Short circuit protection solution for 18650 li ion rechargeable battery

　　Short circuit protection solution for 18650 li ion rechargeable battery. Lithium batteries have the risk of short circuit, and for 18650 li ion rechargeable batterys, the number of hundreds or even tens of thousands of lithium-ion batteries greatly increases the probability of short circuit. Short circuit of lithium battery pack is an inevitable thing in the battery production process. Once the power battery has an internal short circuit, a vicious accident will occur. Therefore, every battery factory should understand new methods to prevent short circuit of lithium battery pack.

　　Short circuit protection solution for 18650 li ion rechargeable battery

　　For parallel-connected lithium-ion power battery modules, when one or several batteries have an internal short-circuit, the other batteries in the battery module will discharge it, and the energy of the battery pack will cause the temperature of the internal-short-lived battery to rise rapidly. It is easy to induce thermal runaway, eventually causing the lithium battery pack to catch fire and explode.

　　Everyone must be familiar with the lithium battery protection board. Everyone knows its function, which is to protect the lithium battery pack or single-cell lithium battery from overcharge, overdischarge and short circuit.

　　When it is found that a certain battery is short-circuited and heats up, the connection circuit between the battery and other batteries in the module can be cut off. Assemble TEPPTC or MHP-TA series products 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 the occurrence of serious accidents.

　　For 18650 li ion rechargeable batterys with a large number of single cells, the consistency of the internal resistance of the batteries and devices is required to be high during assembly. However, due to its internal bimetallic structure, MHP-TA has very good consistency of device resistance, which can greatly meet the requirements. Requirements for battery internal resistance. The system composition of power lithium batteries and the actual road conditions are complex, so the protection of passive components is essential.

　　During application, in order to prevent the short-circuit protection circuit from malfunctioning due to transient overload, the short-circuit protection circuit has a certain delay. And due to the error of the current detection resistor, the delay of the current detection signal and the system response, usually, the short-circuit protection time is set from 200μS to 1000μS according to different applications, which requires the power MOSFET to be able to operate during this time under high short-circuit current. Internal security work also increases the difficulty of system design.

　　The high-security 18650 li ion rechargeable battery discharge short-circuit protection control system uses a high-power positive temperature coefficient thermistor in series with the discharge overcurrent protection field effect transistor loop to limit the short-circuit discharge instantaneous current of the 18650 li ion rechargeable battery within a certain range; load The short-circuit sampling detection point voltage is greater than 0.7V, which wakes up the fast short-circuit detection and control circuit and promptly turns off the discharge overcurrent protection field effect transistor;

　　When the discharge load is short-circuited, once the discharge overcurrent protection field effect transistor or the fast short circuit detection and control circuit fails and fails to turn off the field effect transistor in time, the high-power positive temperature coefficient thermistor will also become high resistance within 0.5s. State-blocking the short-circuit current and limiting the short-circuit current to the mA level will improve the safety and reliability of the system tens of thousands of times;

　　The quiescent current of the fast short-circuit current detection and control circuit is <2μA to protect the discharge over-current protection field effect transistor from over-current breakdown, thereby effectively improving the reliability of the discharge short-circuit protection of the 18650 li ion rechargeable battery.

　　Summary: Therefore, it is very important and necessary to do a good job in short-circuit protection of 18650 li ion rechargeable batterys, and learning new methods of holding and preventing short-circuit of lithium-ion battery packs is one of the standards that every battery person should achieve.

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