Batteries: 2X6V or 6X2v

[Momentum M]

Good day guys.  I need to replace my 2X4d's batteries.  I'm in Florida for the Winter and was at the Miami boat show a few weeks ago.  I was inquiring about what was available for replacement and a sales rep, when I asked about the 6V golf cart batteries.....(2X6V in series) X 2 (parallel).  His answer was why not 6 batteries X 2V in series .......that would give me approx. 660ah X6 for a total of 3960Ah!!!! (Here the manufacturer has 4 different model of 2V so depending of the biggest one that would fit in the bench..the Ah will vary).
None the less it's a lot more Ah than 2X4D (approx. 420Ah total) or 2 banks of 6V in series then parallel (depending of model/brand, approx. 300Ah per battery).
Am I missing something ....and I never heard of this arrangement.
Anyone that has more knowledge than me (almost anyone) can comment on this.
I appreciate in advance.
Ps.:  I have a Solbian solar captor (137W/24V+ regulator) and a Balmar 80Amps alternator with a smart regulator.  My draw is similar to every boat  + I have a Dometic Freezer that draws approx. 3.5Ah

Serge

[Dave Spencer]

I've never heard of using 6 x 2V batteries but I suppose anything can be done.  
There is no way you will get 660 x 6 useful Ahrs out of a 2V system though.  If the batteries are 660Ahr at 2 V, then 6 of them in series will yield 660Ahr at 12 V.  (Or, if in parallel, 3960Ahr at 2V)

[Fred Koehlmann]

Hi Serge,

We're looking at replacing our two 4D's as well this spring. Judging that they are both Exide Nautilus Gold NG-4D, they may also have been the original batteries from the previous owner (2002 boat), or maybe they were replaced at some time in between, neither is much consequence to me, since they were such beasties to get out. I've done my own comparison on different batteries and we are targeting four 6volts as the replacement for two main reasons. Weight is one, and I'm not getting stronger with age, unfortunately. Secondly we get more amp/hours per existing battery space. The two 4Ds gave us 160x2=320 A/hr., and I found that the 24, 27 or 31s (I could fit three of each) would give about ~100x3=300 A/hr. The 6volts seem to range between 210 to 260 A/hr, so four would give me ~220x2=440 A/hr (two in series and parallel).  So they give us more capacity relative to the other types.

I did look at the 2 volt batteries, but they are typically much taller and are mostly targeted to the solar industry, such as in off-grid applications. They can have some amazing capacities (Trojan IND33-2V is rated at 1849 A/hr), but you need to have the space for them and I'm such that they're not cheap.

[Steve W10]

Similar situation for me.

Fred, thanks for posting some kind of identification for these batteries.  My searches seemed ineffective for a 2v battery that was appropriate, never mind affordable.

Serge if you have examples of these, please post them.

The batteries I found were huge and priced way out of the average sailor's practicality (prices listed are for individual units, read - multiply by 6!).

http://www.oynot.com/solar-battery-price-list.html
L16RE-2V with Bayonet Cap
Dimensions: 11.67"L,  6.95"W, 17.56"H, Weight 119 lbs.
$365.31

http://www.thesolarbiz.com/Trojan-2V-IND33-Battery-1794-AH
IND33-2V
2 Volts
1794 Amp-hours at the 20 hour rate
Dimensions: 17.334"L x 10.25"W x 24"H
Weight: 278lbs
$855.97

http://www.sbsbattery.com/products-services/by-product/batteries/batteries-flooded-wet-cell-batteries/flooded-wet-cell-batteries-stt-series-flooded-2v-cell.html
STT2V100 (2V110AH)
4.06"L, 8.11"W, 16.14"H
Weight With Electrolyte 29.11 lbs.
Closest thing to pricing I found was with these guys...
http://www.americantechsupply.com/sbsbatteryfloodedwetcellbatteries.htm
They're price sheet from date 12-03 (whatever that means) was...
$132.50

Does not seem like an option to me?

Steve

[Momentum M]

Thanks guys for your reply.  By posting I was trying to find out if any had looked at the 2V AGM (The ones that I saw at the show where from"lifelinebatteries.com").  I had never looked/heard of the 2V.
Also I added the Ah...my mistake here.
Now I'm inclined for the 6V....and I'm still looking around the best one.
Lifeline's GPL-6CT, 90pounds ea., 30Ah.  4 of them would fit in the bench.  They retail between $350/390 ea.
I'm sure that this price is flexible...I'll let you know of the outcome.
Serge 

[Jim Hardesty]

I'll add Rolls batteries.  I looked at them a few years ago.  They had a unique product.  Each cell was individual, then built up for voltage and amperage.  You could replace the cells one at a time (2 volts) and I doubt that each cell would be much over 15#.  They were pricey, but real nice.  Just took a quick look on their web site, didn't see what I remember.  For me the OEM battery set-up works.  They are heavy, used the boom and block and tackle to load them on the boat, then I got them in place by myself.  With 2 think that it would be less difficult.

http://rollsbattery.com/products/18

Jim

[Roc]

Serge & Carole,
If you search this site, you'll find tons of posts on 6 volt golf cart batteries.  I switched to golf cart batts when my (2) 4D's bit the dust.  I bought them at Sam's Club for about $75 a piece.  So a bank of 2 golf cart batts, making 12 volts, ends up being around $150.  This is cheaper than one 4D with more Ahrs.  I've had my set up since 2009. 

[mainesail]

Thanks guys for your reply.  By posting I was trying to find out if any had looked at the 2V AGM (The ones that I saw at the show where from"lifelinebatteries.com").  I had never looked/heard of the 2V.
Also I added the Ah...my mistake here.
Now I'm inclined for the 6V....and I'm still looking around the best one.
Lifeline's GPL-6CT, 90pounds ea., 30Ah.  4 of them would fit in the bench.  They retail between $350/390 ea.
I'm sure that this price is flexible...I'll let you know of the outcome.
Serge 

I don't know if the Lifeline 6CT case would fit, height wise on a C-34, it is 13" tall, but it may. Keep in mind that if you go with 2V cells you must have SIX of them. The 4CT case is 10" tall but you would still need six of them it you went 2V.

Some considerations.

With 2V cells in a series only bank if you lose one cell, you lose the bank.

With 6V is series parallel you can lose one battery and still use the other two.

Lifeline rates their 2V cells at the same cycle life as their 6V cells so no gain there and you must have six of them.

In practice a series only bank can be safer as one battery can't internally short and be driven thermal by the others it is in parallel with. This is really of minimal concern, very rare, and I have only seen this when also connected to a MASSIVE 130A shore inverter/charger. The batteries were also well beyond their useful lifespan and the owner ignored all the warning signs.

If going AGM you will ant to address your charging system so as to get the most life out of them AGM's are very expensive and do not like to sit at anything below 100% SOC for more than a few days.

To properly charge and care for them all charge sources should be temp compensated. These are not like FLA batteries were if you lose some water you put more in. You chronically over charge AGM batteries and they are scrap lead pretty quickly. At anything over 80F battery temp voltage needs to be compensated downwards.

Your alternator & belts also need to be up to the task. Be prepared to "condition charge" (equalize) Lifeline batteries at least once per year (depends upon your use) at 15.5V for approx 8 hours. This is an "attended" type of event to monitor temp of the batteries so plan on about 8 hours +/-.

I would suggest 6V in series or series parallel.. If you can fit the 13" of the 6CT's that great. The 4CT's are the shortest 6V battery on the market and a real gem of a battery. A 600+ Ah bank on a C-34 is pretty big....

[Solstice]

I just spoke with Rolls yesterday. Those 4CT 6V's are 9.92" tall, which would work for me. They are expensive at $320 (per 6V~$640/12V). Maine, wondering if you know of any FLA 'shorties' that would be similar in size to the Lifelines? Although my batteries are still fine, when I replace I would like to do away with the 4D's and even though I've got a good handle on managing AGM's, I may stick with FLA if I can find a 6V 'shortie'...

[mainesail]

Shorty 6V flooded batteries do not exist that I know of. Looked long and hard many times.... Lifeline can get away with a 6V / 220Ah shorty because they don't need the room for the liquid over the cells...

[Mike and Joanne Stimmler]

I still think the best bang for the buck is the Costco or Sams Club 6V golf cart batteries.

[Stu Jackson]

I still think the best bang for the buck is the Costco or Sams Club 6V golf cart batteries.

Mike's right.

Gentlemen and Ladies:

This issue has been discussed to exhaustion.

AGMs make NO sense for weekenders.  They require complete charging, always.

Plugging in all the time makes little sense.

6V makes a LOT of sense and they DO FIT in the C34 battery box.  Find another place for a reserve bank if you choose to do so.  There are about four places for one.

FLA are GREAT choices.

4Ds are NOT.  Ever.

Check the wiki.  It's all there.

Good luck.