Industrial equipment powered by rechargeable batteries needs more than a battery pack and charger. Operators should be able to monitor what's happening inside the battery and respond when operating conditions move outside acceptable limits.
That's where a battery management system (BMS) comes in.
A BMS monitors parameters such as voltage, current, and temperature to help protect the battery and manage its operation. Depending on the system, it can also estimate available charge, balance individual cells, communicate with other equipment, and provide diagnostic information.
For engineers, the BMS plays an important role in how the battery, charger, and equipment work together as a complete power system.
A battery management system is an electronic system that monitors and manages a rechargeable battery or battery pack.
Think of the BMS as the battery pack's monitoring and control layer. It collects information from the battery and uses that data to determine whether the system is operating within its established parameters.
Depending on the application and BMS design, the system may monitor:
The BMS can use these measurements to manage battery operation, trigger protective actions, and communicate battery status to other parts of the equipment.
A BMS combines monitoring hardware, sensors, control electronics, and software to continuously evaluate battery conditions.
During operation, the BMS measures conditions within the battery pack and compares them against predetermined limits. When a measurement falls outside those limits, the system can take an appropriate action.
For example, if the battery becomes too hot or an individual cell reaches an unacceptable voltage, the BMS may limit charging or discharging, communicate a fault, or disconnect the battery.
A BMS doesn't just collect battery data. It uses that information to help keep the battery within its intended operating limits.
Several functions make this possible:
Voltage is one of the primary measurements used by a BMS.
In a battery pack containing multiple cells, measuring only total pack voltage may not provide enough information. Individual cells can behave differently, even when they're part of the same pack.
A BMS can monitor individual cell voltages as well as overall pack voltage. This helps identify when a cell is approaching its upper or lower operating limit and provides data for other functions, including state-of-charge calculations and cell balancing.
The BMS can also monitor the current flowing into and out of the battery.
Current measurements show how quickly the battery is charging or discharging. They can also help the system identify conditions that exceed the battery pack's allowable current.
Tracking current over time can contribute to SOC calculations by helping the system estimate how much charge has entered or left the battery.
Battery performance and operating limits can change with temperature, making thermal monitoring another important BMS function.
Temperature sensors placed throughout the battery pack can monitor cell and pack conditions. If temperatures move outside established limits, the BMS can initiate a protective response.
Temperature can affect battery safety, charging behavior, performance, and service life.
That's especially relevant for industrial equipment operating outdoors, around heat-generating machinery, or across a wide range of ambient temperatures.
Monitoring voltage, current, and temperature gives the BMS the information needed to identify potentially damaging operating conditions.
Depending on its design, a BMS may provide protection against:
When the BMS detects one of these conditions, its response depends on the battery and equipment design. The system might limit operation, communicate a fault, stop charging or discharging, or disconnect the battery.
A Li-ion battery management system has an especially important role because lithium-ion cells need to remain within specified voltage, current, and temperature limits.
Industrial lithium-ion batteries commonly combine multiple cells to achieve the voltage and capacity required by the equipment. However, individual cells within a pack don't always behave identically.
Differences in manufacturing, temperature, use, and aging can cause cells to develop different characteristics over time. One cell may reach its operating limit before the rest of the pack.
Cell-level monitoring helps the BMS identify and manage these differences.
What is Cell Balancing? |
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Cell balancing helps manage differences in state of charge between individual cells in a battery pack. As the battery repeatedly charges and discharges, small variations can develop between cells. A BMS with balancing capabilities can help reduce these differences so the cells remain more closely matched. The goal is to prevent an individual cell from unnecessarily limiting the usable performance of the entire battery pack. The appropriate balancing method depends on the battery architecture and application requirements. |
One of the most useful pieces of information a battery management system can provide is state of charge.
SOC estimates how much usable charge remains in the battery. It's similar to a fuel gauge, but calculating the remaining energy in a battery can be more complex than simply measuring voltage.
Depending on the system, a BMS may use voltage, current, temperature, battery characteristics, and operating history to estimate SOC.
This information can help industrial equipment determine available runtime and give operators a better understanding of when the battery needs to be charged.
The battery management system and industrial battery charger perform different jobs, but the two systems need to work together.
The charger supplies the electrical energy needed to recharge the battery. The BMS monitors battery conditions and helps ensure charging stays within the battery pack's defined operating limits.
Depending on the system architecture, the BMS may communicate information such as voltage, temperature, SOC, allowable charging current, and fault conditions to the charger or equipment controller.
That information can then be used to control the charging process.
The battery, BMS, and charger need to be considered together rather than as completely independent components.
Battery chemistry, pack voltage, capacity, desired charging time, operating environment, and equipment duty cycle can all affect charging requirements.
In industrial equipment, the BMS may need to communicate with more than the battery charger.
Depending on the application, it can exchange information with equipment controllers, PLCs, operator displays, chargers, telematics systems, or diagnostic equipment.
This communication gives the larger system access to information such as SOC, voltage, current, temperature, and fault status.
For engineers designing battery-powered equipment, these requirements should be considered early. The BMS needs to integrate with the machine's electrical and control architecture, not just the battery pack.
There's no single BMS that's appropriate for every industrial battery application.
Selection starts with the battery. The BMS needs to support its chemistry, voltage, cell configuration, expected current, and charging requirements.
The application also matters. Engineers should consider the equipment's operating environment, duty cycle, electrical loads, communication requirements, and expected charging behavior.
For example, equipment operating in a controlled indoor environment may have different requirements than equipment exposed to vibration, moisture, temperature fluctuations, or demanding charge and discharge cycles.
Engineers should also determine what battery information the equipment needs and how that information will be communicated. Testing, diagnostics, fault handling, and service requirements can further influence the BMS design.
The right BMS ultimately depends on both the battery and the application it's powering.
A battery management system provides the monitoring and control needed to understand what's happening within a rechargeable battery. Depending on its design, it can monitor voltage, current, and temperature while supporting battery protection, cell balancing, SOC estimation, SOH monitoring, and communication.
But a BMS doesn't operate by itself.
The battery, BMS, industrial battery charger, electrical load, and equipment controls all interact. A decision made about one component can affect the requirements of another.
Looking at these components as a complete system can help engineers address compatibility and integration requirements earlier in the design process.
Determining the right battery management and charging approach can involve several interconnected design decisions. To determine the right BMS, battery, and charging configuration for your industrial equipment, reach out to our team to discuss your application.