Samsung’s Note 7 battery explosions remains a mystery till date. The company has not bothered to provide any technical explanation of why the explosions happened. In this backdrop, a team named ‘Instrumental’, which helps the hardware companies find and fix the technical issues, took an initiative to follow up the problem, revealing that “the design caused Samsung Galaxy Note 7 battery explosion”.
According to Instrumental, Samsung Galaxy Note 7 smartphone’s battery is a flattened lithium-polymer battery in the form of a “jelly-roll”. It consists of a positive layer made of lithium cobalt oxide, a negative layer made of graphite, and two electrolyte-soaked separator layers made of polymer. The separator layer ensures that the energy flows between the positive and negative, at the same time, prevent those layers from touching each other. In the case of Samsung, this separator layer is thin and the pressure of the battery (due to normal mechanical swell from the battery or when stress comes through back cover, like while sitting with the phone in the back pocket), will squeeze the separator layer to a point where the positive and negative layers touch, leading to explosion.
Also, there was no ceiling above the battery to deal with the natural mechanical swell of the battery. Instrumental also added that the Samsung engineers pushed the boundaries to create a long-lasting battery. “Samsung engineers designed out all of the margins in the thickness of the battery, which is the direction where you get the most capacity gain for each unit of volume,” the team explained.
The engineers have kept the battery inside a CNC-machined pocket to protect it from being poked by other internal components. Hence, they manufactured a super-aggressive battery and protected it internally.
The area where it failed is in the test validation of the battery. Battery tests require an enormous amount of time (perhaps, more than a year), and 1000s of batteries need to tested to get the result. There were reports stating that Samsung chose an internal testing of the batteries and did not depend on the third-party labs. The rush to launch the product in the market and choosing an internal battery test clearly point out to the fact that the manufacturer did not focus properly on the battery testing.
Replacing the battery of Samsung Galaxy Note 7 using a normally designed battery (with standard manufacturing parameters) would have solved the issue. However, choosing this option would have reduced the battery life of Note 7 much below its competitors including iPhone 7 Plus.
In the conclusion of the report, Instrumental stated, “Samsung took a deliberate step towards danger, and their existing test infrastructure and design validation process failed them. They shipped a dangerous product.”