In October, a New York City Police Department officer on Staten Island wore a body camera that unexpectedly began smoking and caught on fire. Thankfully, the officer was unharmed, but it did cause the NYPD to stop all usage of that particular body camera – the VIEVU LE5 Body-Worn Camera – until the incident was investigated and the cause determined by a forensic expert. This unfortunately impedes the department’s goal of having every officer outfitted with a body camera by 2019.
As a battery expert, I’ve been asked to comment on this incident, the shorting of the battery in the body camera. First, it was surprising to hear that a thermal event took place as described since the body camera is powered by a Lithium-ion battery and it is unusual for this type of battery to fail in this way. It’s a more common occurrence in devices that contain Lithium Polymer batteries.
A body camera of this type does not have a removeable or rechargeable battery like those that GTS manufactures. Rather, it’s a battery similar to those in a smartphone. The Lithium-ion battery is embedded in the device so a drop or contact could trigger the battery to short circuit and even erupt.
But the forensic investigation has revealed that the Lithium-ion battery failure was likely caused by a paper clip routinely used to reset the device. According the report, the investigator found no indication the explosion of a Vievu LE-5 camera was caused by a failure of the camera circuit board, or the wiring. In addition, it did not appear that the camera had been damaged prior to catching fire. The forensic investigator noted that the likely cause was that a reset switch on the bottom of the camera became dislodged when the officer used a paper clip — an approved method — to reset the device.
According to a New York news outlet, NYPD deputy commissioner for technology, Jessica Tisch, described the possible scenarios in a briefing: first, the reset switch may have dislodged and scraped battery; second, the paper clip may have “directly accessed” the battery.
No matter the exact cause, it’s clear that a battery failure of this type jeopardizes the personal safety of officers and others who wear devices like this one. This demands that future designs should prevent internal access by users to the battery; that is, to the cells or circuitry. Device designers and those who consult on the design and implementation of batteries should ensure there is sufficient shielding or masking – for example, insulators, rubber plugs or discs – to prevent foreign objects such as conductive metal to penetrate or otherwise touch any of the internal battery components.
The circuitry and battery should be designed to prevent any metal object from touching and possible shorting PCB traces, safety components, the cell, and intercell straps. This would keep all foreign materials and users from accessing routinely, or inadvertently, internal battery components that may compromise safety of the system.
The event experienced by the NYPD could have been avoided with a proper battery and system design that does not permit outside objects to make contact with the cell, PCB or other internal components. Battery safety for wearable devices really boils down to proper design and construction of battery packs for industrial, enterprise and public safety users.