Custom Lithium Ion Battery Pack

A customer's M2AL12-100 batteries burning drum belly analysis

Mar 18, 2019   Pageview:79

First. Overview of the situation

1. Customer feedback M2AL12-100 batteries supplied by Vision Battery has a battery fire accident after one week of replacement operation, requiring on-site analysis and processing.

2. On-site 2 MGE Galaxy 3500 G35T40KH UPS, each equipped with 32 M2AL12-100 batteries (with center line), a total of 64 batteries, the battery is installed in a 4-layer 2-column battery cabinet.

3. One of the UPS is located in the top of the battery cabinet and the battery is on fire. There are 3 batteries in serious combustion, and the remaining batteries are deformed at different degrees.

Second, the battery fire analysis

1. After investigation and analysis of the site situation, the battery fire point is located in the first battery inside the top of the battery cabinet. The reason is that the battery cable is short-circuited with the battery cabinet (the battery cabinet is grounded), and the quality of the non-battery itself. problem. After the fire, the fire department personnel arrived at the scene and also clarified the cause of the fire.

2. The battery connection cable itself should have an insulation function. This time, the short-circuit with the battery cabinet indicates that there is a problem with the insulation function of the cable. There are several possible reasons for this problem:

a. The quality of the cable itself.

b. Physical damage to the cable.

c. High temperature causes cable insulation to fail, and so on.

The battery cable is shorted to the cabinet, and the cable is blown and penetrates the cabinet

The cabinet is broken down

Third, the battery drum belly problem analysis

Before the batch of batteries, they were replaced at the end of 2017 and early 2018 respectively. The drum batteries are 16 batteries of the positive circuit of each UPS, and the negative circuit 16 has no abnormality. The reason for the belly is that under the comprehensive condition of charging the high voltage and the battery operating temperature is high, the internal resistance increases and the drum belly deforms.

1. The UPS charging voltage is too high, and there is a significant difference between positive and negative.

The standard charging voltage of this UPS model is 220V±1% (single: 13.75V), and the positive and negative output has a difference of about 2V. This battery is used in a 25 degree environment, and the upper limit of the floating charging voltage is 13.62V ( See this battery specification), the UPS charging voltage is significantly higher than the battery's upper limit.

PS: In the actual working process, the battery is not bulging due to the low output voltage of the UPS negative circuit.

2. the temperature of the equipment room is too high, the maximum temperature of the battery cabinet exceeds 30 degrees (top of the battery cabinet), and the lowest temperature is about 26 degrees (the bottom of the battery cabinet) is calculated based on the temperature compensation coefficient of the battery. In this environment, the battery float voltage should be 13.5. Around V.

PS: a. the battery positive circuit is located on the top of the battery cabinet and the next layer, the battery negative circuit is located in the bottom layer of the battery cabinet and the upper layer, so that the positive circuit is always running in a higher temperature environment than the negative circuit, which is also the negative circuit is not drum The reason for the belly.

b. The layout is unreasonable. The battery cabinet is too close to the UPS, about 300mm, and the UPS cooling port is facing the top position of the battery cabinet.

c. The battery cabinet is relatively sealed, and the heat dissipation is poor. At the same time, due to the upward characteristics of the heat energy, the temperature at the top of the battery cabinet is higher than the bottom.

d. The position of the battery cabinet is the glass curtain wall.

e. The air conditioning position of the computer room is far away from the battery cabinet, which cannot effectively reduce the operating temperature of the battery.

3. After testing the same batch of batteries in the positive and negative circuits, it is found that the internal resistance of the positive circuit is generally around 9-10 milliohms, and the internal resistance of the negative circuit is generally 4-5 milliohms. The same batch of batteries is used, two circuits are used. The internal resistance and the difference in appearance also confirm the difference between the battery operating at different voltages and different temperatures.

UPS parameters

UPS parameters

UPS parameters

Battery cabinet temperature

UPS and battery cabinet layout

UPS and battery cabinet layout

Comparison of internal resistance of negative positive circuit of the same batch of batteries

Other battery charging voltage in the same room

Fourth, the proposed improvement program

1. The UPS adjusts the charging voltage and ensures the voltage consistency of the positive and negative circuits. The adjustment standard is shown in this battery specification.

2. Adjust the layout of the battery room. The distance between the UPS and the battery cabinet (recommended battery rack) is not less than 800mm, and the UPS heat dissipation port is forbidden to face the battery cabinet.

3. The battery cabinet retains proper maintenance space, and the distance between the two is not less than 600mm.

4. Install battery monitoring to monitor battery voltage, internal resistance, current, temperature and other parameters in real time to ensure safe operation of the battery.

5. Increase the manual inspection work to ensure the safe operation of the power system.