a large bunch of those guys simply tell you to raid battery recycling bins and test batteries - a lot of people toss good batteries out.
another group are selling a magical battery charger with special fairy dust that will allow you to power a house with an old AA battery.
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don't try to recharge the alkaline type batteries unless they are designed for it - the outgassing can damage the casing. then the battery will leak inside the equipment.
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NiCads can be conditioned. dendritic growth can be corrected for awhile, lengthening the number of recharges possible.
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I don't know alot about lithium LiPo/LiFo chemistry.
Zinc air won't recharge as the zinc oxidizes in the discharge cycle.
