A battery pack for powering a device, comprising: - a battery pack connector for connecting the battery pack to a charger or a device to be powered by the battery pack; - a rechargeable cell having a positive and a negative terminal; - a main bus connecting the positive terminal of the rechargeable cell with a positive connector of the battery pack connector and also connecting the negative terminal of the rechargeable cell with a negative connector of the battery pack connector; and - a battery management system in electrical communication with the rechargeable cell, including: a processor for monitoring an input related to the state of charge of the cell, a switch (340, 350, 360) disposed in a front-side bus between the positive terminal of the cell and the positive connector of the battery pack, the switch responsive to a signal generated by the processor in response to the input related to the state of charge of the cell to control the charging or discharging of the cell; characterised in that the battery pack further comprises a battery pack isolation circuit including a mechanical switch that has a closed condition when the battery connector of the battery pack is connected to a battery charger or device to be powered wherein the battery pack isolation circuit is in electrical communication with the processor, the battery isolation circuit configured to provide a connection signal to the processor indicating that the connector of the battery pack is connected to a battery charger or device to be powered; wherein the processor is configured to respond to the connection signal by sending a signal to the switch to close the switch to provide a voltage across the positive and negative terminals of the connector; wherein the processor is configured to respond to the closed condition of the mechanical switch to provide a voltage across the positive and negative terminals of the connector. - a battery pack connector for connecting the battery pack to a charger or a device to be powered by the battery pack; - a rechargeable cell having a positive and a negative terminal; - a main bus connecting the positive terminal of the rechargeable cell with a positive connector of the battery pack connector and also connecting the negative terminal of the rechargeable cell with a negative connector of the battery pack connector; and - a battery management system in electrical communication with the rechargeable cell, including: a processor for monitoring an input related to the state of charge of the cell, a switch (340, 350, 360) disposed in a front-side bus between the positive terminal of the cell and the positive connector of the battery pack, the switch responsive to a signal generated by the processor in response to the input related to the state of charge of the cell to control the charging or discharging of the cell; characterised in that the battery pack further comprises a battery pack isolation circuit including a mechanical switch that has a closed condition when the battery connector of the battery pack is connected to a battery charger or device to be powered wherein the battery pack isolation circuit is in electrical communication with the processor, the battery isolation circuit configured to provide a connection signal to the processor indicating that the connector of the battery pack is connected to a battery charger or device to be powered; wherein the processor is configured to respond to the connection signal by sending a signal to the switch to close the switch to provide a voltage across the positive and negative terminals of the connector; wherein the processor is configured to respond to the closed condition of the mechanical switch to provide a voltage across the positive and negative terminals of the connector. a processor for monitoring an input related to the state of charge of the cell, a switch (340, 350, 360) disposed in a front-side bus between the positive terminal of the cell and the positive connector of the battery pack, the switch responsive to a signal generated by the processor in response to the input related to the state of charge of the cell to control the charging or discharging of the cell; characterised in that the battery pack further comprises a battery pack isolation circuit including a mechanical switch that has a closed condition when the battery connector of the battery pack is connected to a battery charger or device to be powered wherein the battery pack isolation circuit is in electrical communication with the processor, the battery isolation circuit configured to provide a connection signal to the processor indicating that the connector of the battery pack is connected to a battery charger or device to be powered; wherein the processor is configured to respond to the connection signal by sending a signal to the switch to close the switch to provide a voltage across the positive and negative terminals of the connector; wherein the processor is configured to respond to the closed condition of the mechanical switch to provide a voltage across the positive and negative terminals of the connector.