Why do battery chargers (the type that charges AA and AAA battery’s) require 2 battery’s before actually charging them?
In: Technology
Because they charge both batteries in series, at the same time. While you put the batteries in end-to-end, the negative end of one battery is connected to the positive of the other, and the charger provides ~2.4 volts across the pair of cells, charging them to 1.2 each.
This is sort-of OK with NiMh or NiCd cells, because you can gently overcharge them without causing damage. But these chargers have to charge them slowly, and it isn’t really good for them. If you are charging Lithium cells, though, you have to monitor each cell individually, and have some balancing step to charge all of them and not overcharge any.
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