Why 6 volt vs 2 12 volt

[CurtPutnam]

I have read numerous threads about 2 x6 vdc batteries being "better" the same in 12 vdc. I believe. I've done it. But what is the advantage? Why?

TIA

[Duckogram]

Higher Capacity

[bikendan]

6v golf cart batteries have thicker and longer-lasting plates. They also have higher ratings.
And a true 12v deep cycle battery is not common. Most are dual purpose marine batteries, which are less capable. They have CCA ratings which is for starting engines.

[CurtPutnam]

Originally Posted by bikendan

6v golf cart batteries have thicker and longer-lasting plates. They also have higher ratings.
And a true 12v deep cycle battery is not common. Most are dual purpose marine batteries, which are less capable. They have CCA ratings which is for starting engines.

Thank you. What I think you are saying is that size for size, 6 volt batts will put out more amp-hours for longer?

[Duckogram]

Exactly the gist of it. However amp/hr ratings can be a bit of a shell game.

[kcmusa]

But there are company's that make great 12v deep cycle batterys
https://www.trojanbattery.com/product/t-1275/

[SeaDog]

Something no one ever talks about is with the 2 6V batteries if a cell goes bad you loose 12V power, where as with 2 12V batteries if you have a cell go bad in one battery you can remove the battery and still have 12V to operate.

[67L48]

Just remember, 2 batteries in series doubles the potential and not the capacity. 2 batteries in parallel doubles the capacity and not the potential.

So, grab two 6 VDC, 220 A-Hr batteries, put them in series, and you have a 12 VDC power supply with 220 A-Hr of capacity.

Grab two 12 VDC 120 A-Hr batteries, put them in parallel, and you have a 12 VDC power supply with 240 A-Hr of capacity.

The 6 VDC batteries independently have more capacity than a 12 VDC battery. However, in a 2x battery pack, the capacity will be pretty similar when using group 29 and larger 12 VDC. 6 VDC batteries are also more durable and reliable ... will withstand more discharge/charge cycles than their weaker 12 VDC counterparts.

A Trojan T-105 will give about 225 Amp-Hours. A group 29 battery from Advanced Auto Parts will give me about 115 Amp-Hours (both using a 20 hour discharge rate). So, the 2-battery systems will have similar capacities. Trojan will be much more durable ... and about twice as expensive.

Good luck.

[aeblank]

More or less, buy wet batteries by the pound. The heavier, the more amps.

[Duckogram]

Originally Posted by SeaDog

Something no one ever talks about is with the 2 6V batteries if a cell goes bad you loose 12V power, where as with 2 12V batteries if you have a cell go bad in one battery you can remove the battery and still have 12V to operate.

Thats a good point. So it’s 4 each 6V Batteries, A Ford, Goodyear Tires all torqued down to 1500 ft/lb with more memory than the Pentagon. So lets go RV’ing.

Vaya Con Dios

[jtesta1]

More plate surface in two batteries. Will increase potential power.

[babock]

There really is no difference using 2 12V batteries in parallel vs 2 6V in series if you are comparing the same brand and chemistry of batteries. For example, 2 Trojan deep cell will perform equally whether they are 6V or 12V. The plate size that everyone talks about is internet lore that gets perpetuated.

When I worked on the GM EV1 way back in my career, we used 12V flooded lead acid. If it was actually better to use 6Vs performance wise, we would have.

The reason people use 6V golf cart batteries for RVs is that it's usually cheaper when comparing AH to AH. That's the only reason.

[timfromma]

I have a pair of these mounted on my trailer tongue:


https://www.westmarine.com/buy/west-...4?recordNum=12

[NMWildcat]

Originally Posted by babock

There really is no difference using 2 12V batteries in parallel vs 2 6V in series if you are comparing the same brand and chemistry of batteries. For example, 2 Trojan deep cell will perform equally whether they are 6V or 12V. The plate size that everyone talks about is internet lore that gets perpetuated.

When I worked on the GM EV1 way back in my career, we used 12V flooded lead acid. If it was actually better to use 6Vs performance wise, we would have.

The reason people use 6V golf cart batteries for RVs is that it's usually cheaper when comparing AH to AH. That's the only reason.

Exactly! Thank you.

[Larry-NC]

Originally Posted by CurtPutnam

Thank you. What I think you are saying is that size for size, 6 volt batts will put out more amp-hours for longer?

And...the 6 volt golf-cart batteries will withstand many more deep discharge cycles without damage than common 12 volt batteries.

Larry

[camaraderie]

Let compare apples to apples.
The pair of 6Volt golf cart batteries generally will provide about 210 amp hours when hooked up to provide 12V.
A pair of TRUE deep cycle 12V batteries in group31 size will provide roughly the SAME amp hours.



BOTH will have good thick plates which are designed to LAST under deep cycle use though hundreds more cycles than thinner plate dual purpose or really thin plate starting batteries which are both designed to provide HIGHER instantaneous current (for starting use) while giving SIMILAR amp hours in total BUT not lasting nearly as long in cycle life.



YES it is not as easy to find TRUE DEEP cycle 12volt batteries as it is to find golf carts at Sams Club etc. AND they are generally more expensive per amp hour rating.
BUT they MAY be built more ruggedly than the 6volt cheapos and they may also be built to deliver more lifetime cycles. AND of course they may be operated as single 12V batteries if one fails.
(You should have a battery monitor if you hope to notice such a single failure before both fail!)


My own view is that 6V is best used in quantities of 4 or more...but if you only have room for 2 and you boondock...get a Trojan or DC series Deka true deep cycle pair of 12V. For longer cycle life and better failure options.
If you don't deep cycle (boondock)..dual purpose batts are cheap at walmart and fine.

On a pure cost per amp hour delivered over a normal lifetime of deep cycles...it is hard to beat the warehouse club 6Volt pricing.


Of course...we are talking about wet cells here.
There AGM, TPPL/AGM, CarbonFoam and Lithium LiFePo4 options at much higher initial prices and each makes sense for some folks. But that is a discussion for another thread!

[aircommuter]

The person who said plate surface area had it correct as far as output goes. 6v batteries are designed for industrial applications where more height is available, 12v are generally designed around vehicle applications where low profile is often desirable. When it comes to plate thickness it depends on the make and model, Trojan and Deka are considered the low end of solar batteries, Rolls Surette, Concorde and some others have plates that are up to twice as thick.

[babock]

Originally Posted by Larry-NC

And...the 6 volt golf-cart batteries will withstand many more deep discharge cycles without damage than common 12 volt batteries.

Larry

While this is true for common 12V, true deep discharge 12Vs can withstand the exact discharges.

[CurtPutnam]

OK, now we are getting to why I asked the question. It seems logical that 6v and 12v batteries of identical construction, identical plate size and chemistry with identical amp-hour ratings should perform equally. Correct assumption?

[babock]

Originally Posted by CurtPutnam

OK, now we are getting to why I asked the question. It seems logical that 6v and 12v batteries of identical construction, identical plate size and chemistry with identical amp-hour ratings should perform equally. Correct assumption?

Yep..exactly as I have already stated a number of times.