Active equalizing and protecting system of stackable series-connected lithium battery

The invention relates to an active equalizing and protecting system of a stackable series-connected lithium battery. A coprocessor is connected with a processor by a serial peripheral interface (SPI) bus; each equalizing unit comprises a single battery and an equalizing circuit, wherein every adjacent two equalizing units are connected in series as follows: a first equalizing circuit and a first single battery are connected in parallel; the first equalizing circuit comprises a first P channel metal-oxide semiconductor field effect transistor (MOSFET) and a first N channel MOSFET; the drain electrodes of the two MOSFETs are connected, the gate electrodes of the two MOSFETs are connected, and the two MOSFETs are connected with the coprocessor through a first signal input end; the source electrodes of the first MOSFET and second MOSFET are respectively connected with the positive pole and negative pole of the first single battery in parallel; the positive pole of the second single battery is connected with the n