ST AutoDevKit AEK-POW-BMS63EN User Manual

Getting started with AutoDevKit battery management system (BMS) evaluation
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.
We offer a variety of BMS evaluation boards (AEK-POW-BMS63EN, AEK-POW-BMSNOTX, AEK-POW-BMSWTX) to meet
various customers' needs and help designers build different types of BMS chain topologies fit for any end-user application.
These boards are included in the AutoDevKit ecosystem to make design and prototyping even faster and easier. Next chapters
focus on a comprehensive and detailed description of all the boards belonging to our BMS range and the various topologies of
BMS chains you can experimenting with.
Note: The evaluation boards described in this user manual are designed for R&D laboratory use only. They are not
intended for field use in vehicles.
Moreover, they are not reference designs. Their purpose is evaluation and not production as stated in our
of use.
UM3185 - Rev 3 - August 2024
For further information contact your local STMicroelectronics sales office.
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