Battery powered stair lifts have a battery located in between your home's outlet and the stair lift's motor. The outlet charges the battery and the battery powers the stair lift's motor. Unlike electric stair lifts, if you lose power to your home, the stair lift will still work. However, the batteries have to be replaced every 18-24 months - increasing maintenance costs. DC stair lifts include rack & pinion drive, cable drive, and heavy-duty stair lifts. Each stair lift listed is designed for homeowner installation. Installation takes approximately 3 hours.
Early stair lifts mostly had alternating current (AC) drive motors which ran at full mains voltage (around 100 volts in North America). An "energy cable" ran alongside or through the rail to carry the power from the supply point to the carriage.
More recently, residential stair lifts have been powered from rechargeable batteries and use direct current (DC). One of the selling points is that a DC stair lift will continue to function during a power outage, provided the batteries are sufficiently charged. Most stair lifts have a charge point where the unit will park to charge its batteries. Some straight stair lifts have the ability to continuously charge no matter where they are left along the track.
With most DC stair lift models the batteries are accommodated within the carriage and travel with it.
Some models, however, were designed with three phase motors and the batteries (three in total) were housed in a cabinet mounted near the top or bottom of the rail. An inverter system was used to convert the DC energy to three-phase AC.
The power rating of drive motors for domestic straight rail stair lifts may be around 250 watts. The power requirement will be greater for heavy loads, very steep inclines, and wheelchair platform stair lifts.