Lithium-ion batteries are susceptible to internal short circuits due to various factors, including their material composition and manufacturing process. Although lithium-ion batteries undergo rigorous aging and self-discharge screening at the factory, process failures and other unpredictable usage factors still present a certain probability of failure, leading to internal short circuits during use. Power lithium-ion battery packs often contain hundreds or even tens of thousands of cells, significantly increasing the probability of internal short circuits. Because power lithium-ion battery packs contain extremely high levels of energy, internal short circuits can easily trigger catastrophic accidents, resulting in personal injury and property damage.
TE's PPTC and MHP-TA series products offer a possible solution to prevent catastrophic accidents in the event of an internal short circuit in a power lithium-ion battery. In parallel lithium-ion power battery modules, when one or more cells experience an internal short circuit, the other cells in the module will discharge, causing the battery pack's energy to rapidly increase the temperature of the internally shorted cell. This can easily induce thermal runaway, ultimately leading to a battery fire and explosion, as shown in Figure 1.
While conventional temperature detection can alert the IC to cut off the main circuit when the battery heats up, it cannot prevent continued discharge within the parallel battery module. Furthermore, because the main circuit is cut off, all the energy in the battery module is concentrated in the internally short-circuited battery, which actually increases the probability of thermal runaway. The ideal solution is to disconnect the connection circuit between that battery and the other batteries in the module when an internal short circuit is detected and the battery heats up.
As shown in Figure 2, TEPPTC or MHP-TA series products are assembled on a single battery cell. When an internal short circuit occurs, the TE protection device can effectively block the connection between the internally short-circuited battery and other batteries in the module, preventing catastrophic accidents. For power lithium-ion battery packs with a large number of individual cells, the consistency of battery and device internal resistance is crucial during assembly. Due to its internal bimetallic structure, MHP-TA exhibits excellent device resistance consistency, which can greatly satisfy the requirements for battery internal resistance.
The dangers of short circuits in lithium-ion power lithium-ion batteries are extremely great, so it is essential to protect the battery pack from short circuits. The two methods mentioned above can effectively protect the circuit when a short circuit occurs in the battery.
