AEK-POW-BMSLV [STMicroelectronics]

The AEK-POW-BMSLV is built with automotive-grade components, and it is able to connect to a battery pack and to monitor both state of charge (SOC) and state of health (SOH) of each battery.

It also manages battery balancing by passive discharge, thanks to the software already preloaded on the on-board SPC58EC80E5 microcontroller.

The AEK-POW-BMSLV has been specifically designed to manage the battery management system for low-voltage applications: applications whose voltage range is below 60 V, for example, motorcycles auxiliary power and electric bikes.

The versatile CAN2.0A/B protocol facilitates integration into several systems and efficient component communication.

The AEK-POW-BMSLV is equipped with two CAN ports for flexible networked connections, while four high-side channel outputs optimized power distribution.

The BMS adjusts to various battery configurations, supporting from 4 up to 14 series-connected cells.

It hosts the following devices: SPC58EC80E5, L9963E, L9963T, SPSB100 (customized version with CAN port), and VNQ7050AJ.

The SPC58EC80E5 automotive-grade microcontroller is responsible for calculating the SOC and the SOH of the battery pack connected, based on the measurement provided by the L9963E through the L9963T ISOSPI<>SPI transceiver.

The SPSB100 power mananagement integrated circuit (PMIC) has been integrated in this board as a customized version. This version features an embedded CAN-FD transceiver able to address and transmit the relevant information from the AEK-POW-BMSLV to an external domain control zone.

The VNQ7050AJ is used to drive contactors to disconnect the battery pack in case of maintenance or failure.

Thanks to the L9963T transceiver, the MCU and the L9963E communicate through the ISOSPI protocol, implementing differential communication for higher noise immunity. This is not strictly required considering it is a low voltage application but it opens the possibility for easy extension to the high voltage case.

The main activity of the L9963E is monitoring cells through stack voltage measurement, cell voltage measurement, temperature measurement, and coulomb counting. Measurement and diagnostic tasks can be executed either on demand or periodically, with a programmable cycle interval.

The main functions of a standard BMS are monitoring and protecting the battery pack. The protection function brings the system to a safe state in case of under/overvoltage and overheating.

Our board safety features include overload and overvoltage protection, against potential issues that could compromise battery integrity, alongside over-discharge protection to prevent excessive discharge and extend battery life.

AEK-POW-BMSLV core features ensure battery health and longevity. Continuous voltage monitoring provides real-time information about the battery status, enabling quick detection of deviations from ideal voltage levels, ensuring reliability, and preventing potential issues.

The AEK-POW-BMSLV provides an elaborate monitoring network to sense the voltage, current, and temperature of each cell. This sensing allows elaborating the SOC of each battery cell and, consequently, the state of charge of all battery packs.

The SOC allows assessing the remaining battery capacity. For maintenance reasons, it is important to monitor the SOC estimation over time.

According to our algorithm based on an extended Kalman filter for the SOC calculation, the more the SOC differs from its nominal value (that is, its value when the batteries are new), the more a cell of the battery pack risks overdischarge.

Thus, the SOC evolution over time allows asserting the state of health (SOH) of a cell or a battery pack to spot early indications that a cell is at risk of overdischarge or overcharging.

The SOC of a battery cell is required to maintain its safe operation during charge, discharge, and storage.

However, SOC cannot be measured directly and is estimated from other measurements and known parameters (such as characterization curves or look-up tables). This information on the battery cells is necessary to determine how the voltage varies according to the current, the temperature, etc., based on the battery chemical composition and production lot used.

In the AutoDevKit ecosystem, we developed a demo application based on the SPC58EC80E5 microcontroller, to estimate the SOC of 14 cells in a BMS node connected with an AEK-POW-BMSLV evaluation board.

The results of SOC estimation, cell voltage, battery pack temperatures and current can be printed via the serial port to a terminal on the PC with a speed rate of 115200 bps.

For further information about the preloaded algorithm on the board, please refer to UM3185.

• Low-voltage (<60V) single board for a complete battery management system (BMS)
• Hosts:
  • L9963E AEC-Q100 qualified automotive multicell battery monitoring and balancing IC
  • L9963T AEC-Q100 qualified automotive general-purpose SPI to isolated SPI bidirectional transceiver
• SPC58EC80E5 microcontroller automotive grade to perform charge balancing and to compute the state of charge (SOC) and the state of health (SOH)
• VNQ7050AJ quad channel high-side driver for battery pack contactor driving
• SPSB100 (custom version with CAN port) fully integrated power management system IC of which the following features have been implemented on the board:
  • CAN FD transceiver for external communication
• Additional external CAN transceiver
• SPI for external communication
• Configurable window watchdog
• System wake-up feature and ignition wake-up
• Fault collection control unit (FCCU) used to collect eventual issues raised by the micro and according to an implemented logic perform some actions like system shutdown
• Fail-safe diagnosis from SPSB100 to microcontroller
• Voltage and current monitoring of every single cell and of the entire battery node
• 8 GPIOs to connect temperature sensors as NTCs, of which four GPIOs wired to the microcontroller while the other four to the L9963E
• Passive balancing is executed through 100kΩ external resistors
• Dimensions: 145x65mm
• Included in the AutoDevKit ecosystem