Multiple Batteries in Parallel
I have several regular 12v batteries that are different sizes. Can I safely hook them up in parallel without damaging any of them?
Forum Discussion
Boon Docker wrote:
BFL13
There was 182 ah left in the 250 and 65 ah left in the 100 after your test.
So in theory if you continued draining them there would be 117 ah left in the 250 and 0 ah left in the 100. Yes?
No, because the current is not shared equally when discharging or charging. The voltage of the two batteries is equal (it has to be, they're connected in parallel, excepting for any tiny difference caused by bad balancing of the wiring), and the current varies however it will to maintain that.
If there are 0 Ah left in the smaller battery, it's voltage would be...umm, say maybe 10V, depending how you define capacity. The other would be at maybe 12.0V or something like that if it had around half its capacity left.
It also works the other way around, with loads rather than batteries. If you plug a lamp with a 100W bulb and a lamp with a 25W bulb into the same outlet, the 25W bulb does not consume as much current as the 100W bulb and burn out more quickly for that reason.
