on 7/6/06 9:57 PM, Ken Presley wrote: > one of the batteries has a bad cell. OK, thanks for the definitive answer. By the way, I unplugged everything from the UPS except a 25watt light bulb and then unplugged the UPS from the wall. The light stayed on. Also, I plugged in a USB cable to my Mac and powered it up. The Energy Saver Control Panel says that the battery is 100% charged. Is the bad cell still definitive? Thanks.