A lift assist device preferably includes a pair of lift units and a battery. Each lift unit preferably includes a linear actuator, a lift projection, a top bracket and a bottom bracket. A screw sled extends from one side of the linear actuator. An end of a lift projection is secured to the screw sled. One end of the top bracket is attached to a top of the linear actuator. One end of a bottom bracket is attached to a bottom of the linear actuator. The top and bottom brackets will be different depending on whether they are attached to rollators, wheelchairs, motorized wheelchairs and motorized scooters. The lift assist device may be used to help lift a user from a chair adjacent the rollator, wheelchair, motorized wheelchair or motorized scooter, or when the user is seated in rollator, wheelchair, motorized wheelchair or motorized scooter.