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.