Abstract: A balanced charging/discharging circuit for a lithium battery set, including a plurality of serially connected lithium batteries each having a positive electrode controlled by a corresponding control signal to selectively establish connection with a positive electrode of a battery charging circuit, and a negative electrode controlled by a corresponding control signal to selectively establish connection with a negative electrode of the battery charging circuit. Voltage of the positive and negative electrodes of each of the serially connected lithium batteries is transmitted to a corresponding terminal of a control circuit respectively so that the control circuit generates a corresponding transfer signal to the battery charging circuit and supplies the control signal to establish connection of a corresponding series of lithium batteries for charging. Battery sets arranged in series or in parallel can be charged with the maximum current and the service life is extended and charging time is shortened.

Abstract: A protection circuit for a lithium battery pack that serves as a power source of a power tool is arranged in the lithium battery pack and connected among a reversal/forward rotation circuit, a speed variation circuit, and a motor of the power tool. During a discharging process, the protection circuit detects battery voltage and temperature and when abnormal events occur, the protection circuit cuts off the discharge current. The protection circuit has a simple structure, low costs, and is easy to incorporate to the currently existing pressing-control circuit of the power tool.

Abstract: A protection circuit for a lithium battery pack that serves as a power source of a power tool is arranged in the lithium battery pack and connected among a reversal/forward rotation circuit, a speed variation circuit, and a motor of the power tool. During a discharging process, the protection circuit detects battery voltage and temperature and when abnormal events occur, the protection circuit cuts off the discharge current. The protection circuit has a simple structure, low costs, and is easy to incorporate to the currently existing pressing-control circuit of the power tool.