Our machines have the "power outage" memory, so there must be a battery inside. My manual does not say anything about how to change it. Are you using the front screen on/off button or the power on/off switch in rear? If you use the rear switch that kills all power and may lose the charge. The front screen button turns off the LED's, but leaves the board powered up. JT sent me some extra manuals because around here things disappear regularly- he could probably send you another.