Low Voltage Battery Monitor Floats into High Voltage Electric Vehicles

January 02, 2021 //By Christopher Gobok, ADI
Low Voltage Battery Monitor Floats into High Voltage Electric Vehicles
If you are not already driving an electric vehicle (EV)—hybrid electric vehicle (HEV), plug-in hybrid vehicle (PHEV), or all-electric vehicle—chances are, you may be soon. Range anxiety has become a thing of the past. Battery monitoring systems are a key element in this context.

EV Movers

You can now help preserve the environment without worrying about being stuck in it. Governments around the world offer generous financial incentives to offset the premium prices of EVs, hoping to steer you away from buying internal combustion engine (ICE) vehicles. Some governments have taken the step of mandating auto manufacturers build and sell EVs, hoping the market will eventually be dominated by them, while others have drawn a more distinct line in the sand; Germany, for example, is already pushing to ban ICE vehicles by 2030.

For much of the automobile’s history, innovation has focused on improving fuel burning efficiency of the ICE, cleaning up emissions while providing a comfortable user experience. However, the vast majority of recent innovations in ICE automobiles are a direct result of advancements in electronics—improvements in chassis systems, power trains, autonomous and advanced driver assistance systems (ADAS), infotainment, and safety systems. EVs feature many of the same electronic systems as ICE vehicles, plus, of course, the drive train itself. According to Micron Technology, the electronics portion of an EV’s value is as much as 75%, with that portion increasing as advances in semiconductor technology continue to drive down the cost of various electronic modules and subsystems. Even nontraditional automotive players, such as Intel, are looking for a piece of the action.

Not surprisingly, of all the electronic subsystems in an EV, manufacturers and consumers alike focus on the heart of the EV, the battery system. The battery system includes the rechargeable battery itself, lithium-ion (Li-Ion) being the current standard, and the battery management system (BMS), which maximizes battery usage and safety. Analog Devices’ BMS solutions are the standard for monitoring them. ADI’s LTC2949 EV battery pack monitor is the newest addition to a wide portfolio of smart BMS ICs that are boosting next-generation EV BMS designs.

BMS Monitoring

A BMS’s primary function is to monitor the state of a battery or, in the case of EVs, a very large pack or stack of batteries. A BMS typically monitors individual cell and pack voltages, currents, temperatures, state of charge (SOC), state of health (SOH), and other related functions, such as coolant flow. In addition to the obvious safety and performance benefits afforded by BMS, accurately monitoring these parameters generally translates to a better driving experience, where drivers are well-informed of real-time battery conditions.

To be effective, the BMS measurement circuits, such as the new LTC2949 pack monitor, must be precise and fast, have high common-mode voltage rejection, consume low power, and securely communicate with other devices. Other EV BMS responsibilities include recovering energy back into the battery stack (that is, regenerative braking), balancing cells, protecting the battery stack from dangerous levels of voltage, current, and temperature, and communicating with other subsystems (for example, chargers, loads, thermal management, and emergency shutdown).

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