Importance of indigenous smart BMS for lithium-ion batteries in electric vehicles

At present, most Indian companies heavily rely on imported Battery Management Systems (BMS), especially from China. In this article, Ganesh Moorthi (CTO at Renon India) discusses the growing importance of the availability of indigenous smart BMS solutions.

Type of BMS and their respective capabilities

Depending on the amount of digitalization of the logic, the BMS is split into Analog BMS and Digital BMS categories. For ease, these are called Hardware BMS and Software BMS, respectively, in the industry.

Hardware BMS – The hardware BMS is basically a protection circuit that takes care of the upper and lower limits of voltage, current, and temperature parameters. These three parameters are the basic sensors that are present in any modern battery pack, which means that they are the three parameters being monitored in real time. Along with the protection, they are also involved in balancing the energy of each cell or string in series so that the pack is balanced enough not to have any weak cells or strings.

Software BMS – On the other hand, the software BMS is smart, and in addition to the protection and balancing functions, it can also estimate multiple states, such as the state of charge (SoC), the state of health (SoH), the state of energy (SoE), and the state of power (SoP). It can identify the type of load connected, collect data, support pre-discharge, store data, and drive other circuits, and most importantly, all of these are enabled through two-way communication via CAN or serial communication.

The need for indigenous Smart BMS

The Battery Management System plays three major critical roles.

– First, it takes care of the safety of the pack by acting as an automated switch that detaches the battery from the supply and load whenever unfavourable situations for the battery pack are encountered based on pre-defined logic.

– Second, it takes care of the efficiency of the pack by making sure that the battery pack is balanced. Generally, many cells are electrically joined in series or parallel to achieve the required voltage and capacity. As ‘Every Cell is Unique’ and ‘The battery pack is as good as the weakest cell’, balancing the pack to work at an optimal state is critical to the efficiency of the pack. This is called cell balancing, and they are majorly energy-losing or energy-sharing types.

– Third, the BMS takes care of the performance of the pack thanks to the advanced processor and logic circuits in the BMS, which enable the opportunistic charging or discharging of the battery pack.

In my opinion, as lithium-ion chemistry-based cells or any electrochemical cells are still evolving, the BMS should be smart enough to handle the unknowns to the point where at least the safety is not compromised. This is definitely the brain of the battery pack. Indigenization and localization of this hardware are very critical to the success of this mission.

Main reasons for the lack of BMS manufacturing in India 

A lack of BMS technology is likely to blame for India’s industrial shortfall in BMS. The firmware logic, a software layer beyond the micro-controller, and the analog front end are where the development of the battery management system reaches maturity and where it is differentiated from other similar systems. We need more firmware resources with expertise in hardware, software, and the market at large. This is the primary reason why only a few businesses choose to develop their own battery management systems. 

It also takes a long time to review and test the BMS for various test cases and failure modes, which is a significant determinant. The concern over ensuring the supply chain of the chipsets and other active components has been a significant factor in the reservation among EV firms in recent years.

Challenges and opportunities 

We are witnessing great excitement and growth in the Indian EV segment, with an increasing number of companies working on developing indigenous smart BMS. Yet, we have a long way to go before we can claim that we have built a self-reliant EV ecosystem in our country.

The critical components of the BMS are the Analog Front End (AFE), a functional electronics circuitry that interfaces with a variety of sensors, majorly voltage, current, and temperature sensors, microcontrollers, and switching circuits. 

Though the talent pool is available and building up in the country, the supply chain crisis still has a lot of impact on the effort toward localization. However, we are in the early stages of technology development, and a lot of advancements are still expected in the BMS technology itself, including wireless BMS, active balancing, fast charging enabler, circuit models for new chemistry cells, etc.

We are at the cusp of a massive transformation with industry-wide and government efforts. And this transition opens up a plethora of opportunities for Indian EV ecosystem players. It is to be noted that not one size fits all, and hence multiple variants and continuous research are needed. Thankfully, some Indian startups are filling this gap and are already working on developing smart BMS. There are next-generation BMSs that make up the core of the Li-ion battery packs developed indigenously by startups.

About the Author

Also Read: Why is a BMS needed in an electric vehicle?