- 外短路：external short circuit
- 内短路 internal short circuit
- 过充电 Overcharge
- 强制放电forced discharge
- 电气安全 Electrical Safety
The cell will leak if the design and producing process is not good and the cell will be affected by the condition as T1-T4 in UN38.3.We must be sure the cell will not leak during the transport through test .And the package instruct guarantees the transport will be safe even if the cell leaks
External short circuit will cause danger . The temperature of lithium batteries rises higher if happened ,and in certain condition battery will fire and explode.T5 in UN38.3 simulates external short circuit ,This test requires lithium battery is safe after it is subject to the special condition as T1-T4 in UN38.3. The package instruct also requires the protection for external short circuit .
The reasons to make the battery internal short circuit are (1)the separator is defective (2)little part of metal enters the cell during producing (3)Lithium metal comes into being because the battery is often overcharged . Internal short circuit is the main reason for fire and explosion by lithium battery .We should improvedesign to make the battery safe through test.
UN38.3 中T6 碰撞实验是模拟电池内短路的。当然现有的T6 碰撞不能很真实的模拟电池内短路情况，许多机构和专家正在研究更合适的实验方法，但在最近的UN38.3 草案中增加了挤压实验，而且大部分锂电池都要求用挤压实验，目前的挤压实验不能使很多电池形成内短路，对安全运输很不利，我们也提出自己意见，递交了正式文件
T6 in UN38.3 simulates the internal short circuit, As you know , It is incomplete same as the reality . Many experts in different institute are developing a good test method . In recent draft UN38.3 ,Crush test is used for most kinds of lithium cells. The crush test with 3000N can’t make most kinds of cells internal short circuit .It is not benefit for safe transport . We have submitted a formal document to express our opinion .
It is not fit for lithium metal battery. Most of them are primary.
Due to failure of the voltage limited circuit or deviation of the value of limited voltage , Lithium ion battery is often overcharged . Lithium metal comes into being ,Unstable substance is produced, the electrolyte is decomposed , Which will cause fire ,explosion and extreme temperature .Therefore lithium ion battery needs the protection for overcharge .
T7 in UN38.3 verifies the function of overcharge protection and the safety of the battery under overcharge . This danger mainly exists in the used batteries
lithium metal cell will produce explosive substance when it is over-discharged . The explosive substance will explode under certain condition. Which should be protected .
The copper will be separated out on the positive polar if the lithium ion cell is over-discharged . It has an effect on performance .
T8 in UN38.3 verifies the cell is safe under over-discharge condition.
This is for larger lithium battery . Larger lithium battery is composed of a lot of small cells in parallel and in series.
Only terminal voltage of battery is controlled during charging .The cell blocks in serial must have a same voltage . If not ,some cell blocks must be overcharged , Overcharge will cause danger. So the cell consistency is very important.
Many cells are in parallel . If the voltage of one cell drops down due to internal short circuit or other reasons. The larger current will exist in this cell block . Which will make the cell fire or explode . We should pay more attention to this kind of danger .Developing a good test to avoid it .
Additional , larger lithium battery has high voltage ,High voltage will bring electrical danger . The test of High POT and insulated impedance is also needed .
There is Battery management system (BMS) in the larger battery . BMS is powered by cell module ,If the short circuit happens on the circuit board , The larger current will flow the printed circuit board because the cell module has a large power . It is also possible for this current to make the printed circuit board fire . We should do some tests to avoid fire. (We often find the screw in the larger battery dropped out , It is possible for the screw to make the printed circuit board short circuit .)