Sony DSC-W310 - Manual (Page 26)

GB
26
On the internal rechargeable backup battery
This camera has an internal rechargeable battery for maintaining the date and time
and other settings regardless of whether the power is on or off.
This rechargeable battery is continually charged as long as you are using the camera.
However, if you use the camera for only short periods, it discharges gradually, and if
you do not use the camera at all for about one month it becomes completely
discharged. In this case, be sure to charge this rechargeable battery before using the
camera.
However, even if this rechargeable battery is not charged, you can still use the
camera, but the date and time will not be indicated.
Charging method of the internal rechargeable backup battery
Insert a charged battery pack in the camera, and then leave the camera for 24 hours
or more with the power off.