battery management system

In the push towards sustainable transportation, the crucial role of electric vehicle batteries stands tall. Yet, what controls these powerhouses ensuring safety, efficiency, and durability? Here’s where the Battery Management System for electric vehicle takes center stage, working its magic discreetly. 

Electric Vehicle Batteries: Types, Performance, and Efficiency

The electric vehicle (EV) revolution is not just about sleek car designs and silent drives; the true essence lies beneath – the batteries. Today’s EVs, whether they are hybrid, plug-in hybrid, or all-electric, rely heavily on battery packs. 

The battery used in your vehicle depends largely on its type. Interestingly, current battery packs are built to outlive the vehicles they power, with warranties generally spanning 8 years or 100,000 miles. Under optimal conditions in moderate climates, some of these batteries can serve for up to 15 years.

Lithium-Ion Batteries

Predominantly found in today’s EVs, these batteries are also integral to everyday devices like smartphones and laptops. Known for their high power-to-weight ratio, they ensure efficiency, excellent performance in elevated temperatures, and stability in holding a charge. 

They are recyclable, but their production often involves ecologically concerning methods, like using half a million gallons of water to refine a ton of lithium.

Nickel-Metal Hydride Batteries

These are primarily present in hybrid vehicles, which employ both electric motors and gasoline engines. The gasoline component is used to recharge the battery. 

These batteries often outlast their lithium-ion counterparts and are safe. Yet, they are not without drawbacks. They’re expensive to manufacture, generate considerable heat at elevated temperatures, and come with a high discharge rate.

Lead-Acid Batteries

These are the conventional 12-volt batteries employed in gasoline vehicles to kick-start the engine. Having been around for ages, they are both cost-effective and reliable. However, their usage in EVs is limited to powering auxiliary features like safety measures, brake boosting, and power steering due to their short lifespan and limited performance in colder climates.


These devices serve as supplementary storage solutions, helping in balancing the load on lithium-ion battery packs. Ultracapacitors use a polarized liquid situated between an electrode and an electrolyte, offering a power surge during acceleration in EVs.

Solid-State Battery

Gearing up to possibly become the favored choice for EVs in the near future, these batteries are projected to curtail the carbon footprint by an astounding 40%

Opting for solid ceramic materials rather than liquid electrolytes for electric conduction results in various benefits. Not only are they lighter and cheaper, but they also promise faster charging speeds. 

Major automotive players like BMW and Ford are rigorously testing these for potential integration by 2025. A remarkable feature is their ability to provide a driving range of up to 500 miles, addressing the prevalent “range anxiety” issue.

Ultimately, EV batteries are evolving at an unprecedented rate, with each type offering unique benefits and features. As the automotive world shifts towards sustainable solutions, it’s fundamental to understand these technologies, as they will shape the future of mobility.

EV BMS: What It Is, What It Does, and Why It’s the “Brain” of the Battery

What is the EV Battery Management System?

The central part of any electric vehicle is its battery, a complex arrangement of cells working in harmony to power the vehicle’s systems. Much like how our body has a nervous system overseeing its functions, an EV’s battery requires a guiding force: the Battery Management System (BMS). 

At its core, the BMS is an intricate technology that supervises and manages the battery pack. This battery pack isn’t just a single entity, but a collective of battery cells, organized in a matrix, designed to deliver a specific voltage and current for a predetermined time.

But how does a BMS adapt to different battery sizes, complexities, and requirements? 

The answer lies in its architecture. There are diverse BMS topologies, tailored for varied applications and needs. The Centralized BMS, for instance, features a singular, primary BMS directly connected to all battery packages. It’s compact and cost-effective, yet it comes with its set of challenges in troubleshooting due to extensive wiring.

On the other end of the spectrum, there’s the Distributed BMS, where each battery cell or module has its own dedicated BMS board, simplifying wiring but complicating maintenance. Other architectures like the Modular BMS and Primary/Subordinate BMS find their unique positions between these extremes, balancing cost, functionality, and ease of maintenance.

Regardless of the chosen topology, the overarching goal remains the same: to safeguard the battery. By understanding and selecting the right BMS architecture, EVs can optimize performance, extend battery life, and ensure safe operations. As the electric revolution gains momentum, the EV BMS will undoubtedly play an instrumental role in shaping the future of transportation.

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What exactly does the EV BMS do?

Building on the importance of the EV BMS in shaping the future of transportation, it’s essential to delve deeper into its specific roles and responsibilities. 

At the intersection of innovation and safety in electric vehicles lies the EV Battery Management System. While many appreciate the efficiency and eco-friendliness of EVs, few recognize the silent sentinel ensuring that these vehicles run smoothly and safely: the BMS. By regulating the very lifeblood of an EV, its battery, the BMS takes on a role much like the brain in the human body.

Consider the high energy density of lithium-ion systems, which, while advantageous, leaves very little margin for error in management. The intricate nuances of battery management are handled by the EV BMS, ensuring not just efficient performance but also emphasizing functional safety. 

For instance, during both charging and discharging, the BMS is ever-watchful, making sure that parameters like voltage, current, and temperature remain within safe boundaries. If any cell or module goes beyond these set Safe Operating Area (SOA) limits, it could compromise the expensive battery pack or even lead to dangerous thermal runaway conditions. 

The stakes are high. A low-voltage state could induce copper dendrites to form on the anode, causing elevated self-discharge rates and raising safety concerns. Hence, the role of the BMS is not just managerial but also protective.

Now, think about performance, the second most critical facet of an EV BMS. The entirety of the battery pack’s efficiency hinges on optimal electrical and thermal management. For instance, balancing cells in a pack ensures that the State of Charge (SOC) remains uniform across them. This not only optimizes the battery capacity but also thwarts the degradation of cells and minimizes potential hotspots that can arise from overcharging weaker cells. 

Also, given that electrochemical processes in batteries are temperature-sensitive, a BMS sometimes activates external heaters or in-built heater plates, ensuring that lithium-ion cells are used within a favorable temperature range. Without this sort of rigorous temperature regulation, lithium-ion cells would face numerous challenges, including reduced performance during cold conditions.

But why liken the BMS to the brain? Because like our brain, which oversees and coordinates all bodily functions, the BMS is the central control unit of the EV’s battery. An entire Battery Energy Storage System (BESS) could comprise thousands of cells. Mismanagement, especially in high-voltage packs, can be catastrophic. Thus, the BMS is indispensable for ensuring safe operation.

Functions and features of a BMS

Electric vehicles have significantly advanced in recent years, providing an eco-friendly alternative to conventional gasoline-powered vehicles. Central to the functioning of an EV is the battery and, more critically, the EV battery management system (BMS) that oversees its optimal operation. 

The EV BMS enhances the safety and efficacy of the battery, ensuring longevity and efficient performance. So let’s explore the functions and features of the EV battery management system.

Monitoring Battery Parameters

A cornerstone function of a BMS in electric vehicle is to monitor various battery parameters. Key among them are:

  • Voltage: Reveals vital details like the total battery voltage, individual cell voltages, and the maximum and minimum voltages.
  • Temperature: Captures data on average cell temperature, coolant intake, coolant outflow, and the overall battery temperature.
  • State of Charge: Indicates the battery’s present charge level.
  • State of Health: Reflects the current battery capacity as a percentage of its original capacity.
  • State of Power: Highlights available power based on current usage, temperature, and other influencing factors.
  • State of Safety: Ascertains if the cell’s usage might pose any hazards by collectively analyzing all the mentioned parameters.
  • Coolant Flow: Monitors the speed and flow of the coolant.
  • Current Flow: Observes the current that enters and exits the cell.

Thermal Management

A significant factor that influences battery performance and lifespan is temperature. The battery management system for electric vehicle supervises and manages the battery’s thermal conditions. Systems may either be passive or active, and the cooling medium chosen can range from non-corrosive liquids, air, or phase change mechanisms. 

Air-based systems, although simpler, are less efficient and may lead to increased vehicular weight. In contrast, liquid-cooled systems offer better thermal conductivity, however they can introduce temperature discrepancies within the EV BMS.

Essential Calculations

The battery management system for electric vehicle performs a series of calculations to guide battery usage. This includes:

  • Determining energy in kWh since the last charge.
  • Measuring the internal impedance for gauging the cell’s open-circuit voltage.
  • Computing the charge in Ampere-hour to ascertain cell efficiency.
  • Tracking the total energy dispensed and the operational duration since the battery’s inception.
  • Logging the number of charge-discharge cycles.

Communication – Both Internal and External

The BMS in electric vehicle is equipped to communicate at both a cellular (internal) and external level. 

External communications, which vary based on the connected device’s complexity, can be executed through diverse mediums like serial communications, CAN bus (common in vehicles), DC-BUS communications, and various wireless channels. 

Internal communications, on the other hand, are typically seen in high-voltage BMS setups. Distributed BMSs need low-level internal cell controllers. The intricacies of these communications, especially in high-voltage systems, can be challenging due to voltage discrepancies across cells. Such challenges require solutions like optical isolators or wireless channels.

Drawing it all together, the BMS is the guardian of an EV’s battery, ensuring it operates optimally, remains safe, and contributes to the vehicle’s overall performance. It maintains the state of the battery, preventing overcharging or discharging, and keeps a real-time check on parameters like voltage, current, and temperature. 

Such systems underscore the thrust towards sustainable energy and the electrification of mobility. The battery management system for electric vehicle, without a doubt, stands as an unsung hero in our drive toward a greener future.

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BMS in Sustainability and Circular Economy

EV Battery management systems are critical components in the push towards sustainable electric vehicles. As we transition into a circular economy, advancements in EV BMS technologies play a significant role in ensuring the optimal performance and longevity of batteries.

One groundbreaking innovation is the introduction of the sensor-on-chip. Traditionally, state estimation, fault prognosis, and health diagnosis of batteries depend heavily on diverse battery parameters, which require a range of sensors. 

By integrating these sensors onto a single chip – termed sensor-on-chip – battery management system for electric vehicle becomes more compact. Specifically, on-chip thermal sensors, mounted on or within batteries, form a wireless sensor network that manages battery temperature both externally and internally. This technological direction promises a smarter BMS for EV batteries, significantly enhancing efficiency and performance.

The realm of smart power electronics is also experiencing significant advancements. Traditional energy conversion systems kept power electronics and BMSs separate. 

However, due to the progress in wide bandgap semiconductors and microcontrollers, future power electronics will integrate battery management directly. Such integration means that functions like battery cell balancing and thermal management could be achieved solely by power converters. These intelligent power electronics will not only improve reliability but will also enhance the intellectual management of EVs.

An important step towards sustainability is the Vehicular Information and Energy Internet (VIEI). This concept promotes the exchange of information and energy among EVs, reducing the dependency on local batteries and BMSs. The resultant vehicular network would be a part of an Internet of Things ecosystem, facilitating collaborative autonomous driving and transforming transportation systems. 

In this networked environment, EV batteries and BMSs will have evolved functionalities that encompass data, energy, and human interaction. However, as the VIEI becomes more intertwined with our digital lives, security, and privacy challenges arise, necessitating the development of advanced technologies like blockchain, cloud computing, and artificial intelligence to ensure a smarter and safer VIEI.

So as we edge closer to a sustainable and circular economy, innovative EV BMS technologies will undoubtedly be at the forefront, ensuring that EVs not only remain efficient but also evolve into smart, interconnected transportation tools.


The pathway of electric vehicles is one of innovation and evolution, and central to this is the BMS. As technology develops, so does the complexity of the battery management system for electric vehicle, ensuring EVs remain not just viable but exemplary symbols of green transportation.

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