Canon EOS R5 C User Manual page 727

Caution
The camera cannot be powered unless a battery pack is in it.
When batteries are depleted, the adapter charges them. In this case, power is not
supplied to the camera.
To protect the battery pack and keep it in optimal condition, do not charge it
continuously for more than 24 hours.
If the charging lamp fails to light up or a problem occurs during charging (shown by
the access lamp blinking in green), unplug the power cord, reinsert the battery, and
wait a few minutes before plugging it in again. If the problem persists, take the
camera to the nearest Canon Service Center.
The charging time required and the amount charged vary depending on ambient
temperature and remaining capacity.
For safety, charging in low temperatures takes longer.
The remaining battery level may decline when power is supplied to the camera. To
avoid running out of battery power, use a fully charged battery when shooting at
regular intervals.
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