Reference board eases design of 48V battery monitoring systems

September 14, 2015 // By Christoph Hammerschmidt
In hybrid-electric vehicles, the 48V supply is becoming the state-of-the-art to run high-current applications such as electric power steering, air conditioning or motor generators. A new reference from analog chip vendor ams AG facilitates the development of small yet high performance 48V battery monitoring systems.

The board is suitable for use in the next generation of single 48V lithium battery systems, and in dual 48V/12V battery systems, such as those used in passenger and light commercial vehicles and electric scooters and motorbikes. It provides a complete battery monitoring and safety system on a single, compact PCB. The board measures the flow of current through the battery, and the voltage and temperature both of the entire battery and of individual lithium cells.


The integrated high-side current sensor is connected to the battery’s positive terminal. This has enabled the vendor to include a battery disconnect switch on the board which is automatically actuated when the current sensor detects an overload condition. This protects the battery’s cells from damage and helps to prolong the life of the battery.


The board also implements an innovative method of cell balancing in hardware, without the intervention of a microcontroller or processor: The circuit compares the voltages of individual cells and switches the charge and discharge current between cells in order to maintain an equal voltage across all cells.


Because the entire 48V battery monitoring system operates without complex application software, it is quick and easy to implement in a vehicle’s power management system. It also makes it easier for power system designers to achieve compliance with the ISO 26262 functional safety standard, because it eliminates the need to develop, test and verify the safe functioning of complex algo-rithms for error compensation and cell balancing.


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