Pure electric passenger car battery charge and discharge protection circuit design methods

Source: 2020 - 04 - 11 and clicks: time pure electric passenger car battery charge and discharge protection circuit design method at present, the pure electric passenger car battery installation is usually in the battery box installed several parallel battery module, and then in the passenger car battery fixed a number of cells in the body. Because of the pure electric bus using power battery has quite part of it is direct charging, namely all the battery module on the vehicle are charging together. At the same time, the same car battery module of different capacity and internal resistance is different also. Therefore, the increase of the charge and discharge time, voltage imbalance, and other aspects of different battery SOC module will become more and more obvious [ 9] , lead to the fact that some of the battery module will be fully charge and discharge, and some people can lead to overcharge or overdischarge. A pure electric city bus has nine battery box. Each battery box by 20 battery modules in series. Each battery module consists of 32 12. 5ah / 3. 2 v lithium iron phosphate batteries in parallel. As a result, each module of the battery capacity is 400 ah, nominal voltage of 3. 2v; The vehicle battery total capacity of 400 ah, nominal voltage of 576 V. Ac asynchronous motor rated power of 100 kW, the rated voltage of 576 V, the minimum working voltage is 450 V, the maximum working voltage is 700 V. In order to prevent the battery overcharge or overdischarge, EV200 relays in series in each box between the 10th and 11th of the battery module. Rated current is 200 a, control current of 100 ma. 20 battery module is divided into two parts, 10 series, every part of battery module directly, each battery box of a EV200 relay connection between the positive and negative. Normal charge and discharge, battery module in series between the relay is closed, the battery box sre disconnect between the positive and negative, in order to keep the battery module can be normal charging and discharging inside the box. When charging, when the battery module with the highest voltage charge inside the box, a battery pack sre disconnect between the battery module, battery box series relay closed between the positive and negative terminals. Battery pack inside the box to stop charging, ensure that other normal rechargeable battery box module; The last box of battery fully charged, the charger automatically shut down. When unloading, when a box to minimize the battery voltage module, relay module series disconnect between box, while the relay box between the positive and negative terminal series closed, battery pack will stop discharging the cargo. At this point, the motor will be power brownouts and a corresponding alarm, charging near to remind the driver to maintain the battery. Therefore, can avoid relay between two or more battery pack disconnect at the same time, lead to low voltage drop, the situation of the motor can't work normally.