When we saw [Max.K]’s automatic NiMh battery charger float past in the Hackaday tips line, it brought to mind a charger that ...

[Jay Kickliter] built his own coin cell battery ... AA or AAA have NiMH rechargeables in them and have used the same pair for year and years. So we’re happy to see this charger project come ...

Battery chargers are used to recharge batteries which, after discharge, can be restored to a fully-charged state. Rechargeable batteries or secondary cells differ in terms of design and chemistry.