Canon PowerShot S5 IS User Manual page 167

If you store batteries for a long period of time (about 1
year), it is recommended that you deplete the batteries in
the camera and to then store them at room temperature (0
to 30 °C/32 to 90 °F) in low humidity. Storing them in a fully
charged condition can shorten their lifespan or degrade
their performance.
Again, if you do not use batteries for more than 1 year, fully
charge them once a year and deplete them in the camera
before storing them.
If the battery usage time has become considerably low
despite wiping the terminals and charging them until the
battery charger indicator remains lit, this may indicate that
the batteries have reached the end of their lifespan.
Replace them with new batteries. If you are purchasing
new batteries, look for Canon AA-size NiMH batteries.
Leaving batteries in the camera or charger may result in
damage from battery leakage. When not in use, remove
the batteries from the camera or charger and store them in
a cool, dry location.
It takes approximately 4 hours 40 minutes for the charger to
fully recharge the batteries after they have been depleted
(as determined by testing at Canon facilities).
Charge batteries in an environment where the temperature
is in the range of 0 to 35 °C (32 to 95 °F).
The charging time varies according to the ambient
temperature and to the battery charge state.
The battery charger may emit noise while charging. This is
not a malfunction.
Battery and Charger Kit CBK4-200 can also be used.
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