A lift system comprising a rail; a carriage assembly comprising a seat or platform for supporting a person to be conveyed along the rail, drive means arranged to engage the rail and controllable to drive the carriage assembly along the rail, energy storage means arranged to power the drive means, input means operable by a user to provide an input signal indicative of a desired movement of the carriage assembly along the rail, and control means arranged to receive said input signal and control said drive means in response to said input signal; and charging means arranged to charge said energy storage means when the carriage assembly is at a first charging position on the rail, wherein the control means is arranged to monitor at least one voltage characteristic of the energy storage means, and generate an alert signal in response to one or more of said characteristics, or a difference between one or more said characteristics, fulfilling a defined criterion, criteria, condition, or conditions, and wherein the energy storage means comprises a first battery or first battery pack, having respective first and second battery terminals, and a second battery or second battery pack, having respective first and second battery terminals, the first and second batteries or battery packs being connected in series with one another to supply a drive current to the drive means, wherein said at least one voltage characteristic comprises a first voltage between the first and second battery terminals of the first battery or first battery pack and a second voltage between the first and second battery terminals of the second battery or second battery pack, wherein said fulfilling of a defined criterion, criteria, condition, or conditions comprises: one of the first and second voltages falling below a threshold value; or a difference between the first and second voltages exceeding a threshold value. a rail; a carriage assembly comprising a seat or platform for supporting a person to be conveyed along the rail, drive means arranged to engage the rail and controllable to drive the carriage assembly along the rail, energy storage means arranged to power the drive means, input means operable by a user to provide an input signal indicative of a desired movement of the carriage assembly along the rail, and control means arranged to receive said input signal and control said drive means in response to said input signal; and charging means arranged to charge said energy storage means when the carriage assembly is at a first charging position on the rail, wherein the control means is arranged to monitor at least one voltage characteristic of the energy storage means, and generate an alert signal in response to one or more of said characteristics, or a difference between one or more said characteristics, fulfilling a defined criterion, criteria, condition, or conditions, and wherein the energy storage means comprises a first battery or first battery pack, having respective first and second battery terminals, and a second battery or second battery pack, having respective first and second battery terminals, the first and second batteries or battery packs being connected in series with one another to supply a drive current to the drive means, wherein said at least one voltage characteristic comprises a first voltage between the first and second battery terminals of the first battery or first battery pack and a second voltage between the first and second battery terminals of the second battery or second battery pack, wherein said fulfilling of a defined criterion, criteria, condition, or conditions comprises: one of the first and second voltages falling below a threshold value; or a difference between the first and second voltages exceeding a threshold value. one of the first and second voltages falling below a threshold value; or a difference between the first and second voltages exceeding a threshold value.