like jeremy said check the sensor on the sissor assy and make sure it is registering when the platform is lowered.
Also it would help if you had a JLG handset to connect to it, that would help diagnose it quite easier.
Couple things come to mind about the battery indicator, there is a sensor wire on the charger... make sure it is connected and no open circuits in it. One other thing would be if the reset range on the BDI is off, that might keep it in cutout mode limiting the unit's movement speed. Raising the reset level so that it will reset at a lower voltage might make the BDI reset.
Like i said, having the handset would make things a heck of alot easier ;o)

good luck