If a customer wants to have a battery percentage on the screen of a windows mobile device it can be added with a 3rd Party program called Ariel 2.1
http://forum.xda-developers.com/showthread.php?t=364278
It can be added to the Applications > sSartup folder on the windows mobile device
Reboot the unit and when the device come back up the battery percentage will replace the Start Menu logo in the upper left hand corner.