4 six volts better than 2 twelve volts

[john61ct]

Originally Posted by fish53

There are no "exceptions"

Sorry you're just wrong.

The internal plate design is a factor, but not all are the same.

The key factor is true real-life deep cycling lifetime, usually using 50% DoD as a benchmark.

GCs from the vendors I named, including Trojan and Deka, perform well.

Interstates does not make any batteries, but likely JCI, and they do not.

[GrowleyMonster]

Originally Posted by sailorboy1

Isn’t it amazing that this topic comes up almost monthly and still gets the same responses mostly from the same people as it got the last 6+ times.

You're right. I think I will join the "golf cart batteries are crap" camp LOL.

[fish53]

Originally Posted by john61ct

Sorry you're just wrong.

The internal plate design is a factor, but not all are the same.

The key factor is true real-life deep cycling lifetime, usually using 50% DoD as a benchmark.

GCs from the vendors I named, including Trojan and Deka, perform well.

Interstates does not make any batteries, but likely JCI, and they do not.

Well as there is no universally agreed on definition for what a "deep cycle" battery actually is it's very hard for either of us to be wrong. In my opinion a golf cart battery isn't a true deep cycle battery yet I will concede they are albeit a very poor one.

[valhalla360]

Originally Posted by hooligan6a

Two 6 volts are fine until one cell goes bad and then you no longer have 12 volts.
if you have 2- 12 volts and one cell goes bad you still have 12 volts. You can't start an engine on 6 volts

If he has 4 - 6V, he can still make 12v for starting the engine. In fact, he can have 2 batteries fail and still make 12v.

To the original question: If they are equivalent batteries, 12v are better.

But in real life they aren't equivalent:
- The vast majority of 12v batteries you can find are starting batteries not well suited to deep cycle use (even those listed as dual purpose or trolling motor batteries).
- There are a few true deep cycle 12v batteries but they are incredibly expensive...but even if expense is not an issue, sourcing a replacement battery would be more hassle than it's worth.
- Also, you have to compare amp-hr ratings at 12v to compare...two typical 12v batteries are roughly the same size as two 6v batteries...and as you can expect the total amp-hr at 12v will be less than four 6v batteries.

[john61ct]

Originally Posted by fish53

Well as there is no universally agreed on definition for what a "deep cycle" battery actually is it's very hard for either of us to be wrong. In my opinion a golf cart battery isn't a true deep cycle battery yet I will concede they are albeit a very poor one.

For me, it's 600-800 cycles lifetime rating from a trusted mfg, backed up by thousands of members in sailing & high-end RV forum reports.

Rolls/Surette, Trojan, Deka/East Penn, U.S. Battery, Crown and Superior

For NA market, that is all.

The best battery **value** by far is Duracell (actually Deka/East Penn) FLA deep cycle golf cart batteries, 2x6V, around $200 per 200+AH @12V pair from BatteriesPlus or Sam's Club.

Deka labeled same batts also sold at Lowes.

Nice thing about such cheap batts available is someone that hasn't mastered all the knowledge & tools required to get 6-10 years from their bank, is not out a lot of money if they murder them within 2-3.

Their spending money on the likes of Rolls would not be wise.

Spending the extra money once you can coddle them is worth it for those with mission-critical needs, full-time boondocking in primitive locations, etc.

[OldMan]

Originally Posted by john61ct

For me, it's 600-800 cycles lifetime rating from a trusted mfg, backed up by thousands of members in sailing & high-end RV forum reports.

Rolls/Surette, Trojan, Deka/East Penn, U.S. Battery, Crown and Superior

For NA market, that is all.

The best battery **value** by far is Duracell (actually Deka/East Penn) FLA deep cycle golf cart batteries, 2x6V, around $200 per 200+AH @12V pair from BatteriesPlus or Sam's Club.

Deka labeled same batts also sold at Lowes.

Nice thing about such cheap batts available is someone that hasn't mastered all the knowledge & tools required to get 6-10 years from their bank, is not out a lot of money if they murder them within 2-3.

Their spending money on the likes of Rolls would not be wise.

Spending the extra money once you can coddle them is worth it for those with mission-critical needs, full-time boondocking in primitive locations, etc.

Trojan's T-105's are cheap in South Florida.... ~$87 each.

[S/V Alchemy]

Originally Posted by stormalong

Six golf cart batteries is more like 600 amp hours at 12 volts. Sorry to burst your bubble but when there are two batteries in series the amp hours are not added together. Unless there are another six batteries not shown in your photograph you have half the AH you think you have,

Those batteries are rated at the customary 20 hour rate at 395 Ah each in the 122 lb/per. L-16 format, not the GC2 "golf cart" format. In series, that's 2370 Ah @ a nominal 6 VDC or 1185Ah in series/parallel at a nominal 12 VDC. They are kept generally at 75%-100% SOC by a Victron MultiPlus 3000 Kva charger/inverter. The bank is the size it is for reasons of internal ballast as well as wanting to cycle within a far narrow range than most boats in order to get maximum duty cycles.

I have the Ah stated, because you cannot see they are L-16s and assumed, incorrectly, that you were looking at golf cart batts. These are actually made for solar power and/or forklifts/floor sweeping machines. They do quite well in the middle of my boat.

[S/V Alchemy]

Originally Posted by GrowleyMonster

So those are 395ah batteries? Oh I see handles. Must be L-16 or similar. Nice setup. I still don't like parallel unless I can quickly isolate. Cells do go bad. Me, if I had those batteries given to me, my own personal preference would be to split into three banks. Two primary twin banks on an A/B/All switch, one forward for windlass, bow thruster, etc. Or maybe engine starting. Switchable configuration.



You have a nice symmetrical layout, very good matching of interconnect lengths, but I dont see any fuses. Me, I would fuse the positive of each battery at maybe 200a. Nobody sez you got to, though.

Thanks. I took some time to get that right, and the FTZ crimper and properly tinned power lugs helped a lot. This is prior to the charger going in. There's a 400 amp T-fuse on 4/0 ga. wire running to that and 600 amp-rated shut-offs on both the positive and the negative sides. Monitoring is via a negative side shunt. Cabling to busbars and engine is all 2/0 ga. and is 1 ga. to panels.

It all works pretty well. I currently start the diesel off the house bank, but as I wire in shore-independent charging sources (solar panels, wind gen and a couple of Hondas), I am thinking of a standalone 12 VDC battery to be charged from the house bank via ACR and switchable should I need to work on the house bank and still want DC power available.

[roland stockham]

Simple answer is that there are very few 12v deep cycle batteries made (as far as I know none) whatever is says on the box. Generally if it is 12v it is at best a heavy duty cranking battery. Expect around 1/3 the service life you would get from a decent 6v one. With sealed lead acid this is less of an issue as they are ALL short service life and are dead if they run low on water for any reason.

[Adelie]

I got a Trojan T-1275 which is a 12v battery. All the literature from them says Deep cycle, it is listed with the golf cart batteries and not the industrial starting batteries.

[FlyingScot]

This should be required reading. From fellow CF member.
https://marinehowto.com/what-is-a-deep-cycle-battery/

[john61ct]

Originally Posted by OldMan

Trojan's T-105's are cheap in South Florida.... ~$87 each.

Great! I personally think Deka's are just as good, but if T105s are in the same ballpark, get them!

Warranty policy of the seller is worth some consideration, but very rarely needed if caring for them properly.

[fish53]

Originally Posted by FlyingScot

This should be required reading. From fellow CF member.
https://marinehowto.com/what-is-a-deep-cycle-battery/

Good article, thank you.

[john61ct]

Originally Posted by roland stockham

as far as I know none

In FLA Rolls are the exception.

> whatever is says on the box
Yes lots of fraudulent labelling, especially big box retail and automotive

In AGM, Odyssey, Lifeline and Northstar make some great 12V deep cycling batts.

lots pricier and not as robust as FLA though, but sometimes you need to install sideways, or can't easily get to the bank for watering

At lower SoC, AGM also accept faster charging rates, but still take 6-7 hours when you want to get to 100% Full.

[john61ct]

Originally Posted by Adelie

I got a Trojan T-1275 which is a 12v battery. All the literature from them says Deep cycle, it is listed with the golf cart batteries and not the industrial starting batteries.

Yes, their J150 as well.

Besides trusting the maker, non-automotive sizes are a positive indicator.