Minivator 1000 Stair Lift Dead?

Trying to help my neighbour out here.

The 1000 was installed around 4 years ago for his wife. She sadly passed away at the beginning of December & the lift has remained used (& unfortunately powered off) until now. It's now dead.

I have accessed the batteries & both are flat but there is also little to no charging voltage present. 1.2V on one side & nothing on the other. Should there be a charging voltage present or does the charger detect that the batteries are unable to take a charge & so shut down?

There is around 33V present on the charging points but it looks like the chair may have slightly overshot. Now I know where the manual winder goes I'll try winding it back.

Is battery replacement a feasible DIY job? I think I read on another thread that the chair needs to come off the track which requires a special tool.

Grateful for any assistance.