basic Questions on Power engineering

Hello!

--> I was wondering how a battery charger really works? Does it provide the same amount of voltage and current to the battery that battery provides?

--> how do I calculate the time it needs for the battery to be charged?

thanks! vandra

Reply to
vandra
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No, it must provide more voltage than the battery provides. The current must flow into the battery to charge it. If the voltage were the same no current would flow.

The specifics depend on the battery technology and the battery design, but generally the time needed would be equal to the charging current divided by the capacity of the battery with some inefficiency thrown in (which is a function of the charging current and the battery). A double-A NiCd, for instance, might have a capacity of 2000mAh. If you charged it with

100mA for twenty-four hours (2400mAh) it would be pretty close to being fully charged (2400/2000 = 20% wasted as heat).
Reply to
Keith

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