To Parallel Or Not To Parallel

To parallel or not to parallel, this is the question..

What are your opinions on:

1. Is it 'suitable' to parallel two batteries of the same voltage?

2. Is it 'suitable' to parallel two batteries of differing voltage?
(I do believe this to be unsuitable, but what are your opinions)

Dear Scuzz

I think you should apply to parallel two batteries of the same voltage !

Thank you !

I'm pretty sure it's ok to parallel batterys of the same voltage, but of differing voltages, I don't think so. I suspect it will have a effect very similar to the battery with the higher voltage trying to force voltage into the other battery.

I don't think it's a good idea.

You need VERY closely matched batteries or there will be significant energy loss in the imbalances between the two packs. If you're going to be using any cell in parallel you need to make sure they are as close as possible if not directly next to each other in the assembly line during production as they're going to have virtually identical charge/discharge and 'wear' characteristics.

Generally you don't parallel many cells though. In the hobby aircraft industry parallel packs are used a lot with Lithium cells because they don't handle high currents well. Usually it's something like 2 parallel cell packs, but FMA Direct cells intelligent battery monitors/chargers that are for balancing up to 15 packs in parallel, because lipoly packs are so much lighter than any other battery technology they do the parallel bit to make up for their shortcomings.

If you're paralleling batteries make sure they are exactly the same type, and in the same condition - don't parallel a new battery and an old battery, even of the same type.

Paralleling different voltage batteries will destroy BOTH of them.

What sort of batteries are they?

Lead acid batteries are generally safe to parallel providing they're the same voltage, it doesn't even matter if they're different capacities or in different states of charge!