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post #1 of 12 Old 03-11-2012 Thread Starter
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Replacing 12 volt batteries with 6 volt

I am replacing 3 batteries that are configured as 2 for the house bank and 1 for starting with 2, 6 volt Trojan batteries. When I bought the boat, I updated the battery switch to a Blue Seas Switch that controls the rate of charging and prevents overcharging from solar and trickle chargers. for the house bank and starting battery and gives the option of choosing 1 or 2 or combining them.
My question is: If 6 volt batteries are connected in series to provide the necessary 12v, then it seems I will no longer have a dedicated starting battery.
Is this correct?

Thanks for your help.

Larry
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post #2 of 12 Old 03-11-2012
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Re: Replacing 12 volt batteries with 6 volt

Yes, the new set up you describe would seem to eliminate your starting battery.
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post #3 of 12 Old 03-11-2012
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Re: Replacing 12 volt batteries with 6 volt

Not necessarily.
"I am replacing 3 batteries that are configured as 2 for the house bank and 1 for starting with 2, 6 volt Trojan batteries"
Your two new 6V batteries can be combines into one 12v battery, or battery bank, whichever term you prefer. That one new battery can be used to replace your previous house battery bank (of 2 twelve-volt batteries) and you can always leave one of the three old batteries as a dedicated starting battery, if any of them has any life left in it.
Or, you can simply use the two new batteries as your only "battery bank" and wire it up to position 1 or 2, leaving the other one unused, on your battery switch. If you're going to do that, I'd suggest replacing the switch with a simple "On/Off" type, which eliminates any possible confusion or damage from someone selecting the wrong position (i.e. "2" if there's nothing connected to it) on the existing battery switch.
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post #4 of 12 Old 03-11-2012
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Re: Replacing 12 volt batteries with 6 volt

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Originally Posted by justonemoreproject View Post
When I bought the boat, I updated the battery switch to a Blue Seas Switch that controls the rate of charging and prevents overcharging from solar and trickle chargers. for the house bank and starting battery and gives the option of choosing 1 or 2 or combining them.

Thanks for your help.

Larry
The only Blue Seas item that comes close to what you describe is their Dual Circuit Plus switch which when combined with an ACR is packaged as an Add a Battery.

It combines the batteries in parallel when a charge source is present just the same way as if they are wired together and separates them when the voltage drops below 12.35 for 10 seconds or 12.75 for 30 seconds. It does not control charging in any other way.

6 volt golf cart batteries are certainly the best value and you will have a house bank of between 225 and 240 AH depending on brand.

As posted if one of the 3 batteries toy currently have is in good condition you can keep it as a dedicated start battery.

Brian
Living aboard in Victoria Harbour
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Re: Replacing 12 volt batteries with 6 volt

Thanks for the great info. I like the idea of having just 2 batteries on starboard to correct the boats trim. (she lists a little to port). Also, shedding 65 pounds would be an advantage as well, but I like the idea of having a starting battery that is shielded from running all the way down. Space is limited for a battery that is taller then a Group 27 without some modifications. I think I heard somewhere that storing batteries in the engine compartment is a bad idea. Is that correct?
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Re: Replacing 12 volt batteries with 6 volt

Engine compartments are hot and full of vibration, all bad for batteries. OTOH that usually means shorter battery cables. But getting your batteries out of the heat and vibration would be a good thing.

A Group27 or even a G24 battery might be good enough as a starting battery. Cheap enough to just buy one and replace it more frequently. Apparently WalMart sells their SLI batteries with a 3-year free replacement warranty. An unscrupulous fellow might just buy one of those and after 30 months, toast it for a new one.
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post #7 of 12 Old 03-15-2012 Thread Starter
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Re: Replacing 12 volt batteries with 6 volt

OK. I got 2 6v batteries. I saw some diagrams that showed 4 batteries connected both in parallel and series. Can I do that with just 2 6v and is it a good idea? Also, one of the 12v i have might still be a little tired but still working. Can I use that as a starting battery even though its worn? By the way, my switch is Blue Seas Dual Circuit Plus that is connected to a Blue Seas Battery LInk ACR. I can set it charge to any rate I want to. I guess that I should change it to a different voltage for the Trojans!
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Re: Replacing 12 volt batteries with 6 volt

"OK. I got 2 6v batteries. I saw some diagrams that showed 4 batteries ...Can I do that with just 2 6v and is it a good idea?"

You really want to get and read "The 12 volt doctor" or "the 12 volt bible" or a similar good book on boat electrics before you fry something.

It was set up for FOUR now you have TWO pretty obviously, no, you cannot set up 2 the way 4 were set. The only thing you can do with two 6v batteries is set tme up in series to make one 12v battery bank.

"I can set it charge to any rate I want to. I guess that I should change it to a different voltage for the Trojans! "
Rate is AAMPERAGE and has got nothing to do with VOLTAGE. Again, buy and read nice little book to avoid major problems. You will leave the charger set for 12v wet acid batteries, and set the rate to match the capacity of your battery bank. Which will be clear after reading the little book.

Your tied 12v battery probably will be good enough to keep as a starting battery. You may find that after equalizing it, and possibly topping up electrolyte, it is good enough for a starting battery. If not, go to Walmart, buy a properly sized starting battery and enjoy a 3-year replacement warranty and a good price.
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Re: Replacing 12 volt batteries with 6 volt

Thanks for your help. My old batteries were connected in parallel. My question is, can 2 batteries be connected in series and parallel at the same time and is that a good idea.
Also, i have a new trickle charger that charges at 1.5 amps and will turn off when the batteries are fully charged.
As for books, I am getting the Sailboat Electronics Simplified book.

Thanks again for all your great hel!

Larry
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Re: Replacing 12 volt batteries with 6 volt

"can 2 batteries be connected in series and parallel at the same time and is that a good idea."
No, that would be called a mess or a short circuit and start a fire or battery explosion. You can connect two batteries in series OR in parallel but not both at the same time.
One way doubles (combines both) the output voltage, the other doubles (combines both) the output amperage.

Be careful with the batteries, Larry. Most folks don't realize the a single 12-volt car battery can put out over 3000 amps into a short circuit, and if your wedding ring is part of that short, it will amputate your finger. A significant number of folks are blinded in the US every year when they literally blow up their car batteries while trying to jump start cars, too.

A 1/5A charger will eventually charge them, and is a good way to keep them in shape whilenot in use, but once you read the book I suspect you'll want something better.
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