4 x 12 v battery arrangements

[Possum]

Hi there.

We currently run two separate off grid setups.
Each uses two 12 v batteries.
one is at 12 volt
the other is 24 volt

the 24 volt bank runs a 24v inverter. But now we want to combine all four batteries (i understand this is not such a great idea considering age) into one 24v bank.

Is the only way to achieve this a series and parallel setup?

[Mike90250]

Yes, you would wire all 4 batteries into a 2S 2P arrangement, knowing in advance you are mixing unequal batteries and they will fail sooner.

Be sure all batteries are fully charged and very close to the same voltage before you connect, otherwise, the fuller battery, will rapidly discharge in to the lesser battery