Hi Zach,

>I recently bought four new C size ni-cad batteries (1.2V 2200Ah).  I
>wired
>them up in series (making 4.8V). I read on the side of the battery
>"Charge
>for 15 hours at 220mA."  Now here is my question- what is an easy way
>to
>keep the current at 220mA.  Sure, you could put a 21ohm resistor in
>series

I like to use a light bulb. When the bulb dosn't glow the battery is
charged.
A five volt bulb might work nicely.

>with the pack, that is if the battery pack had no internal resistance.
> But
>the amount of current drawn by the pack changes depending on how
>charged it
>is.  Am I worrying to much about details?


Yes, You are only in danger of ruining the battery with too much current.


>Well, here is why I ask.  I charged this pack up over 15 hours, and
>then
>connected my pic.  The pic ran for about 5 minutes and then stopped.
>Voltage on the batteries was 4.1V and falling.   I measured the
>current
>drawn by the pic circuit.  It was only pulling about 60mA.  Why didn't
>the
>batteries last MUCH longer?!?
>

Good question, sounds like ether the pack was not suffintly charged or
you do have a
problem.

Carl