Analyze the 4 causes of thermal runaway of power battery

Analyze the 4 causes of thermal runaway of power battery

The problem of power battery safety is summarized as "thermal runaway", that is, after reaching a certain temperature, it is uncontrollable, the temperature rises linearly, and then it will burn and explode. Overheating, overcharging, internal short circuit, collision, etc. are some of the key factors that cause thermal runaway of the power battery.

(1) Overheat triggered thermal runaway

The cause of overheating of the power battery comes from the unreasonable selection of the battery and the thermal design, or the external temperature of the battery causes the temperature of the battery to rise and the connector of the cable to loosen. It should be solved from two aspects: battery design and battery management.

Figure 1 Heating Pattern at Different Resistance-shorts

(2) Overcharge triggering thermal runaway

For the reason of this type of overcharging, the solution is first to find the fault of the charger, which can be solved by the full redundancy of the charger; secondly, it is unreasonable to look at the battery management, for example, the voltage of each battery is not monitored.

(3) Internal short circuit triggers thermal runaway

The Boeing 787 had a fire on a battery explosion. When looking for the cause of the accident, it was found that there were metal objects on the electrodes and the battery separator, resulting in an internal short circuit.

To solve the problem of internal short circuit, we must first find the battery manufacturer with good product quality, choose the battery and battery capacity; secondly, predict the safety of the internal short circuit, and find the monomer with internal short circuit before the thermal runaway occurs.

Figure 2 Influence of various short-circuit resistance on thermal runaway of battery

(4) Mechanical trigger thermal runaway

The solution to the collision-triggered thermal runaway is to do a safe design of the battery.

In general, after thermal runaway occurs, it will spread down. For example, after the first section of the thermal runaway, there will be heat transfer, start to spread, and then the whole group will be like firecrackers one by one.

In short, in terms of thermal runaway expansion and suppression, developers must start with two aspects: security protection design and battery management.

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