At 01:35 PM 1/31/99 -0500, Darwin Reynoso wrote:
>Hi
>Can somebody tell me the formula to know how long
>will a battery last supplying a 20 ma load.
>
>Thanks


'snot that simple.  You'd think a 20mah battery would last one hour, but it
will typically give you about half that.
The Amp/Hour rating of a battery is called "C". You need a battery with a
rating of at least 2C in order to get an hour's runtime.  Depending on the
chemistry, this can get a lot worse. Zinc-Air cells can give you a huge
amp-hour rating for their size, but they only like to supply tiny currents.

First, settle on a battery type, (Nicad, Gell, Alkaline..... ) then get
with the manufacturer for current/runtime curves.