Canon EOS 1D Mark III Instruction Manual page 27

Tips for Using the Battery and Charger
Recharge the battery on the day before or on the day it is to be
used.
An unused charged battery will still gradually lose its power over
time.
After recharging the battery, detach it and unplug the power
cord from the power outlet.
When not using the battery and charger, attach the protective covers.
Use the battery in an ambient temperature range of 0°C - 40°C /
32°F - 104°F.
To attain best battery performance, an ambient temperature of
10°C - 30°C / 50°F - 86°F is recommended. In cold locations such
as snowy areas, battery performance and operation time may
temporarily decrease.
When not using the camera, remove the battery.
If the battery is left in the camera for a prolonged period, a small
amount of power current is released, resulting in excess discharge
and shorter battery life. Take out the battery from the camera and
attach the protective cover before storing. Storing the battery after it
is fully charged can lower the battery's performance.
The battery charger can also be used in foreign countries.
The battery charger is compatible with a 100 V AC to 240 V AC 50/
60 Hz power source. Use a commercially-available plug adapter for
that country. Do not attach any portable voltage transformer to the
battery charger. Doing so can damage the battery charger.
Check the battery performance.
While the battery is recharging, press the
<PERFORMANCE> button to check the
battery's performance level indicated by the
Charge level indicator.
(Green): Battery performance is fine.
(Green): Battery performance is slightly degraded.
(Red): Replacing the battery is recommended.
Recharging the Battery
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