BPMS THERMAL MANAGEMENT SYSTEM
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interface allows for data exchange with the EV controller, and the traction drive train controller via the HSDB interfaces over the EV communication bus. Thus operational limits for the battery current draw, control for regenerative braking as a function of the SOC of the battery are communicated to and from the vehicle bus. The HSDB also provides warnings, alarms, and diagnostic messages to the driver’s console. Auxiliary inputs are interfaced to the MC for direct hardware functions, including the ignition key or park-drive selector interlocks, charging station connector interlock, gas ventilation, and cooling fans. In addition, there is an input for the ambient air temperature sensor. A primary function of the BPMS is to provide system safety. Since BPMS has total control over vehicle charging, all safety features, including driver ignition lock-out, charge-line continuity, charger-polarity check, and line-current leakage are controlled by BPMS prior to applying power to the EV under BPMS control.
BPMS THERMAL MANAGEMENT SYSTEM The operating conditions of the vehicle batteries consist of variable environmental conditions and variable electric power demands. Chemical processes in the battery are temperature dependent. Therefore, the electrochemical storage system will have to be kept within certain temperature limits in order to maintain a proper function and also to ensure a reasonable battery life. The temperature limits for the battery are considered to be 10°C as the lower limit due to decreasing battery capacity and 50°C as the upper limit due to positive plate corrosion and separator decomposition. From the battery thermal management standpoint, it is necessary to maintain a uniform temperature within the battery pack. The thermal management system will provide either heating or cooling action depending upon the battery pack conditions. Tests conducted in the laboratory and with EV urban driving suggest that using a thermal management system improves the mileage and battery life by at least 20%. Thermal management of the battery pack is essential both for normal urban driving and rapid overnight charging where charger current levels of hundreds of amperes are applied to the battery pack for relatively short duration. Although maintenance-free starved electrolyte or gelled-electrolyte VRLA batteries are being used commonly, these batteries overheat more rapidly than the flooded lead-acid counterparts. This is owing to the fact that the VRLA batteries are unable to dissipate heat generated by gas
