BATTERY SYSTEM WITH PARALLEL JOINING PROTECTION

A battery pack includes a housing having a positive terminal and a negative terminal. Battery cells are located within the housing and are selectively coupled to the positive terminal and coupled to the negative terminal. A battery management system is located within the housing and is configured to operate a first switch within the housing to selectively couple the battery cells and the positive terminal. A bleed circuit is electrically coupled between the positive terminal and the negative terminal. The bleed circuit includes a resistor and a second switch to selectively couple the positive terminal to the negative terminal. The battery management system is configured to open the first switch and close the second switch and measure a voltage drop across the resistor to detect a presence and type of voltage source connected to the positive terminal.