Today’s electronic devices, as small as TWS headphones and wearable devices, as large as electric cars, are inseparable from the lithium-ion or polymer battery power supply. Depending on the amount of power required by the electronic device, the battery pack may consist of a plurality of battery cells arranged. The charge and discharge of the battery pack, input/output voltage, and current status need to be monitored and measured precisely to ensure the safe power supply of electronic equipment. This requires a special battery management system (BMS) to monitor the operating state of the battery pack, which is used for battery pack monitoring, calculation, communication, and protection. The BMS is an important part of maintaining the normal operation of the battery system, with special attention to balancing the battery BMS voltage to ensure the stability and life of the battery pack.
The voltage of the BMS ranges from tens of volts to hundreds of volts. The higher the voltage, the greater the power. The voltage requirements of the BMS in different applications are different. Through this article, let’s explore the voltage categories of the BMS and the corresponding applications in different ranges. As well as the BMS how to monitor the voltage of each cell or module in the battery pack in real-time, how the BMS detects voltage anomalies, and how to maintain the voltage balance of the battery pack.
Different Categories of BMS Voltage
Classification According to Different Types of Voltage
Different types of voltages in battery management systems are suitable for different situations. Here are some examples:
Input voltage: The input voltage is usually used in the charging process and is widely used in electric vehicle charging stations and home solar power generation systems. Charging stations need to ensure the stability of the 2s BMS input voltage to improve the charging speed and efficiency. Solar power systems need to convert the DC voltage generated by solar panels into AC voltage suitable for home electricity. The input voltage is usually a low DC voltage (such as 12V or 24V) to match the output voltage of the solar panel. The output voltage needs to be converted to the standard AC voltage for household electricity (e.g. 220V or 110V).
Output voltage: The output voltage is suitable for power supply processes, such as industrial equipment, home appliances, etc. In industrial energy storage systems, the BMS output voltage usually needs to match the voltage demand of industrial equipment to convert the stored energy into usable AC electrical energy, which may operate in a high BMS voltage range (e.g. 800V to 1500V) to meet the energy demand of industrial production.
Unit voltage: Unit voltage refers to the voltage of each cell in the battery pack. In electric vehicles and energy storage systems, the BMS needs to monitor and balance the voltage of each cell to ensure the performance and lifetime of the entire battery pack. In electric vehicles, the cell voltage is usually in the range of 200V to 400V to meet the high power demand of electric vehicles while balancing the performance of each battery cell. The overall voltage may be in the range of 300V to 800V to meet the working requirements of electric vehicles.
Classification According to Different Ranges of Voltage
When it comes to different ranges of low, medium, and high voltages, the actual values may vary depending on different applications, technologies, and developments. Here are some examples of approximate voltage ranges in common applications:
Low voltage range: The input voltage of the low voltage range is generally between 1V and 12V, which is suitable for mobile devices, sensors, handheld tools, and other small devices. These applications usually require a certain volume and weight of the battery and need to operate in a BMS low voltage range, while requiring a long service life. The output voltage is usually between 5V and 24V, which is common in application scenarios such as USB chargers or home electronic devices.
Medium voltage range: Medium voltage range of single voltage is usually between 12V and 48V, suitable for small and medium-sized power tools, light electric vehicles, and other applications. These applications have certain requirements on the performance and life of the battery and require a balanced voltage in the medium voltage range. The output voltage is usually between 24V and 100V, which is suitable for some household appliances, light industrial equipment, etc.
High voltage range: The single voltage in the high voltage BMS range is generally between 48V and 800V, which is suitable for high-power applications such as electric vehicles, industrial equipment, and large-scale energy storage systems. These applications have high requirements on the output power and energy density of the battery and require high performance over a high voltage battery BMS range. The output voltage is usually above 100V, which is used in industrial equipment, large energy storage systems, high-power solar inverters, etc.
How to Detect Voltage Anomaly
At present, in the battery management system, a series of sensors, circuits, and algorithms are used to monitor the battery cell voltage sum detection, pack point voltage detection, and insulation point voltage detection in real time to judge whether the battery voltage is normal. Specifically, the battery cell voltage sum pack point voltage is compared. If the two are the same, the battery voltage state is normal. If the two voltages are not the same, it indicates that the voltage state of the battery is abnormal, and the battery has a fault. This method can detect whether the battery voltage is normal, but when the voltage state is abnormal, it is often difficult to quickly determine which detection point is faulty.
In this regard, MOKOEnergy provides a battery voltage abnormal state detection method in the battery management system and its detection system and battery management system. The battery voltage abnormal detection point state detection method in the battery management system includes the following steps: based on the BMS circuit, establish the equivalent conversion relationship between the battery voltage value and the voltage value of multiple detection points; Real-time detection of battery voltage value and multiple detection points voltage value; The voltage value of the battery obtained in real-time and the voltage value of multiple detection points were converted and compared. If the voltage value of the battery and the voltage value of multiple detection points are equal after equal conversion, the system is judged to be normal; If there is a non-equivalent value between the battery voltage value and the voltage value of multiple detection points after equal conversion, the voltage detection point corresponding to the non-equivalent value is abnormal. The innovative battery voltage state detection method in the BMS system provided by MOKOEnergy can not only conveniently monitor whether there is abnormal battery voltage, but also quickly locate the abnormal location, which has strong practicability and convenience.
How to Keep the Voltage Balance of the Battery Pack
The BMS maintains the voltage balance of the battery pack through voltage balancing operation, thus improving the performance, lifetime, and safety of the battery pack. Here are the general steps of how a BMS can achieve voltage balance in a battery pack:
- Detection of imbalance: The BMS continuously monitors the voltage of each cell or module in the battery pack. When the voltage of some cells is significantly higher than that of others, or the voltage difference exceeds a preset threshold, the BMS determines that the battery pack is unbalanced.
- Decision balancing strategy: According to the preset balancing strategy, BMS will decide when to perform voltage balancing operations. The equalization strategy may be based on factors such as time, voltage difference, capacity difference, etc.
- Balancing operation: After deciding to balance the voltage, BMS will discharge the battery cell with a higher voltage or charge the cell with a lower voltage through the charge and discharge controller. This helps reduce voltage differences between battery cells.
- Monitoring and adjustment: During the voltage balancing operation, BMS will continuously monitor the voltage changes of battery cells to ensure that the voltage difference is gradually reduced during the balancing process.
- Control strategy: BMS will adjust the parameters of the balancing operation according to the actual situation, such as the size, direction, and time of BMS charging voltage and discharging current, to ensure the best effect of voltage balancing operation.
- Equalization cycle: The equalization operation can be carried out periodically or triggered when the BMS battery pack current reaches the imbalance threshold. The choice of equalization period depends on the battery type, application requirements, and BMS design.
To sum up, BMS voltage management plays an important role in the battery system, it not only protects the performance and life of the battery pack but to achieve safe and stable operation of the key link. Through precise monitoring and control technology, BMS can maintain the voltage balance within the battery pack to prevent problems such as overcharge or over-discharge.
In the battery voltage balance, MOKOEnergy has rich experience and advanced technology, can effectively achieve the internal battery voltage balance, but also put forward a practical and quick way to detect specific voltage anomalies, to ensure the safety and stability of the system operation. Whether in the field of electric vehicles or energy storage systems, MOKOEnergy’s BMS can play an excellent performance, to provide users with reliable battery voltage management services. Click here for a free consultation.
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