to use any battery other than the the grounded one as some equipment will be 12 or 24 volts higher than other grounds. This can cause fuses to blow or for things like transducers it can cause catastrophic electrolysis problems.
Since batteries have to be matched for series use, if you use one battery unequally you are making a weak link in the series chain. When that battery is discharged, the remaining charge in the other 2 batteries is not only inaccessible but it will rapidly destroy the discharged battery trying to force current through.

So sharing one of the batteries with another load is asking for trouble unless you use a Trollbridge for charging since the Trollbridge puts the batteries in parallel for charging which equalizes the unbalanced charge.

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Old 11-25-2008, 03:28 PM
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Default Re: Battery Bank Question

yandina - 9/26/2008 9:57 AM With three batteries in series, the chain is as strong as the weakest link. If you want to share one of those batteries with a load other than the trolling motor it is dangerous to use any battery other than the the grounded one as some equipment will be 12 or 24 volts higher than other grounds. This can cause fuses to blow or for things like transducers it can cause catastrophic electrolysis problems. Since batteries have to be matched for series use, if you use one battery unequally you are making a weak link in the series chain. When that battery is discharged, the remaining charge in the other 2 batteries is not only inaccessible but it will rapidly destroy the discharged battery trying to force current through. So sharing one of the batteries with another load is asking for trouble unless you use a Trollbridge for charging since the Trollbridge puts the batteries in parallel for charging which equalizes the unbalanced charge.
yandina (an amateur tech working out of his garage) unjustly blasting BOE (a long time supporter of THT) is an absoluteCROCK!!!

http://www.thehulltruth.com/forums/thread-view.asp?tid=223800&start=1

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Old 11-26-2008, 11:36 PM
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Default Re: Battery Bank Question

personally my response is no I don't think you would ever be happy with it. However kenworth trucks used to use both 24 v and 12 v off the same battery bank all charged off the same 12 v alternator back in the 70's and early 80's. So the series parallel switch could be made to do it even so it would be a comprise at best. If I remember correctly while the switch was engaged the load was unequal with all the 12 v charging and circuits running off one side of the bank and the 24 v circuits off both sides so it was only used for short term loads such as starting and running aux equipment. If you want short term use of the 36 v then yes it is possible but would ruin batteries fast for long term use like a trolling motor.
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