Devices that rely on lithium-based battery cells to operate will have battery management systems (BMS) installed into the packs. The BMS is designed to monitor the characteristics of the battery infrastructure to ensure safe operation.
If the battery cell experiences an issue, such as high temperatures or charging fluctuations, internal protection controls provide external communication to inform you about the state of the battery's health as well as prevent serious issues.
If the BMS is not designed correctly, the battery pack could experience overcharging, over-discharging, a loss in capacity, or damage. When designing a BMS, you need to take into account several key considerations to ensure that the BMS matches the battery pack's specifications and power needs to ensure optimal performance.
What is a Battery Management System?
Battery management systems play a crucial role in ensuring the safe and efficient operation of rechargeable battery packs. At Epec, our BMS is designed to provide continuous monitoring of key performance parameters during both charging and discharging. By utilizing real-time sensor data, our system tracks voltage, current, temperature, and state of charge to maintain optimal battery performance.>
Unlike many companies that rely on third-party solutions, we have developed our own advanced BMS technology, allowing us to maintain full control over system design and functionality. This integrated approach ensures a higher level of reliability and customization for each application.
Our cutting-edge BMS includes precise battery gauging, active cell balancing, built-in protection circuits, and intelligent system control firmware. Additionally, advanced safety features such as temperature-based charging restrictions prevent charging outside of safe operating conditions, enhancing both battery longevity and user safety.
Custom battery pack with battery management system.
System, Architecture, and Performance Design
BMS hardware is designed with microcontrollers, temperature sensors, communication interfaces, peripherals, power electronics, and firmware to operate. All these components work together to analyze the state of health (SoH) and state of charge (SoC) of the battery pack. The components also allow for cell balancing, will receive commands, and can report data to external devices. Based on the design of the BMS, it can help to improve and overall efficiency and performance of the cells by carefully regulating internal temperatures, preventing overcharging, undercharging, and over-discharging, and keeping the cells balanced during charging cycles.
Manufacturers who design battery packs will have their specifications and requirements for battery cell chemistry that will differ from other packs. Understanding the voltage and current needs of the device and selecting the appropriate cell chemistry will directly impact on how the BMS will be designed and how it can be used to boost cell efficiency and performance. For example, certain battery chemistries may run at a lower voltage rating than other types of cells. Due to this feature, the BMS will be designed to consider the changed charging parameters and may require other monitoring needs based on how the cells must perform to power the connected device.
In addition to the system requirements, the architecture of the battery pack will directly influence the manufacturing of the BMS. The overall capacity of the cells as well as how the cells are placed, such as in a series/parallel configuration or a centralized or distributed location, will change the available power of the battery pack, how it charges, and how it must be monitored.
There are several types of BMS available to accommodate the specific battery pack. You may decide on a centralized BMS to control all the battery cells at once, a distributed BMS system with multiple BMS units to offer failsafe protection, or a modular BMS configuration with individual units that are interconnected. You may also choose from a passive cell balancing BMS unit that redistributes excess charge between higher voltage and lower voltage batteries, or a passive cell balancing BMS that equalizes the charge between all cells during the discharging and charging phases.
Safety and Protection Requirements
The main function of the BMS is to monitor cells to ensure safe operation during charging and discharging. Depending on the device and the environment, the battery pack may experience shocks, vibrations, power fluctuations, humidity, and excessive operating temperatures. Evaluating the working conditions of the device can ensure that the manufacturer installs the necessary safety features, protection circuitry, and enclosures for the BMS and battery pack.
When designing a BMS, various sensors are employed to monitor voltage, current, and temperature. With set parameters based on the battery chemistry requirements, the BMS continuously checks the battery cells and gathers data that can be used to ensure the correct voltage and current, troubleshoot possible performance issues, and maintain power accuracy while deploying controls to regulate internal temperatures.
Thermal Management Requirements
Every device has its unique power requirements and will operate in a range of environments and temperatures. These factors need to be considered when designing the system and architecture of the BMS. If external heating or cooling methods are not used where the battery pack will operate, engineers may design the BMS to control heating and cooling systems to maintain the appropriate internal temperatures.
Special considerations will have to be implemented when heating the battery pack in extremely cold working conditions. To prevent damage and loss of capacity, the BMS may be designed to control systems to draw heat from external sources or to draw the heat from the primary pack itself. The battery pack may also be designed to have coolant pumped into the enclosure when a thermal-hydraulic system has been put into use.
In other circumstances, the batteries may be exposed to heat from external environments, internal components, and from the cells themselves while running to power devices. This heat may become excessive to the point where thermal runaway can occur. Added safety measures, such as shutdown controls or allowing the BMS to open and close valves to disperse the heat, may be designed into the unit.
Costs and Commercial Factors
Design costs will be based on the types of functions you require for the BMS. These costs will increase based on the added installation of power supply features, firmware, sensor data, protection circuits, microcontroller units, and communication interfaces.
For devices with power requirements that have long been established within that particular industry or operate using simple parameters, system and architecture costs may be controlled using off-the-shelf BMS. These units can help speed up time-to-market deadlines yet have feature limitations when you require more sophisticated monitoring options. Another way to control costs may involve taking an off-the-shelf BMS and installing additional features. However, keep in mind that limited space may be available where not all the desired features can be placed into the unit.
Custom BMS units offer you the most control when it comes to acquiring the desired safety and protection features to optimize battery performance. The size of the BMS is only limited by the size of the device and the available budget. This design avenue will be the more costly option yet will allow you to have access to the newest components out on the market for the unit.
Summary
Battery pack performance can become optimized with a BMS to improve the longevity of the cells while offering the best power options for the device. Evaluating the power needs of the device, the features that are desired, and your budget can help to narrow down the design choices to select the components that will provide a cost-effective BMS unit.
Key Takeaways
- BMS ensures battery safety and efficiency: A well-designed battery management system (BMS) monitors key parameters such as voltage, current, temperature, and state of charge to prevent issues like overcharging, over-discharging, and overheating, ensuring optimal battery performance.
- Different BMS architectures suit different applications: Centralized, distributed, and modular BMS configurations offer varying levels of monitoring and control, while active and passive cell balancing methods help maintain consistent charge across battery cells.
- Thermal management is crucial for battery longevity: The BMS must regulate internal temperatures, preventing thermal runaway by using cooling, heating, or external thermal management systems, particularly in extreme environmental conditions.
- Safety features protect against environmental stressors: A BMS incorporates protection circuitry, sensors, and enclosure design to safeguard battery packs against vibrations, shocks, power fluctuations, and exposure to heat or humidity.
- Cost considerations impact BMS design: Off-the-shelf BMS units can reduce costs and speed up production but may lack advanced features, whereas custom BMS solutions provide greater flexibility and safety but require a higher investment.
