ams AG has come up with what it says is “a vastly simplified and more robust” way to monitor and balance cells in lithium ion battery systems, including those in hybrid and electric vehicles.
Bernd Gessner, Senior Vice President and General Manager of Automotive Business at ams, says the currently prevailing method of cell balancing requires a complicated algorithm running remotely on a high-end microcontroller (MCU).
His firm has developed a chip that eliminates the need for the MCU, the software, and the serial communications link that connects the battery system with the MCU.
The chip, AS8506, is said to be ideal for all lithium-based cell chemistries, including those found in hybrid and fully electric vehicles, as well as for electric double-layer capacitors (EDLCs, also known as supercaps or ultracaps).
He describes the ams alternative as a fully autonomous cell management architecture.
According to Gessner, existing cell monitoring ICs are typically limited to the sequential capturing of cell voltage measurements that must be processed by a host controller. That requires streaming large amounts of data over a serial link that is vulnerable to interference in noisy environments.
Plus, sequential cell measurements require complex compensation algorithms to produce valid voltage and current readings across a stack of cells. Software development is time-consuming and costly, and the software requires a good deal of testing to qualify for use in ISO 26262-compliant systems.
The AS8506 captures simultaneous measurements that require no compensation. It can implement passive and active cell balancing autonomously or support an MCU-based system via its serial peripheral interface. An analog circuit in the chip compares up to seven cell voltages against an internal or external reference with 1mV accuracy. Cell voltage measurements can also be digitized with an accuracy of 5mV and reported to a host controller.
“The AS8506 marks a breakthrough in cell monitoring – not an incremental improvement on previous cell monitoring ICs, but a completely new approach,” says Manfred Brandl, ams Product Manager for battery management in the automotive business unit.