Use safety circuits in battery packs to check voltage and heat. This makes batteries safer and stops them from overheating. Charge batteries the right way by not overcharging them. Keep the charge under 4.20V per cell to make them last longer and avoid short circuits.
[pdf] If you are hooking batteries up in series, connect the positive terminal of one to the negative of the next, and so on. The following formula applies to series circuits: (V total = V 1 +V 2 etc.). This will provide you with extra voltage for the load, but no extra current (I total = I 1 = I 2 etc.).
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