Lithium-ion batteries have the risk of internal short-circuit due to many factors such as material system and manufacturing process. Although lithium-ion batteries have undergone strict aging and self-discharge screening at the factory, due to process failure and other unpredictable use factors, there is still a certain probability of failure leading to internal short circuits during use. For the power battery, the lithium-ion battery in the battery pack has several hundred or even tens of thousands of knots, which greatly enlarges the probability that the battery pack will be short inside. Due to the great energy contained in the power battery pack, the occurrence of internal short circuit is easy to induce a malignant accident, resulting in casualties and property losses. TE's PPTC and MHP-TA series products offer a possible solution to prevent the occurrence of a malignant accident in the event of an internal short circuit in the power battery.
For a parallel lithium-ion battery module, when one or more of the batteries are short-lived, other batteries in the battery module will discharge them, and the energy of the battery pack will rapidly increase the temperature of the short battery. It is easy to induce thermal runaway, which eventually causes the battery to explode.
As shown in Figure 1
Figure 1: Short indication inside a single cell in the module
Conventional temperature detection can inform the IC to cut off the main circuit when the battery is warming up, but it cannot prevent the continuous discharge inside the parallel battery module, and since the main circuit is cut off, all the energy of the battery module is concentrated in the inner short-circuit battery, but instead increases. The chance of a thermal runaway.
The ideal solution is to cut off the connection circuit between the battery and other batteries in the module when it is found that a certain battery is short and warm. As shown in Figure 2, the TE PPTC or MHP-TA series products are assembled on a single battery. When an internal short circuit occurs, the TE protection device can effectively block the connection between the internal short-circuit battery and other batteries in the module to prevent a serious accident. occur. For a power battery pack with a large number of single cells, the consistency of the internal resistance of the battery and the device is required when the group is assembled, and the MHP-TA has a very good consistency of the device resistance due to its internal bimetal structure, which can greatly satisfy the Battery internal resistance requirements.
The system composition and actual road conditions of lithium-ion power batteries are complex, and the protection of passive devices is indispensable.
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