Downsizing 12 volts battery for EV using effective energy management strategies when vehicle is inactive

On electric vehicle the low voltage (nominal 12 volt) battery serves mostly as an energy storage buffer for supporting features and actuators on the 12 volts power supply network. The power management strategies significantly influences the thermal management of the vehicle especially in power critical states. Within an EV, unlike an internal combustion engine car, as there is no cranking requirement needed to be supported by this battery, it presents a significant opportunity for downsizing. This can save from 10 kg-15 kg which could add up to 1 mile of range in combined cycle. In a premium car there are a significant number of features which inhibits the car to go into “deep sleep” and hence remains on a “stand-by” mode of operation. During this period of stand-by the low voltage energy storage system need to be sized for up to 0.4 W of continuous power drain. To sustain longer periods of stand-by mode the low voltage battery needs to have enough stored energy to maintain the appropriate level of state of charge (SOC) so that enough critical threshold of SOC is maintained for 12 volts essential system startup at vehicle restart. This can potentially inhibit downsizing of the low voltage battery. In this paper strategies that enable such downsizing is discussed and results associated with one such strategy is shown in a series production electric vehicle. Off board compute strategies allowing personalisation of such strategies are also discussed in this paper.