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Battery Fires – a Hot Topic

July 01 2016

Forensic Science Interpreting The Evidence

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Fire Investigation

KBC recently assisted in an arson case in which the Crown offered no evidence after our fire investigation report was served. 

The defendant left the house shortly before lunchtime and returned several hours later to find her house on fire. She was the only key holder, had left the house secure and no signs of forced entry were found.

The Crown’s photographs showed extensive smoke/soot deposits throughout the two-storey property but flame and heat damage were confined almost entirely to a bed in the first floor bedroom. Notably, susceptible plastic items near the bed remained mostly unaffected by heat. This is typical of a slowly developing, smouldering fire.

The defendant explained to the Crown investigator that she had used an electrical heated belt (for back pain) shortly before leaving it on her bed and going out for the day. The Crown investigation included an excavation of the bed to search for electrical wiring associated with a heated belt, but no wiring of apparent significance was found. The Crown’s investigation concluded that, in the absence of any legitimate accidental fire causes, the fire was started deliberately with a naked flame.

In a statement to the Defence, the defendant advised that she had purchased the heated belt online from China or Hong Kong, in 2004 or earlier. She could not recall the manufacturer but stated that the belt was rechargeable. KBC’s search of the internet found a number of online outlets selling heated belts by several different manufacturers.  Some of them are advertised as being lightweight and inconspicuous beneath clothing.  Many are powered by rechargeable lithium-ion batteries, allowing the belts to be used ‘on-the-move’ and without being connected to a mains power supply. 

Having reviewed the available evidence, KBC’s fire investigators concluded that the reported presence of a rechargeable electrical appliance at the area of fire origin should be considered as one possible accidental cause for the fire. Given the nature of the fire and the possible lightweight construction of these heated belts, the belt may have been so severely damaged, with so little of it remaining, that it would be no longer recognisable amongst the debris of the bed from a fingertip search alone. Having read KBC’s report, the Crown concurred and the case was dismissed.

It is important to note that the failure rate of batteries is very low compared to the number of products powered by them. However, they can fail, overheat and cause fires, and they have done so in many cases, leading to documented product recalls on items such as hover boards and laptops. With lithium ion batteries, overcharging, use of the wrong charger, damage to the battery and inherent manufacturing defects can result in a battery overheating, igniting the flammable electrolyte inside the cell and, if amongst combustible materials, causing a fire.

Even the ubiquitous 9V battery that powers many smoke alarms has associated fire hazards, and there are documented examples of fires that have started amongst rubbish containing 9V batteries. The proximity of the positive and negative terminals renders them susceptible to short circuiting if they come into contact with other metal objects during storage or disposal. The heat from this can, and has, caused fires, even in ‘flat’ or ‘weak’ batteries.

This case provides a reminder of the potential hazards of certain batteries and battery-operated devices.  When encountered at fire scenes, it is important that their potential role in a fire is properly considered in conjunction with witness accounts and the type of fire damage observed. Remember, the initial fire investigator may not always be armed with the full facts of a case. If you feel an original fire investigation has not taken specific issues into account, please contact KBC for a full review of the available evidence.


Jennefer Gray
BSc(Hons), MSc, TIFireE, MRSC

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