4 six volts better than 2 twelve volts

[ranger58sb]

Originally Posted by rsn48

Was talking to a chap and told him of my possible battery acquisitions. He recommended I get 4 six volts, two wired in parallel, rather than 2 twelve volts. He said the 6 volt jobbies were better as part of battery function was dependent on size and the two 6 volts would offer more usage than an equivalent one 12 volt. Checking to see if this is true.

Presume you mean for house functions? To which 12V batteries would you compare? And what means "better?"

Four 6V GC2 in series/parallel would give you about 440 Ah capacity (220x2) at 12V.

Two 12V G31s (for example) would give you about 100 Ah capacity. Two 12V 8Ds would give you about 490 Ah capacity.

Better = more capacity? Four GC2s would be "better" than two G31s, but not as good as some 8Ds.

Better = possibly more longevity? Most GC2s are true deep cycle batteries, whereas most 12V options are really dual-purpose batteries even when labeled "deep cycle." (There are exceptions.)

Better = easier to install? Each individual GC2 would likely weigh about the same as a decent G31, maybe half (?) the weight of an 8D.

Note that if a single 12V battery goes south in a 12V bank, you can rewire to get home. Similarly if a single GC2 goes south in a bank of four, you can temporarily rewire to a 12V bank that could get you home. That last doesn't work so much in a bank of two GC2s.

If you did NOT mean house functions, then the analysis needs to consider CCAs and MCAs more than capacity. OTOH, I suspect most pairs of GC2s will start most sailboat engines...

-Chris

[Boatyarddog]

Just a note to consider.
Trojan T-104s weigh around 80 lbs per cell.
So, when considering where to install those lunkers,
4x80=320lbs
If your sailing a 28', consider the amount of list you may encounter.
That's a lot of reserve though, for your house bank.

[stormalong]

Originally Posted by 01kiwijohn

Yes, the 4 6v will provide better service as a house bank however, on your boat you should be able to get the job done with 2 6v deep cycle.

That all depends on how you use your boat. Keep in mind that for optimum life you should not discharge your batteries more that 50%.

With refrigerator, separate freezer, electric autopilot and a whole bunch of electronic goodies two six volters won't do it. I have had six of them for my cruising life. Now that I only do coastal four are enough.

[Sailorlou]

Here is an example of six 6 volt batteries properly wired.
https://www.sailblogs.com/member/far.../41274/859186/

[MrWesson]

Better as house batteries(like we need) you bet..

Some applications call for high Cold Crank Amps VS overall AH and think twice before replacing your car battery with golf cart batts.

[GrowleyMonster]

Originally Posted by S/V Alchemy

You tell me. As long as you can manage the correct wiring and be sensitive to load balancing and keeping the interconnections the same length, you can have a huge, reliable bank at little cost. This is 1185 Ah at 12VDC nominal. This is on the centerline, under the mast and under the saloon stairs, about as good a hidey hole as is possible on a 40 footer:

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.

[_andi_]

just to add another point of view:


The less batteries, the less trouble with balancing, corrosion, refill, terminal fuses, ...


Nowadays there are decent 12V deep cycle accumulators, I ended up buying Exide Equipment Gel, on the euro market only a bit more expensive than wet trojans. Upside: robust, can be installed at an incline and they come back to live even if completely discharged.

[john61ct]

If you want GEL, go for Sonnenschein

[john61ct]

Parallel is fine up to 3 strings maybe 4.

Much better for many reasons to have just one big House bank, not splitting up for dedicated functions unless **really** no other choice.

[john61ct]

Originally Posted by Lost Horizons

The statement above is false.



The only difference is that each 6V battery will be lighter and easier to handle than the 12V unit. If that is desirable, 6 2V cells would be even better. Also, will eliminate a parallel connection (of 2 12V units), which will potentially extend battery life and increasy effective capacity.

No, the inherent design and build quality is what's being discussed, for deep cycling use.

To get the same longevity in 12V requires very expensive specialized brands like Rolls Surette.

6V GC FLA from Deka, Trojan, Crown, U.S. Battery Superior are readily available locally in most of NA and cheap as chips compared to quality 12V.

[john61ct]

AGM are much more expensive per AH, much fussier in care requirements and less robust, even coddled don't last as long.

Forklift use case assumes all night charging.

Trojan doesn't make quality AGM anyway, unlike their great FLA.

[_andi_]

Originally Posted by john61ct

If you want GEL, go for Sonnenschein

... which is an exide brand.

[CarinaPDX]

An amusing thread... The "best" battery is a function of what you value most. If it is bang-for-the-buck and longevity, assuming willingness to maintain them, then 6V FLA golf cart batteries win hands down. If simplicity and durability is the goal, and money is less important, then go for 12V Rolls/Surrette FLA batteries. But if the goal is to reduce charge time (and hence hours on the engine) then use AGM or gel batteries; the same if topping up the electrolyte every month is too big a nuisance. They also provide a stiffer voltage (less voltage sag under load). And if you must have the latest, bleeding edge technology then go for lithiums, which will have high energy density and faster charging among other advantages, at a very high price.

"Best" is a pretty fuzzy concept; quality isn't. Whichever technology is used don't skimp on quality. Always go with quality brands if you plan on keeping the boat long. And invest in quality charging systems (battery chargers, alternator regulators, solar regulators, etc) as they will have a lot to do with battery longevity.

Greg

[KP44]

Originally Posted by CaptainJohn49

This brings up an important point. AGM's require less service. Seem to take abuse better. Can be mounted anywhere even of their side. Don't boil over. Don't loose water (they are a mat internally). Will continue to work if the case is damaged. Don't seem to have corrosion at the terminals. They DO COST more but I have gotten much longer service life.

I need to speak up here.

I am replacing my three 8D AGM batteries with eight 6 volt in series parallel. I used 6 volt before and they did well for 10 years.
I replaced with the 3 expensive AGMs (About $2,000, if I remember right.) and they gave me a smaller battery bank and nothing but problems. They did not seem to actually give the amp hours they were rated at. I have a 150 amp Ample Power alternator and an advanced Balmar regulator. The AGMs never seemed to have the storage they were rated at. (West Marine batteries.)
After a dismal season last year, I bought 8 new 6-volts to replace the AGMs. When I pulled them out, I found the sealed AGMs that "never leak and never boil over" had leaked and crumbled the floor beneath them. I cut out the acid-crumbled area yesterday and am replacing it.
I always used (home-made) battery boxes with the 6 volts. But since the AGMs are "sealed and never leak or give any problems", I strapped them directly to the floor. Big mistake; they do leak. I saw leakage down the sides of two of the three AGMs.
So I will be back up to about a 900 amp hour bank for half the cost of the undependable AGMs.
Just thought I need to share this.

[CarinaPDX]

Something about "quality". If I were buying AGMs I would limit the search to Lifeline, who have a sterling reputation. West Marine? I don"t know who is making them but probably not Lifeline.

Both AGM and gel batteries can and do vent if overcharged, which also results in internal damage. Before blaming the AGM technology I would want to know a lot more about your charging system and its settings. FLA is much more tolerant of high voltages. All charge regulators (AC battery charger, alternator regulator, solar/wind regulators) need to have the appropriate settings for absorption charge voltage, time at absorption or current trip, and float voltage. Not floating, too high an absorption voltage or too long in absorption can ruin AGMs and gels. I'm not saying that is the cause in this case, but that is where I would start looking...

Greg