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Problem Description
XX bureau points lithium project feedback SmartLi lithium battery 1pcs lithium temperature equalization alarm ID 0636-001, lithium battery internal cell temperature value there is a large difference.
Alarm phenomenon analysis
(1) As shown in Figure 1 for the lithium cabinet alarm log.
2022-03-18 14:00/22:48:10 battery module equalization alarm, trigger conditions: the same battery module internal, the highest temperature of the cell, and the lowest temperature difference ≥ 20 ℃. This alarm indicates the difference in temperature consistency between the cells at this time, the system does not act and does not affect normal charging and discharging.
2) As shown in Figure 2 for the lithium cabinet operation log.
2022-03-18 14:00 The maximum temperature of battery cabinet 3-module 11 is 48°C and the minimum temperature is 28°C, with a temperature difference of 20°C.
2022-03-18 14:00 The maximum temperature of battery cabinet 3-module 11 is 25 °C, the minimum temperature is 24 °C, and the temperature difference is 1 °C.
It means that the inconsistency of temperature between cells of this battery module has been restored.
(3) As shown in Figure 3 for the monitoring screen photo, the temperature of cell Cell9 and Cell10 is 48℃, and the temperature of adjacent cells Cell7 and Cell8 is 28℃. As heat can be transferred through the battery's shell structural parts, when a cell temperature is high, heat can be transferred to the surrounding cells, which will cause the surrounding cells to rise in temperature. The site only Cell9, Cell10 location of a single sampling point high temperature, the adjacent Cell6 ~ Cell8 location temperature at room temperature, so you can judge the collected Cell9, Cell10 temperature 48 ℃ is not the real temperature.
In summary analysis:
battery cabinet 3-module 11 on March 18 22:00 due to the highest and lowest temperature difference between the internal cells more than 20 ℃, triggering the battery module equalization alarm, the alarm will not cause system action, does not affect the normal charging and discharging. As the temperature of only a single temperature collection point is high at this time, and the temperature of adjacent cells is not significantly higher, we can initially determine that the temperature collection point is not the real high temperature, but the sampling deviation on the temperature collection link, resulting in false alarms.
Solution
For the battery module whose alarm cannot be eliminated, it is recommended to replace the BMU or battery module; for the battery module whose alarm has been eliminated, it is recommended to continue to observe the battery usage status and record the temperature change during the next charge/discharge test.
