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Old 05-21-2017, 01:26 PM   #1
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What is the logic using 6v batteries in series

Why is 6v batteries in series to make 12v so common? Why wouldn't one just get a 12v to start with, half the space... what am I missing?
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Old 05-21-2017, 01:44 PM   #2
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Why is 6v batteries in series to make 12v so common? Why wouldn't one just get a 12v to start with, half the space... what am I missing?

Golf cart batteries are one of the best deep cycle alternatives available. They are designed for incredibly demanding use. A golf course will charge the batteries up overnight, then they get run during the day until almost dead, then get recharged again. These batteries are designed to take that abuse. They are also relatively plentiful and inexpensive. So they often are the best value per Ah compared to other types of batteries. There is no advantage to 6v, it is just that these batteries are only available in 6v.
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Old 05-21-2017, 01:48 PM   #3
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Would you say that they are as robust as 2V batteries, which are generally rated to 80% depletion?
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Old 05-21-2017, 01:54 PM   #4
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Also to get the equivalent ampacity in 12V, the battery would weight 120+ lbs rather than 60+ lbs for 6V. Moving the 6V batteries around is not so challenging as moving 4D or 8D equivalents.
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Old 05-21-2017, 01:55 PM   #5
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2v will require a bunch of jumper cables or links. Lots of connections.
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Old 05-21-2017, 03:29 PM   #6
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Also to get the equivalent ampacity in 12V, the battery would weight 120+ lbs rather than 60+ lbs for 6V. Moving the 6V batteries around is not so challenging as moving 4D or 8D equivalents.

Bingo!! Winner, winner, chicken dinner! Why lift 120lbs when you can split it in half.........
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Old 05-21-2017, 03:31 PM   #7
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One difference between 6 volt and 12 volt banks arises when you build large capacity (measured in Amp-Hours) banks. Lets take a hypothetical bank using 4 - 6 volt GC batts (6V bank for short) and another using 4 - 12 volt batteries (12V bank) of similar physical size. The 6V bank will have 2 batteries in series to make 12 volts and then a second set of 2 in parallel to the first. There is only 2 current flow paths through the entire bank. The 12V bank will be 4 - 12 volt batteries all parallel to each other. There will be 4 current paths through the bank. All is well and good when the banks are new. As the batteries age and the internal resistance increases, the current though the bank will seek the path of least resistance. This leads to unequal current flows though the 12V bank. Some of the 12 volt batteries will be chronically under charged, some over charged, leading to an overall shorter bank lifetime.
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Old 05-21-2017, 05:04 PM   #8
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6 golf cart batteries will fit in the same space as 2 8D's. The two 8D's will have a total amp hour capacity of about 440 amps. The six golf cart batteries will have a total amp hour capacity of about 630 amps. About 50% more capacity in the same space and, as already stated, easier to handle.
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Old 05-21-2017, 05:11 PM   #9
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Two other big factors are their robust build and deep cycling ability...at least in the lead acid family.
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Old 05-21-2017, 05:29 PM   #10
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Wonderful true deep cycling 12V units do exist, but only from a handful of mfg, never in mass retail channels.

99.9% of the 12V labeled "marine deep cycle" used on most (ly smaller but also even large yachts with ignorant owners) are IMO fraudulently labeled, poor choice for deep cycle use.

​To save money up front, the best value by far is Duracell (actually Deka/East Penn) GC-2 from BatteriesPlus or Sam's Club deep cycle golf cart batteries, 2x6V.

If you KNOW your infrastructure and usage patterns will allow these to last 5-7 years, only THEN is it worth spending a lot more per AH for higher quality to get 12-14 years at a time.
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Old 05-21-2017, 06:08 PM   #11
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2v will require a bunch of jumper cables or links. Lots of connections.
Isn't a 12 volt battery just six 2 volt cells rigged in series inside the case?
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Old 05-21-2017, 06:12 PM   #12
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Isn't a 12 volt battery just six 2 volt cells rigged in series inside the case?


Yes, but you don't have to buy and install the cables and maintain the connections.
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Old 05-21-2017, 07:03 PM   #13
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Yes, but you don't have to buy and install the cables and maintain the connections.
You would and that's why I wouldn't use 2v batteries and reinvent the wheel. GC yes, because of the weight.
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Old 05-21-2017, 08:21 PM   #14
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Now, when ya wanna get serious.... just 2 off these 6 volt batteries will do the job.
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Old 05-21-2017, 10:05 PM   #15
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What kind of batteries of batteries are those? ^
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Old 05-21-2017, 11:01 PM   #16
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I just replaced my house batteries. I use 6V GC batteries because of the weight. It took me 3 hours of backbreaking work to get the 4 6V batteries out and another 2.5 hours to get the new ones in. If they were 8D's it would have been impossible for me to get them in or out.
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Old 05-22-2017, 01:41 AM   #17
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What kind of batteries of batteries are those? ^
They are Rolls, made in Canada. They are heavy, but rated at 820 amps each.
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Old 05-22-2017, 05:45 AM   #18
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"Would you say that they are as robust as 2V batteries, which are generally rated to 80% depletion?"

All WLA batts come with a chart.

Deplete then to 50% and you can do it a certain number of times, go all the way to 80% down and you get to do it many times less.

6V are preferred over 12V as the internal spacing allows for more lead , and fewer spacers.

Its the lead that does the work, not the plastic.

With half the number of fill caps 6V watering is faster.

Also the 6V golf carts are made in higher numbers , so are cheaper,per amp hour.
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Old 05-22-2017, 08:22 AM   #19
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6V are preferred over 12V as the internal spacing allows for more lead, and fewer spacers.
The top vendors have excellent 12V batteries that last as long as the lower-voltage equivalents. It's not an inherent difference.

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Also the 6V golf carts are made in higher numbers, so are cheaper, per amp hour.
In a mass retail context, they are all that's available in true deep cycling, and yes those Sam's Clubs are lowest up front investment.

But once you're buying from the top-shelf vendors, not true at all.

Decisions once you're in that segment are based on design factors like serial/parallel layout, longevity and size/weights, not so much price.
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Old 05-22-2017, 08:27 AM   #20
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Yep...until the top of the line batteries have an issue and you have to replace them, even one much earlier than the normal cycle.


Especially purists who say replace the bank at once.


That is a good argument for individual cells....if you can afford the whole deal up front and down the road.


Many people don't keep their boats for the real payback period...so running the numbers is kinda theoretical anyway.


The average boat here can carry enough inexpensive golf cart batteries to survive just fine. At some point, solar and wind is cheaper than more batteries.
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