Battery question

GordonThree,

Why do you not like LiFePO4?

GordonThree wrote:
I was marveling at some cells designed for forklifts, 8ah per cell rated for 200a continuous discharge. They were LiFePO4 chemistry though, which I'm not crazy about.

pianotuna wrote:
GordonThree

Hmmm $2 per amp-hour for LI. Current pricing is only 5 times that amount.

It's getting closer in the DIY realm.

I was marveling at some cells designed for forklifts, 8ah per cell rated for 200a continuous discharge. They were LiFePO4 chemistry though, which I'm not crazy about.

3 tons wrote:

Two 6v wired in series is essentially one BIG 12v battery, so your inverter won’t know the difference... Remember that when the voltage doubles from 6 to 12v, the amp hours are cut in half...Generally speaking, 6v GC’s (golf cart) have a deeper depth of discharge (DOD) than 12v automotive starting batteries, thus more ‘usable’ amp hour ...

Absolutely !

True "deep discharge" 12V batteries are difficult to find and cost at lot of $$$. Costco or Sams has golf cart batteries (size GC2) for about $90 a piece.

GordonThree

Well said.

Hmmm $2 per amp-hour for LI. Current pricing is only 5 times that amount.

GordonThree wrote:
Series 6v go deeper, parallel 12v push harder

Choose based on usage?

I'll be a happy man when I can buy a lithium nickle manganese cobalt (NMC) based "12v" battery with built in BMS for under $2 per amp-hour

RV BATTERIES = 100 meter dash. Retires at age 22

TRUE CYCLABLE BATTERIES = 20Km marathon. Retires at age 50

Of course, you can't do ONE 6V battery.

You already have One 12V battery. If that isn't enough and you have room:

Then, TWO 6V batteries

Not Two 12V batteries. The advantage, of course, is that if one 12V goes bad, you can still use the other. The problem is, two 12's don't seem to play as well together as two 6's do. So in theory you have redundancy with two 12's, but in practicality, you're more likely to have both 12's go bad, than with a pair of 6's.

3 tons wrote:

jalichty wrote:
My batteries are reaching the end of their good useful life and I am wondering whether to replace them with two 6 volt rather than two 12 volt ones? Would I have to change my inverter, I have a 2012 Jayco HT with no plans to get rid of it. Would the 6 volt ones give me a bit more reserve and more re-charges, are they worth the additional money? I have no plans on going solar, just wanting help with this decision.

Two 6v wired in series is essentially one BIG 12v battery, so your inverter won’t know the difference... Remember that when the voltage doubles from 6 to 12v, the amp hours are cut in half...Generally speaking, 6v GC’s (golf cart) have a deeper depth of discharge (DOD) than 12v automotive starting batteries, thus more ‘usable’ amp hours with the same size foot print, though they are about 3/4” taller... Per other threads, some manufactures offer ‘true’ 12v deep cycle batteries, but be advised that some that are available are advertised as deep cycle but are really of a hybrid engine starting type...

Two six volts in series are not just essentially a big 12V battery, they precisely form a 12V battery.

The Ah aren't really halved, they just don't add the way they do for batteries in parallel. It's clearer if you think in terms of energy storage rather than charge storage, which is to say watt-hours rather than amp-hours. In that case, the energy storage does go up in either case; you're adding energy.

As to what setup is preferable, in general for many people the dual 6V golf cart batteries offer the best bang for the buck if one needs more than a single 12V battery. No change would be required for your inverter or converter.

Series 6v go deeper, parallel 12v push harder

Choose based on usage?