Thermal runaway has never been far from the minds of design engineers who use lithium-ion batteries, especially since the first reports of laptop fires surfaced more than a decade ago.
Electronics suppliers are helping engineers prevent such problems with the introduction of new battery management integrated circuits that monitor voltage, temperature, and current conditions at the battery.
"The main condition is overvoltage," says Yevgen Barsukov, IP development manager for battery management systems at Texas Instruments. "Normal voltage for a lithium-ion battery is 4.2V. If the battery is charged to 4.3V or 4.4V, it can take you to a condition where you have thermal runaway."
TI's bq275xx family of battery management ICs provides protection for battery packages. The ICs, which measure just a couple of millimeters on a side, include a microcontroller, flash memory, random access memory, and an analog-to-digital converter. The devices serve as gauges for handheld devices such as cell phones, laptops, and tablets.
Both TI and Analog Devices make management units for electric vehicle batteries. In June, TI unveiled bq76PL536, a battery management unit targeted at rechargeable lithium-ion packs for EVs, hybrid vehicles, and power tools. Last year, Analog Devices rolled out the AD8280, which works with a series of high-voltage comparators to "look" for undesirable voltage or temperature conditions in vehicle battery packs.
"The idea is to monitor for voltage, temperature, and overcurrent conditions," Barsukov says. "If any of the conditions are exceeded, the battery management system will turn off the appropriate components."
For a related deep dive into high-energy rechargables, see our feature-length article, New Breed of Lithium Batteries.