hi.......common problems with all battery run stairlifts are the main carriage batteries which only last approx 3 to 5 years in some cases less.......one of the tests to confirm it is the batteries is as you have done already and that is hand wind lift up so far and call it back down..this will be testing lift not underload....first i would checked to see if spur supply is switched on as this can be switched off by mistake and drain carriage batteries......let us know if this helps.......regards
IAN.......PORTSMOUTH, April 2011