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Understanding Battery Management System (BMS) – How It Works, Building Blocks, and Functions

When you step inside your electric car and switch it on, the cluster displays the distance you can go. You choose your pit brakes based on this range to reach your goal, but have you ever wondered how your car determines how far it can go?

The Battery Management System, often known as the BMS, monitors the battery pack that powers your electric car and calculates the range for you. The device also monitors the battery pack’s condition and guarantees its safety.

Lithium-Ion Cells and Battery Packs: An Overview

It’s crucial to comprehend how battery packs are manufactured before discussing Battery Management Systems.

A battery pack module is constructed of lithium-ion cells that are joined to one another to form an electric vehicle’s battery pack. To build a battery pack, further connections between these modules and other modules are made. This battery pack’s management is made easier and more serviceable thanks to the modular architecture. This design architecture enables the battery pack manufacturer to replace a damaged module as opposed to the entire battery pack.

A high power-to-weight ratio, excellent energy efficiency, low self-discharge characteristics, and strong high-temperature performance are just a few of the benefits that lithium-ion cells have to offer. Due to these qualities, lithium-ion cells are the preferred option for electric cars; nevertheless, these batteries are not without flaws, and solid-state battery technology is attempting to address these issues.

Another thing to keep in mind is that, when used within certain parameters, lithium-ion batteries can only provide the benefits indicated above. A summary of these operational constraints is provided below:

  • Voltage Requirements: Electric car battery packs are constructed using lithium-ion batteries. For context, consider that the Tesla Roadster has 6,831 cells, each of which must function within a specific voltage range. This range is often 3.0 to 4.1 volts for most cells. The battery pack’s lifespan and the performance it provides are reduced if the cells are utilized outside of these parameters.
  • Temperature Restrictions: Monitoring the temperature of lithium-ion batteries is necessary in addition to the voltage limitations. This range falls between -20 and 55 degrees Celsius for the majority of cells. The performance and longevity of the battery pack may be significantly reduced if the cells are operated outside of specified temperature ranges.
  • Current Draw: Monitoring the quantity of current being pulled from the cells is also necessary. The life of the cells shortens exponentially if the current taken from them exceeds the restrictions that are set.
  • Charging Current: Additionally, the battery pack must be watched while being charged. This is due to the rapid infusion of large quantities of electricity into the battery pack that often takes place during fast charging utilizing level 3 chargers. Because of the high current flow in the battery pack, the cells may overcharge, overheat, and lose life and efficiency.

A battery pack needs a Battery Management System because various variables must be maintained for it to operate at its best. A computerized system called the management system keeps track of a number of each cell’s properties and makes sure the battery pack runs within predetermined bounds.

Let’s dig into what is a Battery Management System?

The internal operating characteristics of temperature, voltage, and current are monitored and managed by a battery management system, or BMS, when a battery is being charged or drained. The BMS determines the State of Charge (SoC) and State of Health (SoH) of the battery to improve performance and safety. It guards against overcharging or over discharging the battery pack. By doing this, it keeps the charge level between the maximum and lowest permitted levels, preventing unexpected events like explosions. A BMS is therefore an essential tool for ensuring both the battery’s and the user’s safety.

Benefits of Battery Management Systems

  • Make sure the batteries run efficiently.
  • Monitoring battery status continuously to prevent an explosion.
  • Prolongs the life of the battery.
  • Shows battery level.

Battery Management System (BMS) Building Blocks

The four primary functional blocks are:

  • Cut-off FETs
  • Fuel Gauge Monitor
  • Cell voltage monitor
  • Temperature Monitor


Cut-off Field-effect transmitters (FETs): Connecting the battery pack’s high side and low side using a FET driver creates an isolation barrier between the battery and the charger.


Fuel Gauge Monitor: This helps to keep an eye on the charge that enters and leaves the battery pack. The quantity of charge flowing is calculated by multiplying current and time.

A 16-bit ADC with a low offset and high common-mode rating is used to measure the voltage of the sensing resistor, which is the most efficient and cost-effective method for monitoring current flow despite the fact that there are other methods. To achieve a wide dynamic range at a faster rate, a higher ADC is advantageous.


Cell Voltage Sensors: One may classify cell voltage monitoring as a standard feature of the battery management system. It may be used to assess the battery’s condition. To ensure safety and extend battery life, all cells in a battery should function at normal voltage levels when being charged and discharged.


Temperature Monitoring: As technology advances, batteries are designed to deliver large currents while maintaining a consistent voltage. Because batteries can unexpectedly explode due to a strong current flow forcing them to suddenly increase in temperature. It must be kept away from. To control the battery temperature to the rated value, the BMS continually monitors it.

It will alert you to start/stop charging or discharging if the temperature exceeds the rated value, this function is useful.


Other Building Blocks:

  • Battery Authentication- Blocks the BMS electronics from being connected to the external battery pack.
  • Real-Time Clock (RTC)- Used in black-box software.
  • Memory- Used in black-box software
  • Daisy Chain- Makes connecting stacked devices easier.


Battery Management System Working and Functions

A computer that is connected to several sensors is the Battery Management System. These sensors transmit data to the BMS about each cell’s voltage, current, and temperature.

After that, the Battery Management System examines this data to make sure that each cell is operating within the set parameters. If that isn’t the case, it tries to resolve the issue.

The BMS controls the cooling system to lower the battery pack’s temperature if the cells inside it get too hot. The Battery Management System balances the cells when there are changes in cell voltage. It transfers energy from one cell to another in order to balance the cells and guarantee that they are all running at the same voltage. The BMS also performs the actions mentioned above and logs the data it collects in order to assess the battery’s level of charge and overall health.

Functions of Battery Management Systems


Lithium-ion battery packs have a higher density, which raises the possibility of a fire. Therefore, as was already indicated, operating batteries at rated value is crucial.

This task is done for you by a BMS. It stops the battery pack from being overcharged or depleted to lengthen battery life.

Additionally, it protects short circuits, overcharging and over-discharging, anti-reverse charging, etc.

Modern BMS has Bluetooth and Universal Asynchronous Receiver-Transmitter (UART) connectivity capabilities.

Improvement of Battery Performance

A battery must function between the maximum and lowest rated values, i.e., current, voltage, temperature, etc., in order to work at its optimal level. A BMS aids batteries in operating within these crucial rated values, as we previously know.

It helps to guarantee uniform cell charging and discharge in the context of battery packs. As a result, the performance of the battery pack is substantially improved.

Along with improving performance, an effective battery management system helps to prolong the life of the battery packs.

Health Observation and Diagnostics

The amount of time needed to charge and discharge a battery depends on its degree of charge. A BMS can determine and display the amount of charge left in the battery.

By comparing these to the rated values, a BMS looks for anomalies in the battery parameter. Additionally, it has the ability to make adjustments to improve the battery’s health.

Final Thoughts

The cost, efficiency, and durability of any system must constantly be balanced in every design, though. Security is a single value that can never be underestimated. The BMS is unquestionably an undervalued component of an electric vehicle and requires the same consideration as the battery in terms of relevance and crew and vehicle safety.

Power plants, automobiles, electric vehicles, aviation, and other industries frequently employ battery packs. These rechargeable cells or battery packs are managed by battery management systems, which track the battery’s condition, compute secondary data, report that data, regulate its environment, authenticate it, and balance it. To protect the batteries from overcharging, blasting, and short-circuiting, it is essential to assess the protection features and dependability of the BMS.

eInfochips uses hardware-in-Loop technology for the Battery Management System Framework to assess and evaluate BMS functionality.

The framework can be used to test both linked items and apps.  For each test case added to test management, the framework creates a feature file, runs the test using created keywords, and then uploads all test results using the framework libraries. Hardware-in-the-loop test of BMS controllers, Real-time battery simulation in Simulink/Simscape, simulate battery voltage, capacity, and SOC parameters are some of the key features. To connect to our team of experts, click here.

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