With most of the chairs I've encountered, motorized actuators often complicate battery removal/replacement -- the chair is often in an inconvenient position or orientation to facilitate access to the batteries.

A trick that I use (as I refurbish a lot of chairs, many of which have toasted batteries by the time I see them) is:
  • open the circuit breaker/fuse to the main battery pack (this effectively disconnects the dead battery from the circuit)
  • supply power to the charger port (but NOT from the charger)
  • operate the actuators (and ONLY the actuators as the wiring to the battery from the charger port is only intended to carry the charging current, not full motor current!)
  • remove power

I've done this frequently enough on Permobil chairs that I made a little "jig" to simplify the task (I borrow the battery pack out of a UPS to provide the 24VDC). For me, this is much easier than using the "hand crank" to lift the seat (which still leaves the leg rests in an inconvenient position!)

[I have another trick that uses the existing charger to do this but I fear that's getting too far afield...]