I have a battery charger capable of balance charging up to 10 cells in series (10S), but most of the batteries I use are somewhere between 1 and 4 cells. I have plenty of experience charging the batteries in parallel, but I'd rather charge them in series. Doing so allows my charger to report out to me details on the health of each individual battery, rather than some aggregate across them all.
Connecting the batteries in series is pretty trivial: connect + on one battery to - on another, make a balance lead tap between each battery and at the ends. The net result looks something like
Balance: | | | |...| Batteries: -C1+-C2+-C3+...+ Charge: - +
The problem is that charging / discharging batteries doesn't actually happen over the balance lead but instead over the charge wires. As a result, I either hard wire the plugs to always charge the same number of batteries or I have to manually adjust which battery the + charge lead goes to.
I've tested this out with a 5x 2S battery rig, but I'd rather have a solution that didn't require I adjust the + terminal each time.
Is there some way I could rig up a simple circuit to detect the presence of a cell and use that to switch where the + lead is hooked up to? For example, in the below diagram, could I use some form of a transistor in a SPDT setup for each of the |---| lines below?
-C1+-C2+-C3+-C4+ | | | | | | | |---| | |-----| | |------| - +