Abstract: A system for retaining a battery on a frame of a vehicle has a retaining device which is movable between a first position at which the battery is free to move in a passing relationship relative to a side of the frame and second position at which the battery is retained on the frame and from passing movement relative to the frame side. A sensing device delivers electromagnetic radiation, receives electromagnetic radiation and delivers a first control signal in response to receiving electromagnetic and delivers a second control signal in the absence of receiving electromagnetic radiation. An obstructing device is movable to block the sensing device from receiving electromagnetic radiation in response to the retaining device being at the first position. A controller receives the first and second signals and delivers a vehicle disabling signal in response receiving the second signal. The system is particularly suitable for use on an automatic guided vehicle.