Using Car Energy More Efficiently

System ensures that cells hit the sweet spot

There was a time when automobiles were a lot simpler: four tires, an engine, manual transmission and a seat—that’s all you needed to get from point A to point B. OK, that may be oversimplifying it a bit, but cars were a lot more mechanical back in the day. Now, however, it seems as if almost every component is controlled by its own computer, and each microchip communicates to another in an effort to provide the best driving experience.
So it only makes sense that Johnson Controls would develop a battery management system (BMS) for its line of hybrid batteries, offering automakers—and ultimately consumers—an outstanding battery that interacts with other automobile systems, adjusting performance to match ever-changing conditions, via printed circuit boards and microprocessors.
“The battery management system is a hardware device with embedded software that monitors, controls and communicates with individual cells that constitute the entire battery system,” says Mike Andrew, director of Government Affairs and External Communications for the Hybrid Systems Unit at Johnson Controls. “It also communicates with other vehicle microprocessors, such as the powertrain control unit, to ensure that overall functionality is seamless, safe and efficient.”

Hitting the Spot

While the BMS can differ from vehicle platform to platform depending on manufacturer specifications, the overall system is designed to save energy. In fact, the BMS ensures the hardware and the battery cells themselves are being continually used in their “sweet spot,” the range in which optimal charging and functionality comes into play.
“A [specific] chemistry would operate ideally within a certain state-of-charge range, a certain voltage range and a certain temperature range,” Andrew says. “The BMS, by monitoring the cell condition, the energy going in and out of those cells and their temperature response, can act to help control the conditions that are imposed upon those cells to make sure they stay within their sweet spot.” That then helps in maintaining reliable battery performance, acceptable battery life and overall automobile functionality.

In Sync

Because a battery can consist of 100 or more cells, it’s vital to ensure that all cells are performing identically by way of the BMS. Otherwise, a weaker performing cell could start to degrade the whole battery system, aging it prematurely. “The battery management system is critical to ensure uniform use and performance for all those cells—so they essentially operate as a team,” Andrew says. And that teamwork can help to make hybrids, plug-in hybrids and electric cars more performance-driven overall.