The Advanced Automotive Battery Conference (AABC) oragnised in Pasadena, California, 4-8 February 2013 featured a session on battery design and BMS improvements. Chaired by Steven Clark, Senior Manager Energy Storage & HV Systems, Chrysler Group LLC. cars21.com provides a summary of the presentations in this third update from AABC 2013.
Improvements in BMS, today and tomorrow
According to Uwe Wiedemann, Product Manager Battery Systems Engineering and Technology, AVL, BMS architecture will change as a result of the following improvements:
- Low-cost communication for HV to LV system communication
- Highly integrated system ICS for cell voltage measurement and balancing function including ISO 26262 safety support
- Simplified contact system for cell to electronic interface
- Multipurpose smart module controller for < 60V systems
- Mechanical contactors replaced by smart electronic switches
- Low cost current measurement system
According to AVL, BMS will also become more important in the data they monitor, going from SoC/SoH/SoF and thermal behavior calculations to detecting early cell failures and monitoring mid-term life of the battery.
The limits of the 12V batteries
According to Magna Steyr, the current 12V battery will disappear, but not only due to PHEVs and BEVs. Indeed, conventional cars released on the market have seen a continuous increase in electrical power demand, driving the current 12V power supply to its limits. As a result European OEM’s are currently targeting a additional 48V vehicle power supply, mainly used for cranking and restarting an ICE, brake energy regeneration and electric and high power loads.
According to Magna Steyr, 48V systems will hit the market from 2016 onwards starting in the Premium segment.
Accurate measurements for cheaper batteries
Erik Soule, VP & GM Signal Conditioning Products at Linear Technology explained the need for measurement accuracy in battery management systems. Indeed, to guarantee minimum battery capacity, manufacturers have to rely on high voltage analog ICs that measure V, I & T.
According to Linear Technology, “low-cost” ICs can have an SoC estimation error of 10% when “precision” ICs have an SoC estimation error of 1%. This has important consequences for the cell cost in guaranteeing a minimum capacity. Savings up to $800 (€595) on the cell costs can be observed by using precision ICs instead of low-cost ICs (based on 562$/kWh (€418/kWh) cells).