I'm building a small led project that has a donut shape, and I will need more amp hours than can be fit using one lithium battery, given the constraints of the housing. I think it will work fine with two batteries in there, but not sure how to implement the charging circuit for them. I understand that lithium batteries need to have a balance charge circuit - could I just use two charge modules that each takes care of its individual battery and parallel the outputs? If not, does anyone have a link to a balancing circuit to learn from? Thanks!
Ampere-hours add if you connect the batteries in parallel. No balancing charger is needed.
Voltages add if you connect them in series, then you need the balancing charger.
Make sure that the batteries have the same state of charge before wiring them in parallel.
Thanks @jremington. Yes, the thought was to put the batteries in parallel to increase the amp hours. You said no balancing charger was needed in that arrangement, but I would have thought that if, as they degrade, one battery ends up with a different charging capacity than another, it might cause a problem similar to the one you might get if you were to parallel them while they are at a different charge state - one battery might be trying to charge the other. Not so?
Batteries used in any combination of series, parallel or both have that problem. You can buy or make battery capacity meters, and match them yourself.
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