Monitoring application of LEM smart battery

With the rapid development of China's communications, power , UPS and other industries, the use of batteries is also increasing rapidly. Under the current conditions of battery use, some unexpected situations often occur, such as a seemingly normal battery failing to discharge electricity during discharge. The main reason for this situation is that the operating status of the battery is not effectively monitored, resulting in one or more batteries in the battery pack failing and not being sorted out in time, which in turn causes the entire battery pack to fail to discharge normally.

As the last safeguard for safe uninterrupted power supply, the battery is also the most unsafe factor in the uninterruptible power supply system. From the system theory, we know that the safety of the system depends on the most unsafe factor in the system, which is the "barrel theory" we often quote.

In terms of the operating mechanism and failure mode of batteries, relevant standards have been issued in China. Necessary devices for battery monitoring, such as voltage inspection meters, are installed in DC power supply situations. However, depending on the working conditions of the backup battery, it is possible that it will not be discharged for a long time and may fail during two regular verification discharge tests, while the terminal voltage of the battery is completely normal. As shown in the following figure (IEEE):

It can be seen from this that detecting voltage alone is not enough, and it is easy to mislead users and use bad batteries as good batteries, which is quite harmful. So, in addition to monitoring voltage, is there any good way to more effectively monitor the status of the battery, and give a warning signal when the battery performance drops to a certain level, so that we can replace the battery or perform special maintenance before the battery fails, thereby avoiding catastrophic power outages. The answer is of course yes. By measuring the state of the battery's internal resistance , the degree of battery degradation can be effectively predicted, that is, the battery's health status SOH (Status Of Health) can be accurately monitored. As shown below:

The yellow trend line shows that the internal resistance of the battery increases sharply from October to November due to various reasons. Therefore, it can be judged that the state of the battery has seriously deteriorated. After discharging the battery, it is confirmed that the battery has indeed failed.

[page] LEM has developed the world's smallest and most highly functional intelligent battery sensor Sentinel based on the operating mechanism and failure mode of batteries. It can accurately measure the internal resistance, temperature and voltage of single batteries .

The device has the following main features: 1. Measuring voltage 1.5V-15V, accuracy +/- 0.5%

2. Temperature error, +/- 2℃

3. The measurement repeatability of internal resistance is +/- 2%

4. All connectors are used, which makes installation very quick

5. <3mA in power saving mode

6. 5-year quality assurance

With the complete solution provided by LEM, users can build a perfect battery monitoring system in a very short time.