STMicroelectronics AEK-POW-BMS63EN User Manual

Getting started with the AEK-POW-BMS63EN battery management system
Introduction
In a multicell battery pack, placing cells in series augments the possibilities of cell imbalance, which equates to a slower but
persistent degradation of the battery.
There are always slight differences in the state of charge (SOC), self-discharge rate, capacity, impedance, and temperature
characteristics, even for cells of the same model from the same manufacturer and even from the same batch of production.
These differences can lead to a divergence in a battery cell voltage over time. Cells with lower capacity or higher internal
impedance tend to have higher voltage than the rest of the series cells at full charge. These cells are weakened further by
continuous overcharge cycles. The higher voltage of weak cells at charge completion causes accelerated capacity degradation.
On the other hand, in discharge, the weak cells tend to have lower voltage than the other cells, due to either higher internal
resistance or the faster rate of discharge that results from their smaller capacity. This means that if any of the weak cells hits the
cell undervoltage-protection limit while the pack voltage is still sufficient to power the system, the full capacity of the battery is
not used.
One of the emerging technologies for enhancing battery safety and extending battery life is advanced cell balancing. Since
new cell balancing technologies track the amount of balancing needed by individual cells, the usable life of battery packs is
increased, and overall battery safety is enhanced.
A battery management system (BMS) can manage battery cells, enhancing their safety and duration.
A BMS combines hardware and software to monitor and send acquired data to a dedicated device to protect the battery from
overload or over discharge, lengthening its life cycle.
In the earlier BMSs, the SOC estimation was based only on the voltage reading.
Nowadays, instead, this estimation is based on Kalman filters, which provide more accurate data on the SOC by reading the
voltage, the current, and the temperature of battery cells.
The modern BMS includes functions such as cell monitoring, balancing, safety and protection of the batteries, the state of
charge estimation and thermal management:
• Cell monitoring: this function is based on the acquisition of the current, the voltage, and the temperature of each cell of
the battery pack.
• Cell balancing: consists of distributing the energy and maintaining the SOC of the cells at a similar level. There are two
different types of balancing: active and passive. Active balancing consists of transferring the exceeding energy of cells
with a higher SOC to cells with a lower SOC to reach the same level. Passive balancing dissipates the exceeding energy
of cells with a higher SOC, generating heat. Cell balancing is a key function to maintain the battery capacity and lengthen
its duration.
• Battery safety and protection: a BMS ensures that the battery works in safe conditions for the users and the battery itself.
• State of charge (SOC) and state of health (SOH): an accurate SOC estimation is necessary to lengthen the battery life
cycle, prevent battery damage, and ensure efficiency and accurate calculations of the SOH and cell balancing.
Our AEK-POW-BMS63EN is a battery management system (BMS) evaluation board that can handle from 1 to 31 Li-ion battery
nodes. Each battery node manages from 4 to 14 battery cells, for a voltage range between 48 V and 800 V.
The board is based on the L9963E, which is designed for operation in both hybrid (HE) and full electric (BE) vehicles using
lithium battery packs, but its use can be extended to other Transportation and Industrial applications.
The L9963E is an ASIL-D, AEC-Q1000 qualified device, compliant with ISO26262.
The main activity of the L9963E is monitoring cells and battery node status 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. Measurement data are available for an external microcontroller to
perform charge balancing and to compute the state of charge (SOC) and the state of health (SOH).
The AEK-POW-BMS63EN can measure 5 values of temperature through 5 GPIOs (which can be configured as analog inputs to
connect NTCs).
UM3185 - Rev 1 - May 2023
For further information contact your local STMicroelectronics sales office.
(BMS) evaluation board based on the L9963E
UM3185
User manual
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