Embedded Batteries? Have you got a screw loose?

This intriguing battery related story caught my eye recently. An Apple i-phone developed a fault and started emitting black smoke while onboard a commercial  aircraft and had to be doused with a fire extinguisher. The 'fault' turned out to be a rogue screw inside the phone that was left there following a screen repair made by an unauthorised repair centre. The screw was pressed into the soft packaging of the phones embedded Lithium Ion Polymer battery causing a short circuit that resulted in a rapid increase in temperature which quickly led to degradation of the battery itself. Luckily no-one was hurt on this occasion.

This story should act as a warning for original device manufacturers who are designing any sort of electronic device with an embedded battery. You can control your own assembly operations or audit those of your subcontractor - but what happens down the road when someone else opens up your device and and starts messing around with a screwdriver? - how well is the battery protected? Can a foreign body be introduced that could create a short circuit? Furthermore, can you even stop someone from removing the approved battery and replacing it with one they bought for $5 on the internet?

There was a time, in the not so distant past when "no user serviceable parts inside' meant you should leave your screwdriver in the draw - but in the age of the internet it is possible to Google a solution to any repair problem and then watch a HD video where a self appointed 'expert' shows you how to tear down, repair and rebuild almost anything with the use of a pen knife  and a soldering iron. When embedded batteries are concerned this raises serious safety concerns as the OEM cannot control what an end user might attempt to do to the battery, its protection circuitry or the device charge circuitry. The device may just stop working but the illegal repair could start a fire putting both property and lives at risk.

My advice for manufacturers who are designing a device containing an embedded battery is to consider what should happen to the battery when someone opens the device. I would advocate a mechanical disconnect so the battery is rendered useless if the device is opened. In this circumstance the device would have to be returned to an authorized centre for a new battery to be fitted. Manufacturers can further protect themselves by incorporating electronic authentication into their batteries and devices to protect against the use of illegal copies which can damage company reputations and aftermarket sales.

Of course embedded batteries are not the only solution for powering portable electronic devices. Removable battery solutions remain a viable option for all but the smallest of devices. Removable batteries permit the use of multiple batteries per device and do not require the device to be opened when the battery needs replacing. In a product with an extended product life cycle the use of a removable battery makes far more sense as the battery may be replaced many times during the life of the device.

Accutronics CC2300 and CC3800 are good examples of batteries for professional electronic devices where a removable solution is required. They meet all current transportation and IEC safety standards and they have been designed without screws in mind...

Neil