Sounds like one of the batteries went south on you; usually a dead cell or a shorted cell. You'll have to unplug the joystick, remove the seat and the shroud to get to the batteries after the chair has dropped down to the yellow, or to red. Measure the voltage on each battery. If it is just one, it will read something like 11 volts or much less, compared to a good one that should read around 13. Your batteries should have at least a 6 month warranty for replacement.