Dumb Nails

Dumb Nails

The nail test for lithium-ion batteries is now the "smart nail" test as researchers at Dalhousie University have developed a nail with a heat sensing tip.

The project, as detailed in the Journal of Power Sources, lists these highlights:

  • A “smart” nail with a thermocouple in the tip is described.
  • Accurate temperature/time curves can be obtained at the site of nail penetration.
  • Easily measure differences in response of Li-ion cells to speed/depth of penetration.
The abstract attached to the article states the following:

"Nail penetration is one safety test that Li-ion cells experience in order to simulate some aspects of an internal short circuit event. To our knowledge, nail penetration is usually performed with an ordinary steel nail. Normally, the only data gathered has been a simple pass/fail result depending on whether or not the cell emitted smoke or flame, along with a thermocouple on the surface of the cell. A “smart nail” has been developed to allow the collection of temperature versus time data at the point of nail penetration. This nail, in conjunction with a thermocouple on the cell surface and tabs on the ends to measure voltage, should provide some new insights into the behavior of cells during this type of abuse testing as well as aid in the developing of safer Li-ion cell chemistries."

The "smart nail" makes sense to us as it seems one would want to know the temperatures within a punctured battery over time.  This, in a way, can gauge thermal runaway in different battery chemistries and in different pack constructions.

Source: Science Direct