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Lithium Ion Batteries: Cause or Victim?

Blaze Fire Investigation is now know as Anderson Engineering. (updated 6/28/17)

Lithium Ion batteries are ubiquitous in today's electronic environment. Everything from cell phones to hover-boards to electric vehicles run on Lithium Ion batteries. This type of battery is attractive to manufacturers because of its relatively high specific energy. This means there is more energy per unit of mass in a Lithium Ion battery than there is in other types of batteries. The high specific energy is great for packing a lot of power into a small package. But upon failure, that same energy can be released in a dangerous fashion. 

In that way, the Lithium Ion battery is not unlike other electrical failures. We know that electrical failure in an appliance or circuit can cause a fire. We also know that in a fire environment, the breakdown of insulation systems can cause an electrical failure on a circuit or appliance. During a fire investigation, an investigation team has to determine if the evidence of failure noted after the fire was a cause of the fire or a victim of the fire. 

Similarly, a Lithium Ion battery can fail and cause a fire or it can fail due to being attacked by a fire. 

There have been well documented failure modes of Lithium Ion batteries that result in a thermal run-away condition. The thermal run-away condition can result in a pressure build-up internal to the battery cell that is relieved by a venting with flame. The heat generated in the battery cell can ignite near-by combustible materials such as a plastic housing. Even more dangerous is the possibility of the battery cell contents being expelled under pressure causing the flaming battery to rocket across a room and ignite combustible materials. 

However, when a Lithium Ion battery is subjected to fire temperature, these same failures can occur. The fire temperatures induce a short in the battery and the energy that remains in the battery is dissipated, sometimes with spectacular results. The shorting of the battery cell due to being attacked by a fire can cause the cell to expand, can cause the cell to vent with flame, and can cause the cell contents to be expelled. 

After a fire it is difficult to tell if the damage to the Lithium Ion batteries indicates that they caused the fire or were a victim of the fire. The investigation team must apply the same type of methodology to the Lithium Ion battery evidence as it does to evidence of more traditional electrical failures. In order to determine if the batteries caused the fire, other questions must be answered.

  •  Is there physical evidence that the batteries failed? 
  • Were the batteries located at the point of fire origin? 
  • Can all other possible causes of the fire be eliminated? 

 

If the investigation team can answer yes to these three questions, they are well on the way to an opinion that the Lithium Ion batteries failed and caused the fire. 

Lithium ion battery pack that was fully discharged when it burned.
Lithium Ion battery pack that was fully discharged and burned in a fire. Note that the cells remained largely intact and did not expand. This is due to the relatively low energy remaining in the cells at the time of the fire.

 

Lithium ion battery pack that was fully discharged when it burned. An expelled lithium ion battery cell that was fully charged when it burned..
Lithium Ion battery pack that was fully discharged and burned in a fire. Note that the cells remained largely intact and did not expand. This is due to the relatively low energy remaining in the cells at the time of the fire.
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