What is the best way to configure 12 volt batteries for a 24 volt bank?

[Xan]

If one has, say four, 12 volt batteries and wishes to connect them to form a 24 volt battery bank there are two main basic connection schemes as shown on my (roughly drawn) diagram.

Configuration 'A' is what could be called "parallel / series" while Configuration 'B' is definitely "series / parallel" in my view.

The question is: Which one of these configurations is the better one to use and why? 

[Mary B]

I would say b... more balanced for charging

[Flux]

B is the normal method and is well balanced, both parallel path lengths are equal.

A as it stands is not good. It could be improved a lot, but tricky to explain without a drawing. Basically you move the output negative to lower right battery and make the series connection as a diagonal to equalise lengths.

In view of the fact that B is entirely satisfactory it's probably best to stick with that rather than risk confusion.

Flux

[Mary B]

B is probably lowest resistance overall with less wire...

[kitestrings]

Many folks like to have the batteries all facing the same way, to avoid confusion, and then wire between them.  I prefer to alternate them 180 degrees within each series string - this is what you have in "B" - it makes for shorter jumpers.

In your sketch the batteries in each series string are nearly a battery length apart; and half that in parallel.  In practice they can be much closer, though best to have some space for visibility and consistent temperatures.

~ks

[heybobc]

A general problem with batteries in parallel is that no two batteries are the same. That means one will take more of the charge, and one will supply more to the load than the other. That said, in 'B' you are possibly doubling that effect. Whether that is something to think (worry?) about, I'm not sure.

Bob