Cell monitoring IC for battery cell management systems

24th October 2013
Nat Bowers

ams have today annoucned a vastly simplified and more robust method of implementing cell monitoring and balancing in lithium battery systems.  A new highly integrated chip, the AS8506 performs distributed cell monitoring and balancing operations for stacked cell modules, including Safe Operating Area checks and passive or active cell balancing.

Ideal for all lithium-based cell chemistries, such as those found in hybrid and fully electric vehicles, as well as for EDLCs (also known as supercaps or ultracaps), the AS8506 implements both passive and active cell balancing autonomously as well as supporting a microcontroller-based system via its Serial Peripheral Interface.

Rather than a complicated algorithm running remotely on a high-end microcontroller deciding which cells have to be balanced, the new architecture of the AS8506 controls balancing locally at the cells. This enables designers to implement a more streamlined cell management system that eliminates the powerful host controller, complex software and vulnerable serial communication links normally used today.

Comparing up to seven cell voltages against an internal or external reference with an accuracy of 1mV, the AS8506 features an advanced analog circuit which supports cell-balancing and cell-monitoring functions. Cell voltage measurements can also be digitized with an accuracy of 5mV and reported to a host controller.

Integrating a control circuit, the AS8506 features internally or external adjustable upper and lower cell voltage limits. Active and passive cell balancing use a similar circuit design, but active balancing requires an additional flyback transformer. Temperature measurement is carried out through two external NTC sensors.

Manfred Brandl, Product Manager for battery management in the automotive business unit at ams, comments: “A breakthrough in cell 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.”

Available for sampling now, the AS8506 cell monitoring IC is priced at $9.10 for 1,000 pieces. ams also provides a non-automotive version called the AS8506C, priced at $7.80 for 1,000 pieces. A stand-alone Cell Balancer Evaluation Kit for the AS8506 is priced at $80. An Active/Passive Balancer Board is also available at the ams online webshop, priced at $100.

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