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Old 19-05-2013, 18:18   #1
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6V bank to replace 12V bank

I am considering replacing my long serving 12V bank (3 house + 1 engine) with 6V batteries. I would appreciate others experience with this change, battery recommendations, things to avoid, best practices, etc.

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Old 19-05-2013, 18:45   #2
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Re: 6V bank to replace 12V bank

if you're talking 'golf cart' batteries, i'd say go ahead and do it. they withstand the constant charging/discharging cycle better than most typical boat batteries, and aren't that expensive. i've been using them for years.

used to have a full bank of trojan t-105's. but when they finally gave out and i went shopping i discovered that they had simply priced themselves out of my range. so i went to sam's and bought their brand at about $80 apiece. after two years, so far so good.
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Old 19-05-2013, 18:45   #3
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Re: 6V bank to replace 12V bank

I'd keep a 12-volt starting battery, using 6-volt golf cart batteries for the house bank only. The Sam's Club golf carts are a great value around here.
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Old 19-05-2013, 18:58   #4
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Re: 6V bank to replace 12V bank

The other advantage is that two 6V batteries are easier to handle than a single 12V battery
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Old 19-05-2013, 19:05   #5
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Re: 6V bank to replace 12V bank

Sam's Club by all means UNLESS you happen to live in Florida...around Ft Lauderdale for instance. There is a seller there discussed last year here in the forums who sold the Trojan 105s for about the same price as Sam's golf cart (Penn) batteries. MaineSail gave thought at that time about sending a truck down there for a load of them

EDIT!!! If you do embark on this project, you should seriously consider BATTERY FUSES!!!
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Old 19-05-2013, 19:49   #6
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Re: 6V bank to replace 12V bank

Quote:
Originally Posted by nigel1 View Post
The other advantage is that two 6V batteries are easier to handle than a single 12V battery
of the same total amperage....
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Old 19-05-2013, 20:40   #7
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Re: 6V bank to replace 12V bank

better to put 2 6 volt in series than 2 12 volt in parallel. Fewer cells to keep watered, and too many strings in parallel is a bad idea.
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Old 20-05-2013, 13:28   #8
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Re: 6V bank to replace 12V bank

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Originally Posted by boat_alexandra View Post
better to put 2 6 volt in series than 2 12 volt in parallel. Fewer cells to keep watered, and too many strings in parallel is a bad idea.
True except for one provision.

It is ESSENTIAL that batteries in series be matched for as many parameters as possible, age, chemistry, capacity, manufacturer etc.

This is AUTOMATIC when you purchase or replace a 12 volt battery.

To achieve this with 6 volt batteries in series, ALWAYS replace both batteries with matched pairs when one of them dies.
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Old 20-05-2013, 13:41   #9
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Re: 6V bank to replace 12V bank

I made this switch over the winter using the Sam's Club golf cart batteries for house and a Gr 27 for start. So far, so good. The switch implies going from four batteries to five (2 pairs of 6v + the start battery). The golf cart batteries have similar footprints to a Gr 27, but they are taller. I didn't have room for the extra battery and needed to reconfigure the boxes to hold the taller profile. It wasn't a problem, but consider where everything will fit.
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Old 20-05-2013, 13:56   #10
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The other advantage is that two 6V batteries are easier to handle than a single 12V battery
Says you. I just went to pull the old T105s that came with my boat only to discover they are in fact T305h's, at a brisk 98 pounds each. Whoever manhandled those beasts into the engine room was a masochist! I just about killed myself and I've only just got the first one out.

And here I was wondering how I was going to get the handle-less GC2s I got at Costco in there... That's now the least of my worries...

JRM

-- oh, and golf cart batteries rock. These that I'm replacing are almost 12 years old, sat unused for six of those, and I still got last season's trips out of them...
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Old 20-05-2013, 14:07   #11
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Re: 6V bank to replace 12V bank

Quote:
Originally Posted by JRM View Post
Says you. I just went to pull the old T105s that came with my boat only to discover they are in fact T305h's, at a brisk 98 pounds each. Whoever manhandled those beasts into the engine room was a masochist! I just about killed myself and I've only just got the first one out.

And here I was wondering how I was going to get the handle-less GC2s I got at Costco in there... That's now the least of my worries...

JRM

-- oh, and golf cart batteries rock. These that I'm replacing are almost 12 years old, sat unused for six of those, and I still got last season's trips out of them...
When I got my EGC-2's, they gave me a strap that latches onto the case. It makes moving the batteries and positioning them in the box a whole lot easier. If your Sam's Club is close by, it might be worth asking if they have the straps in stock.
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Old 20-05-2013, 14:23   #12
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Re: 6V bank to replace 12V bank

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Originally Posted by Andina Marie View Post
True except for one provision.

It is ESSENTIAL that batteries in series be matched for as many parameters as possible, age, chemistry, capacity, manufacturer etc.

This is AUTOMATIC when you purchase or replace a 12 volt battery.

To achieve this with 6 volt batteries in series, ALWAYS replace both batteries with matched pairs when one of them dies.
I wonder! Have you considered the impact of parallel 12s where the internal resistances are different? So now it becomes a trade off between internal battery resistance for parallel banks and a series configuration where the analogy is similar to that of the weakest chain link.
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Old 20-05-2013, 14:28   #13
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Re: 6V bank to replace 12V bank

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Originally Posted by boat_alexandra View Post
better to put 2 6 volt in series than 2 12 volt in parallel. Fewer cells to keep watered, and too many strings in parallel is a bad idea.

I agree but not for the reasons you state. If the batteries are properly charged with a now common 3+ stage charger, the water level may never change. I never check the water levels in our cars and for that matter, the water levels in our boat batteries have stayed put for the last couple of years.
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Old 20-05-2013, 14:50   #14
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Re: 6V bank to replace 12V bank

You will need a whole new set of cables so buying a crimper might be a good idea. The good ones cost around $200+.

This might not be relevant, but check that your battery box is not restricted in height. Golf carts are much higher than 12v.
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Old 20-05-2013, 15:31   #15
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Re: 6V bank to replace 12V bank

Also, terminals layout may differ. If there are buses or thick cables involved, you may have to modify. I guess someone mentioned.

I do not like 6V batteries in 12V systems. Even less in 24V systems. My say is stick to 12V batteries for 12V system, unless the 6V cells are the better option.

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