ams AG, an Austrian provider of analog ICs and sensors, has introduced a simpler and more robust method of monitoring and balancing cells in lithium-ion battery systems.
The company has implemented the new architecture in a highly integrated chip, the AS8506, to perform distributed cell monitoring and balancing operations for stacked cell modules, including Safe Operating Area (SOA) checks and passive or active cell balancing. It’s designed to work with all lithium-based cell chemistries, as well as EDLCs (aka supercaps or ultracaps).
In conventional systems, a complicated algorithm running remotely on a microcontroller decides which cells have to be balanced. The new architecture supported by the AS8506 can control balancing locally at the cells, enabling designers to implement a more streamlined cell management system that eliminates the host controller, complex software and vulnerable serial communication links.
The AS8506 can implement both passive and active cell balancing autonomously, or it can support a microcontroller-based system via its Serial Peripheral Interface. An analog circuit in the AS8506 compares up to seven cell voltages against an internal or external reference with an accuracy of 1 mV, to support cell balancing and cell monitoring functions. Cell voltage measurements can also be digitized with an accuracy of 5 mV and reported to a host controller.
Active and passive cell balancing use a similar circuit design, but active balancing requires an additional flyback transformer. The control circuit is integrated in the AS8506. The device also features internally or external adjustable upper and lower cell voltage limits. Temperature measurement is carried out through two external NTC sensors.
“The AS8506 marks a breakthrough in cell monitoring – not an incremental improvement on previous cell monitoring ICs, but a completely new approach”, said Product Manager Manfred Brandl. “By offering local cell and temperature monitoring, the AS8506 gives system designers a simple and robust means to implement a battery management system, with just a simple microcontroller required for basic system functions.”
ams is demonstrating the AS8506 at the VDI Congress on ‘Elektronik im Kraftfahrzeug’ (Baden-Baden, Germany, 16-17 October 2013).