re 12v vs 6v Batteries

Jawsinparadise wrote:
Extremely strange to read all the opinions re this subject. Most written by author "OLDMAN"
I purchased my new Wildwood last month. The contact person that did the paperwork was a "OLDMAN".
In my contract I was to have 2 batteries. What was installed were 2 6v in series. I wanted 2 12v in parallel. Twice the ccp as 2 6v. If one 12v fails you have another. If one six fails you have nothing.
How one assumes 2 6v are equal or better than 2 12v has little knowledge how batteries are rated in series or parallel.

Troll who joined a week ago, already snarking. This forum needs more snarking. Good job OP.

Btw, most here would be thrilled the dealer installed 2 6v in lieu of 2 standard grp 24 batteries in parallel. It is considered an upgrade that many pay additional for. I'm sure, if you complained loud enough, your dealer would be more than happy to trade your two 6v for 2 grp 24 12V batteries. Knock yourself out. Your rv, your choice.

Ok, I'll play nice.

Gman

wa8yxm wrote:

ktmrfs wrote:

renoman69 wrote:
You are WAY better off with 2 6 volts batts and no I won't explain why. Just trust me.

for many applications I agree. There is one that I believe 12V will be better. That application is when the dominant use is with a high power inverter (1KW and up) or other constant high current draw (>50-75A). Then 12V banks are IMHO a better choice. They offer low voltage drop with high current, and with more banks for the AH needed, each bank is also supplying lower current.

But if your draw is more like most 12V appliance draws then yes 6V is the way to go, even if you occasional have a high current draw.

I disagree.. You take a pair of six volt 225 amp hour batteries and draw say 100 amps off them, that is 2/5ths (40%) of their 20 hour rating, (Of course modern six volt are 230 but I'll stick with 225 for now cause that's what mine are. (older)

You get say two Group 29's, roughly 100 amp hours each and while it is true that each battery is only providing 50 amps that is a full FIFTY PERCENT (1/2) of their 20 hour rating. So again the six volt win

Group 31's. you have a total of about 260 Amp hours. But only just a bit better.. 5/13ths of the total capacity..

But Group 31's won't fit in the same tray.

Though that said: Starting batteries are designed to deliver amprage that EXCEEDS their 20 hour rate, That is a single Group 24 can easily deliver more than 150 amps (2x it's 20 hour rating) for a short period of time.

But it can also only deliver about 20-25 percent of that power before it begain to suffer big time, where as the six volt pair can deliver half their power before they really need a recharge.

It isn't the AH that is the issue with high current draw, it is the internal voltage drop on the cells that poses a problem. 6V have noticeably higher internal resistance, and for the same AH capacity double or more the current/cell that a 12V bank will have. Based on personal experience, trying to power a 1000W load (80-100A) from a pair of Golf carts for an inverter works if the 6V bank is charged to 75-80% or more. much below that and the internal voltage drop hits the cuttoff. Not necessarily so with "equavalent" 12V bank. First 12V will have lower drop, second for a 200AH bank, you'll have at least two 12V so each one is only delivering 40A or so vs the 80A of a GC pair. Much less internal drop so you can run an inverter at a lower SOC.


And for things like a microwave, usually your looking for a few minutes of run time at most, so it isn't as much AH as amps that is the big need.

Others with GC and big inverter loads have had similar results.

And it only gets worse if you try to power say a 2000W inverter from a pair of GC vs. 12V. 200A REALLY sags a pair of GC.

Now, since we only occasionally use the microwave when on battey power the GC bank is still the best choice for overall battery life and battery run time. And that is probably the case for most of the folks on this board. But if your load is constantly high current then 12V deserves consideration.

I found this this site its probably for beginners so it helped me any thing y'all can add to it for me or are these pretty good rules. Thankshttp://www.windsun.com/Batteries/Battery_FAQ.htm#Using%20a%20deep%20cycle%20battery%20as%20a%20starting%20battery

wa8yxm wrote:
Actually the Six volt deep cycle do not so bad as starting batteryes, The starting battery in my RV is around 80 amp hour. The six volt pair 220 (older) so a 160 amp load is 2x the amp hour capacity for the cranking battrey but only about 3/4 of the capacity on the deep cycles, NOT a heavy load at all.

And that's the crankey battery for an 8.1L Vortec V-8,, As for the Onan, I've crenked it with a 27 amp hour AGM

Ah across different battery types does not have much to do with cranking capacity though, and AGMs tend to crank really well, even the small ones. I crank a high compression race car with a 32 Ah AGM.

Jim

Jawsinparadise wrote:
Extremely strange to read all the opinions re this subject. Most written by author "OLDMAN"
How one assumes 2 6v are equal or better than 2 12v has little knowledge how batteries are rated in series or parallel.

That's what a discussion board is about.. opinions.

What gives you the impression I wrote it?

Actually the Six volt deep cycle do not so bad as starting batteryes, The starting battery in my RV is around 80 amp hour. The six volt pair 220 (older) so a 160 amp load is 2x the amp hour capacity for the cranking battrey but only about 3/4 of the capacity on the deep cycles, NOT a heavy load at all.

And that's the crankey battery for an 8.1L Vortec V-8,, As for the Onan, I've crenked it with a 27 amp hour AGM

The 6v deep cycles will have fewer CCAs, but plenty to start a genset even if it is cold out, especially Texas cold vs say Alberta cold.

Jim

Well I'm reading all of this trying to understand batteries better i don't even know what a amp hr is yet. I understand the 2 6 volt bat will last longer than the 1 12 v bat but the 12v has more cranking amps . If the 12 v had 750 cca and a 100 amp hr and the 2 6 v had 225 amp hr how many cca amps would the 2 have would it start a generator in real cold weather.thanks

" There is a reason that engineered systems always use battery cells in series not in parallel"

Pray tell, is that kind of preferred system "engineered" to replicate the old Christmas tree light-string effect? When one bulb fails the rest become useless?

Series or parallel is a giant compromise due mainly to room or money or both. I.E. a series/parallel system will have fewer catastrophic effect failures.

There is a reason that engineered systems always use battery cells in series not in parallel.

Your RV is better off with all battery cells in series. Then you just need big enough cells for the capacity you want (since we are limited to 12 volt systems we have to increase the cell size to increase capacity and cannot increase voltage instead).

Since we have practical limits to the battery cells we can use (6v batteries have three cells and 12v batteries have 6 cells, BTW) we are often forced to compromise. For overall performance, as stated by so many here, the 6v CG batteries offer the best value and performance for an RV battery system.