Here may be a clue. My owner manual mentions that the battery only recharges at certain "charge points", generally at the top and the bottom of the staircase. So if your chair is sitting part way (which they recommend you do for safety so it is out of the way when not in use), it won't charge.

If you hand crank it to a proper charging point then it may be able to recharge. No guarantee, just an idea.

Chez Bay
December 2014