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Old 11-02-2018, 07:26   #1
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Batteries Groups

Hello.

I purchased a sailboat with 5 house batteries and 1 start battery. The battery banks are separated with a switch.
Right now the house bank is 2 X 27 group lead acid, 1 x 24 group lead acid and 2 x 6 volt lead acid (golf cart).
My question is I would like to replace all the house batteries before I leave for a long trip. Should I go with all group 24 (5) batteries or 3 group 24 and 2 group 27?
I don't have room for more then 2 group 27 batteries. Is there any problems when you mix group 24 and group 27 in the same bank?
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Old 11-02-2018, 09:01   #2
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Re: Batteries Groups

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Hello.
I don't have room for more then 2 group 27 batteries. Is there any problems when you mix group 24 and group 27 in the same bank?
It is not a significant problem if all the batteries are purchased and installed together. You might lose 3-5% lifespan as the different sized batteries will not charge/discharge equally causing an efficiency problem over time.

You could isolate the different batteries into two separate banks by adding another battery switch.
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Old 11-02-2018, 09:52   #3
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Re: Batteries Groups

If the new batteries are for house loads do not get group 27, group 24, etc. You really want a true deep cycle battery for house loads and those are at the most optimistic what might be a heavy duty or dual use battery but definitely NOT deep discharge.

By far the better choice of the options you have is to use 6V golf cart batteries, size GC2. They are usually the cheapest (at least in the US) and are true deep cycle batteries.
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Old 11-02-2018, 11:18   #4
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Re: Batteries Groups

I use 6v golf cart batteries on my sailboat and my travel trailer. For most applications, they can't be beat. Highly recommend you do some internet searching and study on golf cart batteries and their advantages. Try marinehowto.com for some of the best info.

A bank of four 6v for your house, and a 12v starter battery would probably make a lot of sense. Of course, never run the switch on "both".

A good compromise golf cart battery is the Duracell (made by East Penn) which is sold by Sam's Club.
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Old 11-02-2018, 13:03   #5
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Re: Batteries Groups

don't mix batteries. try to fit all golf carts. can you fit 4 of those?

24 and 27 are not good deep cycle batteries.
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Old 11-02-2018, 19:15   #6
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Re: Batteries Groups

All the same size and model, ideally same mfg date, as recent as possible.

There are some - very few and expensive - automotive sized true deep cycle.

GCs are best value, stick to flooded.

​The best battery value by far is Duracell (actually Deka/East Penn) FLA deep cycle golf cart batteries, 2x6V, around $200 per 200+AH pair from BatteriesPlus or Sam's Club.

If Trojan T-105s are within a 20% premium, maybe worth it, RE variant a big step up but pricey.

Crown and US Battery are great, Rolls Surette the best.
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Old 12-02-2018, 05:18   #7
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Re: Batteries Groups

Quote:
Originally Posted by Atango View Post
I purchased a sailboat with 5 house batteries and 1 start battery. The battery banks are separated with a switch.
Right now the house bank is 2 X 27 group lead acid, 1 x 24 group lead acid and 2 x 6 volt lead acid (golf cart).
My question is I would like to replace all the house batteries before I leave for a long trip. Should I go with all group 24 (5) batteries or 3 group 24 and 2 group 27?
I don't have room for more then 2 group 27 batteries. Is there any problems when you mix group 24 and group 27 in the same bank?

Interesting mish-mash; wonder how that came about. General rule of thumb is all the same size (BCI Group), chemistry (e.g., lead-acid), type (i.e., don't mix FLA, AGM or Gel in a single bank), and age.

Your mish-mash suggests you may have room for four or even six 6V deep cycle batteries, and that'd be my first choice, were it me.

If they're easy to service, you don't mind doing it, and you don't have off-gassing issues, decent flooded lead-acid (e.g., Trojan T105s or others) would be OK. If they're not easy to service, or if you're disinclined to do your part... or if you have worries about off-gassing, then AGMs can be a good choice... at greater expense.

-Chris
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Old 12-02-2018, 05:22   #8
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Re: Batteries Groups

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don't mix batteries. try to fit all golf carts. can you fit 4 of those?

24 and 27 are not good deep cycle batteries.
Thanks
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Old 12-02-2018, 05:23   #9
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Re: Batteries Groups

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Originally Posted by john61ct View Post
All the same size and model, ideally same mfg date, as recent as possible.

There are some - very few and expensive - automotive sized true deep cycle.

GCs are best value, stick to flooded.

​The best battery value by far is Duracell (actually Deka/East Penn) FLA deep cycle golf cart batteries, 2x6V, around $200 per 200+AH pair from BatteriesPlus or Sam's Club.

If Trojan T-105s are within a 20% premium, maybe worth it, RE variant a big step up but pricey.

Crown and US Battery are great, Rolls Surette the best.
Thanks for the information
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Old 12-02-2018, 06:43   #10
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Re: Batteries Groups

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If they're easy to service, you don't mind doing it, and you don't have off-gassing issues, decent flooded lead-acid (e.g., Trojan T105s or others) would be OK. If they're not easy to service, or if you're disinclined to do your part... or if you have worries about off-gassing, then AGMs can be a good choice... at greater expense.

-Chris
Just bear in mind that AGMs don't require watering so less maintenance there but are a little pickier about charging so there is a trade off.
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Old 12-02-2018, 10:02   #11
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Re: Batteries Groups

And more expensive, and don't last as long.
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Old 12-02-2018, 10:53   #12
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Re: Batteries Groups

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And more expensive, and don't last as long.

Yes, more expensive. I dunno that the "don't last as long" is gospel.

Our 12Vs faired well, almost 12 seasons. I more recently replaced that bank with Lifeline GC2s, of course hoping for equal lifetime... Too early to tell, though.

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Old 12-02-2018, 11:13   #13
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Re: Batteries Groups

The standard replacement time is 80% residual capacity.

Most people go way past that, after 70-75% much higher risk of unexpected failure.

Lifeline are a top-notch AGM maker, but even eight years would be optimistic for liveaboard use, require a meticulous coddling regime, average DoD much lower than the usual 50%

Obviously just using until the bank fails will get you more years.

So many variables, but all things being equal FLA do last longer, and withstand occasional abuse much more robustly.
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Old 13-02-2018, 04:54   #14
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Re: Batteries Groups

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The standard replacement time is 80% residual capacity.

Most people go way past that, after 70-75% much higher risk of unexpected failure.

Lifeline are a top-notch AGM maker, but even eight years would be optimistic for liveaboard use, require a meticulous coddling regime, average DoD much lower than the usual 50%

Obviously just using until the bank fails will get you more years.

So many variables, but all things being equal FLA do last longer, and withstand occasional abuse much more robustly.


We're not liveaboards (usually), it's easy to treat our batteries right, and the primary reason we've chosen AGMs is about access difficulty...

But I don't think I've ever seen any stats that suggest AGMs don't last as long as FLAs... under identical circumstances. Hard to find those "identical circumstances."

I expect our Lifelines probably won't last as long as our previous Odysseys, but more because we've also added an inverter on that bank... which in turns means some additional loading (from time to time) that would previously have been serviced by the genset. Nothing too serious, just morning coffee and maybe afternoon popcorn or happy hour hors d'ouevres... or maybe TV while underway... but still, no longer "identical circumstances."

-Chris
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Old 13-02-2018, 06:09   #15
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Re: Batteries Groups

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We're not liveaboards (usually), it's easy to treat our batteries right, and the primary reason we've chosen AGMs is about access difficulty...

But I don't think I've ever seen any stats that suggest AGMs don't last as long as FLAs... under identical circumstances. Hard to find those "identical circumstances."

I expect our Lifelines probably won't last as long as our previous Odysseys, but more because we've also added an inverter on that bank... which in turns means some additional loading (from time to time) that would previously have been serviced by the genset. Nothing too serious, just morning coffee and maybe afternoon popcorn or happy hour hors d'ouevres... or maybe TV while underway... but still, no longer "identical circumstances."

-Chris
Have not personally read any long term tests on AGM vs FLA batteries but numerous reports from users seem to indicate no problem with long life IF the AGMs are properly maintained. Since I occasionally abuse my batteries and have very easy access I'll stick with FLAs.
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