NTLK Overcurrent

From: Gruendel, Frank 3837 PPE-WT (Frank.Gruendel@de.heidelberg.com)
Date: Tue Sep 05 2000 - 04:43:06 CDT


>mY KNOWLEGE OF ELECTRONICS IS LIMITED BUT (sorry, caps lock) don't
elecrical
>items basically ask for a certain amount of watts and as long as the power
>supply can provide it then you're okay?

Sometimes. Roughly speaking, the current an electronic device draws depends
on
its interior resistance. Unfortunately, rechargeable batteries have an
interior
resistance that is extremely low, very close to zero if they are intact.
This is why you can get hundreds of amperes out of a car battery which will
effectively melt a thick wire you use to short it. Even a fully charged tiny
AA battery can deliver > 10 amperes or more if shorted.
This also works in the other direction, and this is the reason that the
charge
current needs to be limited. If you don't, the cells will draw so much
current
that they (and probably you) will be damaged for life very fast.

Frank
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