In really basic terms, a lithium-ion battery is made-up of: (1) lithium-ion cells; (2) a temperature sensor; (3) a voltage converter; (4) a regulator circuit; (5) a notebook connector; (6) a voltage tap; and (7) a battery charge state monitor. The problem occurs in the lithium-ion cell. Among other things, the lithium-ion cell has a metal case that encloses an organic solvent electrolytic solution with a positive electrode and negative electrode separated by a thin plastic separator sheet. When the battery charges, ions of lithium move from the positive electrode to the negative electrode and back again through the separator sheet causing each cell to generate about 3.7 volts. However, if the positive and negative electrodes touch the battery will heat-up and short. The heat causes the cell to expel the electrolytic solution, which will ignite from the heat of the battery.
As with all fire cases, it is important the fire scene is kept preserved and unaltered until such time as all parties are placed on notice and have an opportunity to jointly inspect the scene and retain evidence. These inspections (at the scene and later in the lab) should be done jointly between the injured party, the seller of the product, the manufacturer, and the insurers of each in order to limit spoliation defenses. Prior to destructively examining the battery, it should be scanned by a CT scan. A CT scan makes use of computer-processed combination of many X-ray images taken from different angles to produce cross-sectional (tomographic) images (or virtual “slices”) of specific areas of a scanned object, allowing the user to see inside the object without cutting. The CT scanned images can show the exact failure. Therefore, it is an important step in the forensic investigation, and can be very persuasive evidence in proving a failure mode and resolving a claim.