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Battery management system

Supervising lithium-ion batteries

Sensor-Technik Wiedemann (STW) will show its battery management system mBMS for lithium-ion batteries at the Hanover fair 2016 in April. Communication is undertaken via CAN interfaces.

Communication with the superordinate infrastructure is undertaken via CAN interfaces (Photo: STW)

As a construction kit made of hardware and software components, the mBMS is both an “off-the-shelf” solution as well as a development basis for specific industrial- and vehicle-compatible battery management systems. The focus objectives for application are electrical and hybrid vehicles for road and floor conveyors or industrial mass storage devices for grid stabilization.

STW provides customer-specific adaptation developments based on the mBMS construction kit. The assembly geometries are then adapted and special functions and alternative interfaces are implemented. Thanks to the computer architecture with two controllers (Infineon XC, Infineon Tricore), an application processor is provided which executes customer software without compromising the security functions. In this way, customers can for example incorporate their own algorithms for condition evaluations.

With the mBMS toolchain included in delivery, the battery integrator can configure its battery memory and conduct diagnostics on the running system. Optionally, a special program code can be added, which keeps the timeframe for successful commissioning short. The system is available as an “off-the-shelf” solution in the form of three key assemblies: The central BMS (battery main supervisor), a variety of cell monitoring assemblies (cell sensor circuit), and the current sensor (power measurement board). All assemblies are suitable for battery voltages up to 800 V, and two sensor types are available for 300 A and 600 A for current measurement.

Sensor and actuator functions are also implemented: Monitoring of all cell voltages with the precision measurement module LTC6804 by Linear-Technology, shunt-based current measurement, all-pole disconnection of the battery with installed contactor diagnosis, assessment of crash and interlock signals, adaptive pre-charging of the intermediate circuit, performance prediction in charging and discharging direction, state of charge (SOC) determination with Coulomb counting, and automatic capacity determination.

Many classes of lithium-ion cells are supported. The communication with the superordinate infrastructure is undertaken via CAN interfaces. In this way, it is also possible to conduct remote maintenance and diagnosis with STW ESX controllers and Connex data management solutions. In particular for mass storage devices, it is of advantage to be able to switch batteries in parallel. The mBMS supports this option: up to eight high-voltage storage devices of the same type can be switched in parallel. The management of the batteries and the calculation of the power data are executed autonomously. Visitors can experience the mBMS at the Hanover fair from April 26 to 26 in hall 13, booth C16 – at the joint booth of Bayern Innovativ.

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