Dell S320 User Manual page 48

NOTE:
During the charging process, Interactive Pen amber battery light will be
lit all the time until the charging process is complete.
NOTE:
For first time use, it takes at least 4-5 hours to fully charge the battery. A
fully charged battery will allow up to 25 hours of non-stop use or up to 4 weeks
in standby.
CAUTION:
If your docking charger cannot charge, contact DELL.
48 Using Your Projector