The Importance of State of Charge (SOC) and State of Health (SOH) in Battery Management Systems

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The State of Charge (SOC) and the State of Health (SOH) are two critical factors in the world of rechargeable batteries that are extremely important in determining the performance and longevity of the battery. The Battery Management System (BMS), which monitors and controls these parameters, provides crucial knowledge about the capacity and state of the battery. In this article, we examine the role that SOC and SOH play in battery management systems and how they effectively operate batteries.

Understanding State of Charge (SOC)

The State of Charge calculates the battery's current capacity as a proportion of its maximum capacity. It can be compared to your car's fuel gauge in simpler words. It informs you of the battery's remaining capacity and when it would need to be recharged.

Whether it's an electric vehicle, a smartphone, or a home energy storage system, the SOC is a crucial characteristic for any battery-powered system. The user may properly control their energy usage and make plans for recharging by knowing the SOC.

Even when the battery is not being utilized, it rapidly loses SOC over time. It's known as self-discharge.

Understanding State of Health (SOH)

The State of Health provides information on the battery's general health while the SOC indicates how much charge is still in the battery. It represents a comparison between the battery's present capacity and its initial capacity at purchase.

The SOH offers useful details regarding the battery's life expectancy and potential replacement dates. Low SOH batteries are less able to store electronic charges at a given voltage, which reduces their availability.

A common illustration of the impact of SOC and SOH for a battery is shown in the diagram below:

Figure 1: SOC and SOH effects of a battery

SOC increases with higher battery voltage and it declines as the battery drains. The SOH, or more simply put, the battery life, decreases as the number of charge and discharge cycles rises.

The Role of the Battery Management System (BMS)

The SOC and SOH of the battery are being managed by the battery management system. The BMS can assure the battery's safe and effective operation, increase its longevity, and avert any issues by continuously monitoring these parameters.

Monitoring SOC And SOH

This entails measuring the battery's voltage, current, and temperature and using the results to determine the SOC and SOH.

The SOC is normally calculated by the BMS using the voltage and current that are flowing into and out of the battery. The SOH, on the other hand, is often established based on elements like the quantity of charge/discharge cycles the battery has seen, its age, and its history of temperature.

Ensuring Safe Operation

The BMS can make sure the battery is operating safely by keeping an eye on the SOC and SOH. For instance, if the SOC is too high or too low, it can cause overcharging or deep discharging, which both have the potential to harm the battery and cause safety problems like chemical leaks or fire. The BMS can avoid these issues and guarantee the battery's safe functioning by maintaining the SOC within a safe range. The BMS can inform the user that the battery might need to be changed soon if the SOH is low.

Maximizing Battery Lifespan

Additionally essential to increasing battery life are the SOC and SOH. The BMS can optimize charging and discharging to lengthen battery life by keeping the SOC within a predetermined range and monitoring the SOH.

Optimizing Energy Usage

Optimizing energy use also involves being aware of the SOH and SOC. For instance, knowing the SOC in an electric car might assist the driver in planning their route and charging stations. Similar to this, understanding the SOC and SOH in a home energy storage system can help optimize energy use and lower electricity bills.

Conclusion

State of Charge (SOC) and State of Health (SOH) are crucial factors in the management of rechargeable batteries. The Battery Management System (BMS) ensures the safe, effective, and ideal operation of batteries by monitoring and controlling these parameters. Understanding the significance of SOC and SOH is essential in the field of battery management, regardless of whether you work for a company that produces battery-powered equipment, develops BMS systems, or are just an admirer of battery technology.