Dell S500 Projector - Manual (Page 48)

NOTE: During the charging process, Interactive Pen amber battery light will be
lit all the time until the charging completed.
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™.
Using Your Projector 48