Spece,
The battery voltage to operate the lift should be reading 13.5 to 14.5. If you are showing 12.6 volts at the battery, it is almost dead. Any electric lift that states it operates on a certain voltage; the battery is dead when it drops to that voltage. The lift may still function but operating it on lower voltage will heat up the system and cause damage over time. Should you charge the battery, and the lift stills moves slow, you may need to have the throttle calibrated. Good Luck.