Polaroid PMP350-4 - Manual (Page 10)

Charging the battery
Your MP3 Player has an integrated rechargeable Li-ion battery. It is recommended to fully charge the player before using it for the first time.
Recharge the battery by connecting the player to a computer using the included USB 2.0 cable.
Charging time is between 3-5 hours, depending if the player is powered off or working. To keep the battery in good condition, we recommend not
charging it for more than 8 hours.
A fully charged battery will give approximately 6 hours of playback time.*
* Depending on playback mode.
Important:
● Fully charge it before you use the player for the first time or when you haven’t used it for a long time.
● Charge the player immediately when the “Low battery” message is displayed.
● Do not over charge or discharge the player. Over charging or discharging will shorten the battery life.
● The battery could be over discharged if the player is not used for a long time (over three months). To avoid over discharge, fully charge the player
every three months and always keep the voltage of the battery above 50 %.