Heavy Duty Stair Lifts are not that much different than your standard stair lift. Most of these units have a additional bracket or larger post on the seat to help with a higher weight capacity. These units have either a 400 lb or a 600 lb weight capacity. The Harmar SL600HD has the largest weight capacity at 600 lbs. The Bruno Elite stair lift has a 400 lb weight capacity and has an option for a larger seat.
These units are battery operated with charge plates that allow the stair lifts to be charged while not in use. This helps in case of a power failure. You typically will be able to use one of these stair chairs 10 to 15 times before power one need to be turned back on.