11th February 2022

An Overview of the Analog Front-End of the BMS

(L) FS-XT-BMU;  (R) FS-LT

Introduction

Functional blocks of the BMS (Battery Management System) comprises a control block which is the Microcontroller (MCU) and a sensing block, which is the Analog front end (AFE).

Let’s delve deeper into the Analog front end (AFE) block of ION’s BMS!

The Analog Front-end (AFE)

The AFE is an Integrated Circuit (IC) in the BMS, which is designed to wrap all the analog circuitry required for the design and operation of a BMS system up into a small package. It contains inputs to measure the cell voltages of each cell position in the cell stack. The AFE can measure 3 to 15 series cells in a battery pack in a 0-5V range.

AFE also plays a significant role in triggering the balancing circuitry. The AFE IC contains an in-built temperature sensor which is meant for measuring the BMS board temperature. The AFE has an internal small digital state machine that manages the sequential measurement of voltages present at the input to IC, along with providing the I2C interface.

 Click on the image to enlarge.

The features of an AFE include:

  • Measuring each cell voltage and setting it to MCU
  • Measuring temperature (usually via NTC thermistor)
  • Balancing circuitry for each cell

Essential functional blocks of the BMS connected to the AFE

AFE is connected to multiple functional blocks, such as:

  1. Voltage Sensing Channel
  2. Temperature Sensor
  3. GPIO Connectors
  4. Balancing
  5. ISO-SPI Channel
  6. Analog Filtering
  7. PSU AFE

1. Voltage Sensing Channel

The voltage sensing channel takes the readings from the individual cells in the pack and sends it to the AFE. It also acts as a channel for balancing the cell.

2. Temperature Sensor

NTC thermistor temperature sensors are a key component in Li-Ion battery safety. They provide critical temperature data required to keep the Li-Ion battery in the optimum condition during the charging/discharging cycle. The temperature sensor will be placed in the hotspot of the battery pack, which measures temperature in the form of voltage and the data will be sent to the AFE.

3. Balancing

When there is an imbalance between the cell in a pack that occurs over a prescribed limit, the AFE will give a triggering signal which is controlled by MCU to the balancing circuit in the BMS.

4. GPIO Connectors

GPIO connectors give the provision of connecting extra functions to the BMS like cooling system, contactor control, heating system, Ignition, sensors, etc. Enabling this functionality is done by making changes in the firmware.

5. ISO-SPI Channel

ISO-SPI channel is meant for internal communication between slave(sensor circuit) and the master(control circuit). This is also known as the internal CAN communication channel.

6. Analog Filtering

It filters electrical noises in voltage and temperature measurements.

7. PSU AFE

It represents the power supply unit required for the functioning of AFE. Usually, it is tapped from the cell stack.

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Electric 2 & 3 wheelers such as scooters and rickshaws have complex use-cases that require smarter management of their batteries. ION Energy’s automotive-grade battery management systems have been designed to meet the requirements of next-generation electric two and three-wheelers.

Learn how ION Energy can help you build a high-performing e-scooter/rickshaw battery pack with long-lasting battery life.

About ION Energy

ION Energy is an advanced battery management and intelligence platform. We’re focused on building technologies that improve the life and performance of lithium-ion batteries that power electric vehicles and energy storage systems.

Our customers typically choose ION Energy because of its reliability, transparency, commitment towards customer success, and innovative business models. OEMs and battery pack manufacturers across the globe choose ION’s integrated battery management solutions to continuously improve the life and performance of the battery.

Also read: Maxwell gets accredited with ISO 9001:2015 Certification

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