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Old 12-08-2015, 17:46   #1
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Pros & Cons of 12 volt vs 6 volt batteries

Hi Folks! Looks like we'll be needing to replace the house battery bank in our Triangle 32 before next season, so I've been asking questions. One of the "experts" I've consulted - with a lot of experience with house off-grid solar PV systems - stated that a pair of 6 volt batteries, wired in series, will charge more evenly and therefore have a longer lifespan than (as I'd planned) a pair of 12 volt batteries (group 27) wired in parallel. He could give me no technical description of why this would be so, but stated that two 12 volt batteries (hooked together) in a 12 volt system don't charge evenly, while two 6-volts wired together look like one battery and stay more evenly charged.

So, I'm dubious, but would love input from anyone with ADVANCED knowledge of battery systems. Please, if you don't know more than me, sit this one out. My internet time here on the boat is very limited. Thanks all!
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Old 13-08-2015, 10:19   #2
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Re: Pros & Cons of 12 volt vs 6 volt batteries

I am a fan of 6v batteries but only because they are easier to handle when putting them in and taking them out. It costs extra time and money to install them vs. 12v though as you need the extra cables and terminals to pair them to make 12v and you have to have at least one extra block in between them. I do not know of any other advantages regarding longevity or electrical performance. If just one goes bad you could replace it cheaper than a bigger 12v battery but it is preferable to swap out a set of batteries rather than just one if the batteries have been used very much. I think your advisers need to rethink their advice. When I replace my 8D batteries I am definitely going to 6v but that is because they are easier to handle and locate.
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Old 13-08-2015, 10:56   #3
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Re: Pros & Cons of 12 volt vs 6 volt batteries

Batteries in parallel do not behave as well as those in series. Mostly due to charging issues. Search the solar power users for some good detailed info as to why.
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Old 13-08-2015, 11:32   #4
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Re: Pros & Cons of 12 volt vs 6 volt batteries

6v golf cart batteries generally have much thicker plates than their 12v "deep cycle" counterparts. i.e. the 6v battery is truly a deep cycle battery where most of the 12v batteries are dual-purpose.

They're also relatively cheap. They're also much easier to handle than 4d or 8d batteries. Bang-for-buck, for a SLA, I'd _always_ go for 6v batteries.

Search this forum, any RV forum, you'll find plenty of responses on this specific question.
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Old 13-08-2015, 11:45   #5
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Re: Pros & Cons of 12 volt vs 6 volt batteries

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6v golf cart batteries generally have much thicker plates than their 12v "deep cycle" counterparts. i.e. the 6v battery is truly a deep cycle battery where most of the 12v batteries are dual-purpose.

They're also relatively cheap. They're also much easier to handle than 4d or 8d batteries. Bang-for-buck, for a SLA, I'd _always_ go for 6v batteries.

Search this forum, any RV forum, you'll find plenty of responses on this specific question.
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Old 13-08-2015, 12:11   #6
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Re: Pros & Cons of 12 volt vs 6 volt batteries

They may exist but I am not aware of any true deep cycle, group 27 batteries. I see batteries labeled "marine deep cycle" but they are not the real deal. Most bang for the buck, genuine deep cycle, heavy duty will be a 6V golf cart, GC2 series like the Trojan T102 or similar.

As far as charging difference with your small bank of two 12V in parallel vs two 6V in series I doubt you could see or measure any difference in how they charge or in a shorter life span due to that. Buying a real deep cycle will have a much greater impact.

NOTE: That does assume the proper cables connecting the batteries, clean, tight connections, etc. Small wires, poor connections or anything else that can cause a voltage drop between batteries in a parallel pair could make a difference.
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Old 13-08-2015, 13:17   #7
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Re: Pros & Cons of 12 volt vs 6 volt batteries

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Originally Posted by jeepbluetj View Post
6v golf cart batteries generally have much thicker plates than their 12v "deep cycle" counterparts. i.e. the 6v battery is truly a deep cycle battery where most of the 12v batteries are dual-purpose.

They're also relatively cheap. They're also much easier to handle than 4d or 8d batteries. Bang-for-buck, for a SLA, I'd _always_ go for 6v batteries.

Search this forum, any RV forum, you'll find plenty of responses on this specific question.

This is the best answer, there are just simply no "real" 12V deep cycle batteries, it's not charge behavior, but having more, lighter and cheaper batteries as opposed to fewer, heavier, more expensive ones just doesn't make sense either.
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Old 13-08-2015, 13:21   #8
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Re: Pros & Cons of 12 volt vs 6 volt batteries

https://youtu.be/k5nM5jlPZjI

At 10:46
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Old 13-08-2015, 13:31   #9
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Re: Pros & Cons of 12 volt vs 6 volt batteries

As someone that has used both 12V and 6V house banks, 6V is FAR superior from a depth of charge and lifetime # of charges. Of course having the wiring installed correctly, so each battery is balanced with the load helps lots too.

Then there is orentation of the batteries which I learned from Mainesails website. You ideally want the long axis of the batteries sitting in the port /starboard direction. Due to heeling of the boat uncovering the plates when sailing briskly. Placing the batteries with the long access across the boat, reduces that issue.
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Old 13-08-2015, 13:35   #10
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Re: Pros & Cons of 12 volt vs 6 volt batteries

Quote:
Originally Posted by jeepbluetj View Post
6v golf cart batteries generally have much thicker plates than their 12v "deep cycle" counterparts. i.e. the 6v battery is truly a deep cycle battery where most of the 12v batteries are dual-purpose.

They're also relatively cheap. They're also much easier to handle than 4d or 8d batteries. Bang-for-buck, for a SLA, I'd _always_ go for 6v batteries.

Search this forum, any RV forum, you'll find plenty of responses on this specific question.
That's it in a nutshell. The market for deep cycle golf cart batteries is huge compared to the market of batteries to cheap tight wad boater
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Old 13-08-2015, 14:13   #11
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Re: Pros & Cons of 12 volt vs 6 volt batteries

Hmmm,

My house bank is two 4D AGM batteries. Replacing them by myself was not one of my better decisions, I have the crushed disk to prove THAT. In fact my back is still aching after 7 yrs.

My last boat had 6v golf cart batteries. How do my 4D's fare in this thread. Keep in mind I have limited access for maintaining wet cells.

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Old 13-08-2015, 14:28   #12
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Re: Pros & Cons of 12 volt vs 6 volt batteries

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Keep in mind I have limited access for maintaining wet cells.
I consider this a separate item you have to consider if the there is a physical practical reason to not have wet cells. OTOH I checked my wet cells for the first time in 3 months last week and they didn't need any water in one bank so I didn't even check the other bank.
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Old 13-08-2015, 17:29   #13
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Re: Pros & Cons of 12 volt vs 6 volt batteries

Without regards as to which battery type or voltage is "better", the general rule is that overall reliablity goes down as you add more parts to the system. Thus 4 6-volt GC batteries (with 12 separate cells) will be twice as reliable as 4 Group 31 12-volt batteries (with 24 cells) while having about the same overall AH capacity.


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Old 14-08-2015, 01:30   #14
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Re: Pros & Cons of 12 volt vs 6 volt batteries

US Battery says that the cycle life of their 12 volt FLA batteries is as good as their 6 volt GC's. So why are GC's any better?
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Old 14-08-2015, 02:29   #15
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Re: Pros & Cons of 12 volt vs 6 volt batteries

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Originally Posted by cabo_sailor View Post
Hmmm,



My last boat had 6v golf cart batteries. How do my 4D's fare in this thread. Keep in mind I have limited access for maintaining wet cells.

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they make agm golf carts
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