Charging and discharging an electric vehicle (EV) battery requires caution; EV batteries contain the energy equivalent of a small explosive, after all. Over-voltage or under-voltage conditions can lead to thermal runaways that could cause battery failure serious enough to injure passengers.
The challenge is balancing the need for optimal battery performance and life with safety. Clearly, the battery management system (BMS) has to incorporate a high degree of intelligence, in addition to monitoring components and power conversion stages.
Typically, the monitored operating parameters are precisely and quickly routed to higher-order, intelligent battery management controllers (BMCs) that can detect potential hazards and take pre-emptive corrective action, such as shutting down a battery cell that is overheating. Also calculated from monitored data: The state-of charge (SOC) of the battery, which is used to determine the remaining charge and, thus, the available range of travel; and state-of-health (SOH), which provides important insight into the operating conditions of the battery so that its remaining lifespan can be projected and the appropriate maintenance procedures recommended.
All this intelligence requires serious computing horsepower. Microcontrollers have to adjust to changing properties of batteries, respond quickly to overvoltage conditions and - in on-board charging - run computationally intensive algorithms.
The white paper Intelligent battery management and charging for electric vehicles explores the challenges to designing power systems that can be adapted to a wide variety of batteries, in different types of vehicles