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Old 10-13-2016, 11:10 AM   #21
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Originally Posted by Pilou View Post
Thanks for clear and precise explanation.
Then if Ah capacity stays the same what is the good of having 6 x 6v batteries wired in series (actually my service battery bank) instead of 3 x 12v batteries wired in parallel?

Most 12V "marine" flooded batteries are simply cheap imposters and not a true deep cycle product. In other words they are deep cycle in name only.

I actually posed the below question to one of the major US battery manufacturers of both marine "deep cycle" and golf, RE and industrial deep cycle batteries:

Question asked by MarineHowTo.com:

"If the GC2, GC-12 or L16's were cycled using the same cycle life testing as the 12V Group 24, 27, 31 etc. what would that outcome, in cycle life, actually look like? Is it fair to suggest a GC2, GC12 or L16 battery has double to triple the lab cycle life, to 50% DOD, than the 12V 24, 27 & 31 "deep cycles" do?"


Senior Battery Engineer - Major US Battery Manufacturer:

"Yes, for packs of equivalent energy content (voltage * capacity) the Golf Car types and L16's are 2-3 times better than the DC automotive sizes (24, 27 and 31)."


A typical GC-2, or golf car battery, is intended and specifically designed for daily deep cycling where as a 12V Group 24, 27, 29, 30, 31 & most 4D and 8D flooded batteries (Rolls & Dyno being the only exception I know of) are really lightly built "dual purpose" automotive grade batteries that don't cycle nearly as well. Trojan puts their 12V "marine" batteries SCS-150 (G-24), SCS-200 (G-27) & SCS-225 (G-31) at just half the cycles of their T-105 or T1275 golf car batteries.

When buying batteries it is not just $$ per Ah it is cost per Ah plus expected cycle life that yields the best value. It's pretty hard to beat a 6V GC-2 battery in an Ah's to $$ to cycles number crunch game.

That said there are also 12V golf car and industrial sweeper scrubber batteries available too such as Trojan's J150, T1275 or J185 and East Penn, US Battery, Crown and others also offer a GC12 (golf car 12V) or J185 type form factor.

Another advantage of using series/parallel, to build capacity, is that you have less batteries wired in parallel which reduces your chances of an internal short leading to thermal run-away.

When you get frantic text messages like this, from your customers, you tend to think about these things more than a DIY..



Below is an example of a bank of 6 Trojan T1275's, 900Ah's of parallel 12V golf car batteries, that had one short internally (they were well beyond their useful life though). This means the owner had the inverter/charger plus 750 Ah's of parallel batteries all trying to charge the one battery that was now a 10V battery. 154F is simply dangerous!!

While these deep cycle golf car batteries lasted an exceptional 6.5 years, on a 24/7/365 world cruising boat, I am not a big fan of this many batteries in parallel for this exact reason. This was not my design, wiring or installation, I inherited it. A series/parallel bank would have reduced the number of paralleled batteries that could thermally run away in the event of a cell shorting.

Sadly the marine charging industry has failed us on safely charging parallel batteries by supplying just one battery temp sensor per charger or charge source. A real joke and a travesty. While some do have the option of two temp sensors this is rare.

House load demands are getting larger and larger yet the marine charging industry has done NOTHING to address the safety issues of paralleled batteries such as temp sensor options for each battery..

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Old 10-13-2016, 11:19 AM   #22
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I'd like to point out we've exceeded the 20 post threshold. These posts have been in series so no anchors have been harmed.
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Old 10-13-2016, 11:43 AM   #23
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Quote:
Originally Posted by CMS View Post


A typical GC-2, or golf car battery, is intended and specifically designed for daily deep cycling where as a 12V Group 24, 27, 29, 30, 31 & most 4D and 8D flooded batteries (Rolls & Dyno being the only exception I know of) are really lightly built "dual purpose" automotive grade batteries that don't cycle nearly as well...

Another advantage of using series/parallel, to build capacity, is that you have less batteries wired in parallel which reduces your chances of an internal short leading to thermal run-away.
CMS

Thanks for a clear an informative post!

Do the above statements hold true for comparable AGM's?

e.g. 2- GC2-AGM's in series a better choice than a 8D-AGM
(from a life standpoint - I realize there is a small difference in AH capacity)
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Old 10-13-2016, 11:47 AM   #24
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Good point about risk of thermal runaway with paralleled batts with one getting a shorted cell. Seen the havoc from that first hand.
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Old 10-13-2016, 11:50 AM   #25
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I'd like to point out we've exceeded the 20 post threshold. These posts have been in series so no anchors have been harmed.
Yes, and the OP's question was answered succinctly and accurate by Ski in the first response. Now the OP is probably confused as hell.

Welcome to internet forums. We can't help ourselves, can we.

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Old 10-13-2016, 12:18 PM   #26
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Great info, CMS! Thanks a million!
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Old 10-13-2016, 12:52 PM   #27
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Originally Posted by denverd0n View Post
Cost and weight. The 6 volt batteries will each weigh much less (not quite half, but close) to what an equivalent 12 volt battery would weigh. Makes them easier to move around. Also, at least here in Florida, because of the huge market for 6 volt golf cart batteries, it is cheaper to get two 6 volt batteries than it is to get one, larger, 12 volt battery.

As to the series/parallel thing. I used to shop at a PAC-n-SAV store. You know, one of those warehouse stores kind of similar to Costco or Sam's Club. So I just remember pac-n-sav: Parallel Adds Current-n-Series Adds Voltage.
Interesting information. Thank you !
Sadly we don't have Costco here in France but I have a Costco card for when I'm in the US.
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Old 10-13-2016, 12:56 PM   #28
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Originally Posted by CMS View Post
Most 12V "marine" flooded batteries are simply cheap imposters and not a true deep cycle product. In other words they are deep cycle in name only.

I actually posed the below question to one of the major US battery manufacturers of both marine "deep cycle" and golf, RE and industrial deep cycle batteries:

Question asked by MarineHowTo.com:

"If the GC2, GC-12 or L16's were cycled using the same cycle life testing as the 12V Group 24, 27, 31 etc. what would that outcome, in cycle life, actually look like? Is it fair to suggest a GC2, GC12 or L16 battery has double to triple the lab cycle life, to 50% DOD, than the 12V 24, 27 & 31 "deep cycles" do?"


Senior Battery Engineer - Major US Battery Manufacturer:

"Yes, for packs of equivalent energy content (voltage * capacity) the Golf Car types and L16's are 2-3 times better than the DC automotive sizes (24, 27 and 31)."


A typical GC-2, or golf car battery, is intended and specifically designed for daily deep cycling where as a 12V Group 24, 27, 29, 30, 31 & most 4D and 8D flooded batteries (Rolls & Dyno being the only exception I know of) are really lightly built "dual purpose" automotive grade batteries that don't cycle nearly as well. Trojan puts their 12V "marine" batteries SCS-150 (G-24), SCS-200 (G-27) & SCS-225 (G-31) at just half the cycles of their T-105 or T1275 golf car batteries.

When buying batteries it is not just $$ per Ah it is cost per Ah plus expected cycle life that yields the best value. It's pretty hard to beat a 6V GC-2 battery in an Ah's to $$ to cycles number crunch game.

That said there are also 12V golf car and industrial sweeper scrubber batteries available too such as Trojan's J150, T1275 or J185 and East Penn, US Battery, Crown and others also offer a GC12 (golf car 12V) or J185 type form factor.

Another advantage of using series/parallel, to build capacity, is that you have less batteries wired in parallel which reduces your chances of an internal short leading to thermal run-away.

When you get frantic text messages like this, from your customers, you tend to think about these things more than a DIY..

Below is an example of a bank of 6 Trojan T1275's, 900Ah's of parallel 12V golf car batteries, that had one short internally (they were well beyond their useful life though). This means the owner had the inverter/charger plus 750 Ah's of parallel batteries all trying to charge the one battery that was now a 10V battery. 154F is simply dangerous!!

While these deep cycle golf car batteries lasted an exceptional 6.5 years, on a 24/7/365 world cruising boat, I am not a big fan of this many batteries in parallel for this exact reason. This was not my design, wiring or installation, I inherited it. A series/parallel bank would have reduced the number of paralleled batteries that could thermally run away in the event of a cell shorting.

Sadly the marine charging industry has failed us on safely charging parallel batteries by supplying just one battery temp sensor per charger or charge source. A real joke and a travesty. While some do have the option of two temp sensors this is rare.

House load demands are getting larger and larger yet the marine charging industry has done NOTHING to address the safety issues of paralleled batteries such as temp sensor options for each battery..
This is a professional and VERY helpful demonstration, well documented by print shot and photo of true critical situations which facilitates my understanding. Thanks a lot CMS for this great statement !

So, if I understood you correctly, the configuration should be :
- Still my 6 v batteries (for start and service banks) wired in series/parallel.
- At least 1 temp sensor by battery bank. which I don't have yet.

Current configuration aboard is :

- Battery charger : Cristec CPS2 / 12 volts 60 Amperes (no temp sensor). 3 separate outputs with integrated distributor. Each output can be used on its won and supply the entire current.

- Batteries :
- BAT D (2x6v Lifeline AGM GPL-6FT / Amp hour capacity @ 20 Hour rate 300, for engines start bank. Engines are 2x 300 hp Cats 3116 TA .
- BAT 1 (6x6v Varta GC2_3 / 232 Amp (c20) 183 Amp(c5) for service bank.
- BAT 2 (1x12v Varta AGM / 74 Ah 680A for generator Onan 7.5 kW.

- Cristec CSP2 batteries display monitor at lower helm.
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Old 10-13-2016, 03:14 PM   #29
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Originally Posted by Ski in NC View Post
Good point about risk of thermal runaway with paralleled batts with one getting a shorted cell. Seen the havoc from that first hand.
I have had this happen twice, but nothing dramatic.
All batteries I have seem to eventually fail with shorted cells.
Symptoms, they may get warm, and may boil out acid but not enough of a short to explode.
For me, they would run down the parallel battery, but the short must be small enough the DC charger can put in enough power to prevent that.

Last time I discovered when I had the charger off for a few days, and all the batteries disconnected for some work on the battery tray.
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Old 10-13-2016, 03:29 PM   #30
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I'd like to point out we've exceeded the 20 post threshold. These posts have been in series so no anchors have been harmed.
Just for reference, when exceeding the 20 posts, should one use a CQR, Danforth? Exactly which is the preferred anchor for a post-20 post?
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Old 10-13-2016, 04:17 PM   #31
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...what is the good of having 6 x 6v batteries wired in series (actually my service battery bank) instead of 3 x 12v batteries wired in parallel?
Another benefit is that they have a smaller footprint, and sometimes you can fit in more AH in the same space, by arranging them with less wasted space.

For the record, the 6 x 6V are not wired in series. PAIRs of them are wired in series, but the pairs are then wired in parallel.
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Old 10-13-2016, 05:10 PM   #32
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Originally Posted by Pilou View Post
Thanks for clear and precise explanation.
Then if Ah capacity stays the same what is the good of having 6 x 6v batteries wired in series (actually my service battery bank) instead of 3 x 12v batteries wired in parallel?
Deep cycle 6 volt batteries are easy to find because they are used in golf carts. True 12 volt deep cycle batteries are harder to find. And as mentioned above, splitting the batteries in two makes them easier to carry and lift into place.

Other than that, the result is the same.
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Old 10-13-2016, 05:45 PM   #33
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Another benefit is that they have a smaller footprint, and sometimes you can fit in more AH in the same space, by arranging them with less wasted space..
Quote:
Originally Posted by WesK View Post
Deep cycle 6 volt batteries are easy to find because they are used in golf carts. True 12 volt deep cycle batteries are harder to find. And as mentioned above, splitting the batteries in two makes them easier to carry and lift into place.
Other than that, the result is the same.
These are non negligible factors, thank you for that.


Quote:
Originally Posted by CaptTom View Post
For the record, the 6 x 6V are not wired in series. PAIRs of them are wired in series, but the pairs are then wired in parallel.
Thank you for clarifying that as well. It is something more I learned in this thread.

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Old 10-13-2016, 06:03 PM   #34
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Just for reference, when exceeding the 20 posts, should one use a CQR, Danforth? Exactly which is the preferred anchor for a post-20 post?
It's funny !
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Old 10-13-2016, 06:48 PM   #35
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Just for reference, when exceeding the 20 posts, should one use a CQR, Danforth? Exactly which is the preferred anchor for a post-20 post?
Doesn`t matter, provided the thread is securely attached.
Seriously, this is a great educational thread, it doesn`t deserve a limit.
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Old 10-13-2016, 07:58 PM   #36
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My 1977 boat came with 3 built-in 8D battery boxes - 2 8Ds for the house and 1 8D to start both engines. I replaced the house with 6 GCs and gained about 50% AH capacity in the exact same footprint, just a slightly taller profile of an inch or so. If you have 2 8D batts now, it's a worthwhile upgrade on the next replacement cycle.
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Old 10-13-2016, 08:07 PM   #37
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Old 10-13-2016, 08:10 PM   #38
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Old 10-13-2016, 08:39 PM   #39
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Just a point but you should have a charger that puts out 10-15 percent of the battery capacity so a 40 amp charger is not going to do the job unless you are willing to charge for 24+ hours.

I am going to an Inverter/Charger as that seems to be the best way to get a big charger price wise.

Need 100Amp charger and for the price it is a short hop to a combo unit and the cables are darn near the same size.
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Old 10-13-2016, 08:51 PM   #40
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10-15% isn't a hard and fast rule, but an ideal. Sometimes the budget demands otherwise and it's still workable. I went with a 55A IOTA shore charger (~8%) and a Balmar 120A (~15%) alternator deregulated to 100A.

When I relocate, I charge hard. When I run the Honda gen, I charge soft. In the end, it works out just fine. Happy batteries, happy Captain.
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