Mixing different AH batteries in your setup.

[luthj]

Yeah, thats not ideal, especially with a 100A load thrown in. It can be done, but be aware you are cutting the cycle life of the batteries by about 20-30%. Now, you can do the math. If you ran with just the 200AH pair, you would get X amount of life. the smaller battery has about Y life. Putting the other battery in parallel would be something like (X+Y)*0.8, would it be cheaper to go with another matched bank? Or does it make financial sense to stick with what youve got, and take the hit in overall life?

Also, are the batteries mounted near each other, with balanced wiring? If they are mounted far apart, you really need to pay attention to balancing.

 

[dreadlocks]

one is 6v the other is 12v, there's no guarantee both have identical cells within (they probably dont because 6v cells are bigger than 12v ones).. those are some hella expensive batteries to not do right..

Sounds like you should put the 12v in as a separate bank, put a transfer switch on your loads and keep that one as a reserve battery you can flip over too.. its going to need to be connected during charging inputs so it stays maintained.
Either that, or your at your holding capacity, next time buy 3x12v in parallel with an odd number setup such as yours.

 

[Jonnyo]

one is 6v the other is 12v, there's no guarantee both have identical cells within.. those are some hella expensive batteries to not do right..

Sounds like you should put the 12v in as a separate bank, put a transfer switch on your loads and keep that one as a reserve battery you can flip over too.. its going to need to be connected during charging inputs so it stays maintained.
Either that, or your at your holding capacity, next time buy 3x12v in parallel with an odd number setup such as yours.

i have no gotten the 12v yet... i only currently have the 2X6v. i m in canada so those battery are not expensive like they can be anywhere else! But i do realise they are great battery! Anyway, i always though in paralelle, it wasnt a much of a issue to mix difference capacity battery as long as they are the same chemistry. Perhaps if i really want to increase my battery bank, i better go for another 2X 6v identical to the first set.

i see how 3X12v would had been ideal with the space i have in the compartment.

 

[john61ct]

If I were a nearly-homeless car camper making do with donated secondhand batteries, then I'd make do with a set of mismatched components.

If I could afford say eating food prepared by others, I'd save my pennies, rework the installation space, whatever, so My bank would be composed of identical cells with the same mfg date.