Shock Test

The shock test is to represent the sudden decceleration of an object such as when it is dropped and hits the floor or it is involved in a crash. It can also be invoked in normal transport such as when a plan experiences turbulence or a vehicle is driven over a speed bump.

table for UN38.3 T4 shock test

In the process of updating UN38.3 transport testing requirements the sub-committee of experts [1] explain the physics behind the equations used in UN38.3 T4

COHSTA presentation showing deformation of larger battery packs on impact

COSHTA [2] explain this in their presentation:

  • So we have established two things:
    • Larger battery assemblies experience lower accelerations than smaller batteries during shock events in transportation due to the deformations in the system under load.
      • Therefore the constant acceleration test exposes larger batteries to disproportionally larger forces than they would experience in reality.
    • Battery Assemblies of higher mass experience forces in transportation that are not proportionally higher than batteries of smaller mass.
      • Therefore reduction in force from the constant acceleration line of T4 is warranted.
  • And the corollary of this is that the surface that an item is attached to for transport can only impart a maximum force on that item before it deforms under load.
    • An airplane floor, for instance, will deform significantly under the force that is necessary to accelerate a large battery assembly, thereby reducing the acceleration and the magnitude of the force.

References

  1. Report on the third meeting of the informal working group on testing large lithium batteries, Sub-Committee of Experts on the Transport of Dangerous Goods, UN/SCETDG/46/INF.11, October 2014
  2. Considerations About UN38.3 T4 Test, and its Applicability to Large Lithium Batteries, COSHTA