This is not exactly a pic question, but it is about the battery pack I am
using to power a pic.

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
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?

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?!?

I am either not charging the pack correctly or I have a bad cell.  If I
have a bad cell, is there any easy way to test this? They were supposed to
be new batteries, they were expensive ($7 bucks each) .

Thanks for any advise,

Zach