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Ams reveals method for Li cell monitoring, balancing

Posted: 17 Oct 2013 ?? ?Print Version ?Bookmark and Share

Keywords:lithium battery system? cell monitoring? balancing? electric vehicle?

Ams has announced what it describes as a simplified and more robust method of implementing cell monitoring and balancing in lithium battery systems. The innovative architecture has been implemented in a highly integrated chip, the AS8506, to perform distributed cell monitoring and balancing operations for stacked cell modules, including Safe Operating Area (SOA) check and passive or active cell balancing, indicated the company.

According to the firm, the architecture is geared for all lithium-based cell chemistries such as those in hybrid and fully electric vehicles' energy storage systems as well as EDLCs (aka Supercaps/Ultracaps).

By deciding which cells have to be balanced locally instead of relying on a complicated algorithm running on an MCU, the AS8506 allows designers to implement a complete cell management system with no requirement for a powerful host controller, complex software and vulnerable serial communication links.

An advanced analogue circuit in the AS8506 compares up to seven cell voltages against an internal or external reference with an accuracy of 1mV. The device also features internal or external adjustable upper and lower cell voltage limits. Cell voltages can also be digitized with an accuracy of 5mV and reported to the host controller. The AS8506 can implement passive and active cell balancing autonomously or controlled via the SPI Interface. Active cell balancing only requires an additional flyback transformer. The control circuit is already integrated in the AS8506.Temperature measurement is carried out through two external NTC sensors.

The fully autonomous cell management architecture enabled by the AS8506 is in stark contrast to the typical system implementations found today using existing cell monitoring ICs. These are typically limited to the sequential capturing of cell voltage measurements that must be processed by a host controller.

The AS8506 cell monitoring IC is available for sampling and supplied in 1,000-unit quantities. Ams additionally provides a non-automotive version called AS8506C, which is also supplied in 1,000-unit quantities.

A stand-alone Cell Balancer Evaluation Kit for the AS8506 is available online from Ams. An active and a passive Balancer Board is also available in the webshop.

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