Canon PowerShot S3 IS Advanced User's Manual page 140

If battery usage time is considerably low despite their
terminals' being wiped and the battery charger's indicator
remaining lit, it is possible that the batteries have reached the
end of their lifespan. Switch to different, unused batteries. If
you are purchasing new batteries, look for Canon AA-size
NiMH NB4-300 (NB-3AH set of 4) batteries.
Leaving batteries in the camera or charger may damage it
causing battery leakage. Remove batteries from the camera
or charger and store in a dry cool location when not in use.
It takes approximately 4 hours 40 minutes with four for the
charger to fully recharge them (as determined by testing at
Canon facilities). Please do not charge batteries in areas
where the temperature is outside the range of 0 to 35 °C
(32 to 95 °F).
Charging time varies according to ambient temperature and
to the batteries' initial charge state.
The battery charger may emit noise while charging. This is
not a malfunction.
You can also use Battery/Charger Kit CBK4-200.
138