Electric Vehicle Battery Management System

Electrical vehicle (EV) batteries must operate in a controlled, optimized manner to function in a way that maximizes battery longevity and performance while reducing safety risks for users.

That’s why electric vehicles have battery management systems (BMS), which serve as the brains of the batteries managing and monitoring charging and discharging for safe and efficient operation of the battery pack.

What is an EV battery management system?

A BMS is an electrical system that is part of an overall EV power management system, which manages and optimizes the distribution and utilization of electrical power within electric cars. An EV power battery management system typically includes the following components:

  • Sensors to measure voltage, temperature, and current
  • A microcontroller or processor to analyze sensor data and execute based on intelligent algorithms
  • Communication protocols, such as control area network (CAN) bus, which enable the reliable, efficient exchange of data with the electric car’s control systems
  • Balancing circuit hardware to equalize the voltage and state of charge (SOC) of individual cells within a battery pack, known as cell balancing
  • Power supply which provides electricity to the BMS components
Note that the battery packs consist of battery cells connected together into battery modules along with the battery management system, cooling system and other electrical components all contained in an enclosure.

Functions of EV battery management systems:

Battery management systems perform important functions that optimize battery life, operation and safety. Some key functions include:

Balancing and monitoring battery cells

A BMS measures the voltage and temperature of individual cells or groups of cells to ensure they are within safe operating limits. A BMS prevents overcharging and discharging by making sure cells in battery packs are balanced, meaning they have the same SOC, or remaining charge, in the battery. Overcharging or over-discharging cells could lead to damage and overheating. Rapid and uncontrollable increases in temperature may result in thermal runaway and fires or explosions. Battery management systems keep careful watch over battery state of health (SOH) to assess the overall condition and battery capacity over time, and state of power (SOP) to determine the available power output. Keeping voltage and temperature in check and carefully monitoring cells not only reduces safety risks but also helps optimize battery performance and life.

Safety management

A BMS is ready to take action if it finds the battery is being charged or discharged beyond its safe voltage limits. For example, it can employ cooling or heating systems to maintain optimal temperature ranges and shut down the battery in the face of excess heat. It can also limit currents to safe levels and even disconnect from circuits if needed. It can communicate with individual cells and sensors within the battery pack internally and with the vehicle’s control unit and other systems externally to provide status updates and receive commands. For example, the BMS can alert the user or the vehicle’s control system through warning lights or messages, indicating an overcurrent or overtemperature condition. By continuously monitoring setting and enforcing safe thresholds and taking immediate protective actions when these boundaries are exceeded, a BMS ensures the safety, reliability, and longevity of the battery pack and the overall system it supports.

Data logging

The BMS records data such as charge and discharge cycles, temperature profiles and fault conditions for analysis and maintenance purposes such as allowing for the identification and troubleshooting of recurring issues. For instance, the BMS can perform diagnostics to determine the cause of the overcurrent condition, whether it is due to a fault in the battery pack, the load, or an external charging system.

Without a battery management system, critical issues could arise, leading to serious consequences for both the vehicle and its users. Excessive currents and voltages during charging or discharging could damage the battery cells or cause short circuits, posing significant safety hazards. Unbalanced cells could lead to uneven wear and tear, reducing the overall lifespan of the battery pack. Continuous exposure to suboptimal temperature conditions accelerates the degradation of battery cells. Without a BMS, the vehicle cannot accurately estimate the SOC, SOH or SOP leading to unreliable performance metrics and potential unexpected power losses. Operational problems like inconsistent power delivery and an inability to communicate with other systems would also result. A lack of fault detection and preventative measures would also lead to a variety of maintenance and reliability issues.

In short, a BMS is essential for ensuring the safety, efficiency, and resilience of an EV’s battery system.

Battery management systems on EV charging sites

Battery management systems also play an important role in commercial battery energy storage systems (BESS) on EV charging sites. In the face of increasing power needs amid energy market price volatility, limited grid capacity, and misalignment between onsite solar production and EV charging, charge point operators (CPOs) and fleet operators are choosing to add BESS to their charging sites.

Just like in EVs, a BMS helps manage and protect the battery packs used in these stationary commercial energy storage systems (ESS). The BMS works collaboratively with the site’s energy management system to ensure that the EV charging site operates efficiently, sustainably, and reliably. The BMS mainly focuses on the safety and optimal performance of the battery packs while the EMS manages the overall energy strategy for the site.

Sparkion commercial battery energy storage system.
The EMS can use the BESS to smooth out fluctuations in energy demand, providing a stable and reliable power supply to the EV chargers and other site operations while protecting against a site’s peak kilowatt usage. To do this effectively, the EMS must calculate how many kilowatt hours of stored energy are needed for this protection and for how long.

Every EV model has a unique onboard BMS, which manages a specific charging pattern. The charging site EMS needs to asses when vehicles are charging at high power. BMS data, such as battery SOC, is communicated to EMS to optimize how energy flows into the vehicles.

Lithium batteries start to charge at a slower rate as they approach 100% SOC. For example, a Tesla Model 3 Long Range charges at 192 kW when it only has 10% of range. However, once the battery is charged to 30% it drops down to 130 kW, then 88.5 kW at 50% and 45 kW at 80% SOC. A Model 3 typically charges in about seven minutes, with high power use only for four minutes (over 150 kW). Even if two Teslas arrive at 10% SOC at exactly the same time, the energy management system would only need to provide four minutes of energy to ensure the site’s demand charge doesn’t go above 150 kW, and seven minutes to keep the demand charge below a multiple of 130 kW. When looking at it from this viewpoint, an energy storage system can make a huge impact just by protecting a site’s max kilowatts for a small period of time.

Tesla EV charging rates
Sparkion’s EMS technology simultaneously matches energy storage support with the needs of the site at a specific time by leveraging Open Charge Point Interface (OCPI) data from the EV chargers, which are getting a live feed from the vehicle to understand what capacity to use for charging.

Battery management systems and second-life batteries

As demand for EVs grows, more batteries and critical raw materials will be required. Supplies of new batteries will not be adequate to meet market needs, potentially halting progress toward future sustainability.

However, used EV batteries still maintain 70-80% of their battery capacity. Using second-life EV batteries in your commercial BESS can add additional value for charge point operators.

Rather than using more new batteries, recycling EV batteries into a BESS reduces waste and prevents additional Earth mineral depletion, enhancing your sustainability efforts and economics. Pairing your BESS with onsite clean energy can even further your impact.

Battery demand and second-life EV battery supply.

Second-life lithium-ion battery supply could surpass 200 GWh per year by 2030. Repurposed EV batteries can qualify for green incentives, grants or rebates. These financial incentives can lower the overall cost of implementing and operating a BESS. Repurposed batteries also comply with regulatory requirements related to waste reduction and energy efficiency

Still, second-life storage solutions come with challenges. Second-life batteries often have different thermal characteristics, cells with different degradation levels due to varying usage histories and more sensitivity to overcharging and discharging. As cells age, their capacities and internal resistances can vary widely, which can lead to uneven wear that could jeopardize the overall life of the battery pack. Second-life batteries must be properly managed continuously to function optimally in their new roles in stationary energy storage or grid support and adhere to safety standards and regulations.

That’s why a good battery management system is essential for ensuring the safety, reliability, performance, and longevity of second-life batteries. By managing and monitoring the diverse and potentially degraded cells in these batteries, the BMS helps mitigate risks, optimize usage, and extend the economic and functional viability of second-life battery packs.

However, not all battery management systems can provide the same value from second-life batteries. Typically, in a conventional EV battery storage unit, the weakest cell drags down the usable capacity of the entire battery pack, decreasing economic efficiency.

Sparkion’s roots are in battery storage hardware. Sparkion offers a smart storage system powered by multi-protocol battery management system software that uses dedicated circuits and embedded algorithms to fully manage the energy input and output of each battery module independently, thereby maximizing the lifespan of each pack and the overall battery capacity. Sparkion’s proprietary SparkSwitch technology incorporated into its battery management system allows bypassing weak cells to generate more energy per cycle to reduce the BESS cost-per-kWh by as much as 60% while cutting CapEx cost to half of competitive solutions. The weakest cell only affects the specific battery modules and not the entire pack. This technology built into each of our Sparkion S1 battery module units results in a dynamic and cost-efficient storage that can adapt on the go to the evolving needs of EV charging sites.

Our vast experience with and deep understanding of electrical infrastructure also allowed us to design the SparkCore™, a better energy management system including software and controller. No matter the manufacturer, chemistry or state of health, Sparkion’s AI-driven battery management system solution can recycle EV batteries into energy storage systems for EV charging. The flexible, AI-driven SparkCore™ collects and analyzes site and other third-party grid and weather data using proprietary algorithms customized to operate according to the initiatives you’ve set for your business. SparkCore™ uses real-time monitoring to control the BESS and make the most out of battery storage across the site. In this way, Sparkion can maximize investments and minimize harmful effects on the environment with second-life EV batteries.

Additionally, auto manufacturers and fleets have a unique opportunity to repurpose their own batteries for EV charging to add economic and environmental benefits.

The Circular Second-Life Battery Cycle for Fleet Owners:

EV fleet owners reusing second life batteries.
Repurpose your own fleet’s batteries to reduce power costs and become energy resilient.
To summarize, using second-life batteries provides benefits including:
  • Meeting power demand
    Charging depots and enterprises from EVs to C&I to utilities and more are investing in energy storage to reduce operating costs and maintain vehicle uptime with cost-efficient, resilient energy.
  • Achieving maximum BESS investment
    Repurposing EV batteries in your BESS can provide even more value through reduced costs and more efficient EV charging. Fleet owners can significantly reduce energy and BESS costs by repurposing their inventory.
  • Furthering sustainability
    Repurposing retired EV batteries into a BESS reduces waste and prevents additional Earth mineral depletion, enhancing your sustainability efforts and economics. Pairing your BESS with onsite clean energy can even further your impact.

Want to learn more about Sparkion’s battery management system and second-life battery technology?