Vakuum loading on battery packs

Air inclu­sion or air pock­ets in mod­ern Li-bat­tery packs is a seri­ous and dan­ger­ous prob­lem. The isi-sys SE2 sen­sor is able to detect tiny and large defects such as air bub­bles, air pock­ets, cracks and oth­er with­in a sec­ond. The defects can be far below or near to the sur­face. An exam­ple of a bat­tery pack (test sam­ple from Uni­ver­si­ty of Munich, IWB) and the mea­sure­ment result is shown below.

Test set­up:

The test has been done by SE2 sen­sor in com­bi­na­tion with a glass vac­u­um cham­ber for a sim­ple man­u­al test. This is an eco­nom­ic solu­tion for spot NDT by man­u­al ser­vice. For auto­mat­ed series test in pro­duc­tion dif­fer­ent setups are required.

Test poce­dure:

The bat­tery packs are test­ed by small pres­sure dif­fer­ences of some mbar, which can be applied in sec­onds or below in small cham­bers. The sen­sor is mon­i­tor­ing the sur­face of the bat­tery pack while the pres­sure is changed, mea­sur­ing the dif­fer­en­tial defor­ma­tion of the sur­face. Due to the expan­sion of the air bub­bles and air pock­ets, the air inclu­sions can be locat­ed such as shown in the fol­low­ing images.

The first image shows the live view of the bat­tery pack from the sen­sor. The sec­ond shows the recon­truct­ed phase, which is cor­re­spond­ing to the local defor­ma­tion gradient.

battery pack3
















battery pack2

Gen­er­al­ly the required pres­sure dif­fer­ence depends on the defect depth, defect size an the mechan­i­cal stiff­ness of the test­ed struc­ture, but in gen­er­al the load is small due to the high sen­si­tiv­i­ty of the sen­sor detect­ing dif­fer­en­tial defor­ma­tions of the surface.