Internal short circuit protection of lithium ion battery
Due to the influence of many factors such as material system and manufacturing process, lithium-ion battery has the risk of internal short circuit.
Although lithium-ion batteries have undergone strict aging and self discharge screening when leaving the factory, due to process failure and other unpredictable use factors, there is still a certain failure probability, resulting in internal short circuit during use.
For power batteries, there are hundreds or even tens of thousands of lithium-ion batteries in the battery pack, which greatly enlarges the probability of short-circuit in the battery pack.
Due to the great energy contained in the power battery pack, the occurrence of internal short circuit is very easy to induce malignant accidents, resulting in casualties and property losses.
For parallel lithium-ion power battery modules, when one or several batteries are short-term, other batteries in the battery module will discharge them, and the energy of the battery pack will rapidly increase the temperature of the short-term battery, which is very easy to induce heating out of control, and finally lead to battery fire and explosion. As shown in the diagram:
Although the conventional temperature detection can tell the IC to cut off the main circuit when the battery heats up, it can not prevent the continuous discharge inside the parallel battery module. Moreover, due to the cut-off of the main circuit, all the energy of the battery module is concentrated in the internal short circuit battery, which increases the probability of 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 battery has internal short and temperature rise.
As shown in the figure, te PPTC or mhp-ta series products are assembled on a single battery. When an internal short circuit occurs, te protection device can effectively block the connection between the internal short circuit battery and other batteries in the module to prevent malignant accidents.
For the power battery pack with a large number of single batteries, the consistency of the internal resistance of the battery and devices is high. Due to its internal bimetallic structure, the consistency of the device resistance of mhp-ta is very good, which can greatly meet the requirements of the internal resistance of the battery.
The system composition and actual road conditions of lithium-ion power battery are complex, and the protection of passive devices is essential.