Abstract: The safety of lithium-ion traction batteries is a key point during the development of electric vehicles.
Some safety abuse tests, such as the penetration test, the crush test and the heat test, were done to investigate
the safety characteristic change in different cycles for a lithium iron phosphate power battery. The relationship
between the thermal abuse behavior parameters and the battery cycle life was analyzed before and after
100~500 cycles. The results show that according to the starting point of self-heating, fresh batteries have not
the highest thermal activities; battery thermal activities firstly increase, then decrease along with the cycle time
increasing . This phenomenon can be attributed to that the active materials in battery activate gradually to
achieve the best performance, afterwards decrease with increasing cycles.

Key words: electrical vehicles, power batteries, safety, normal cycle, thermal behavior