Samsung has not yet announced the findings of its internal investigation into the failures of its Galaxy Note 7 (even if it will not be long ), but independent engineers think they have found the reason of the explosions.
According to their results, posted online on their site Instrumental.have , the fire of the battery would not be due to a failure of the lithium-ion battery – the first reason advanced by the south Korean group – but an ” aggressive design “.
In the clear, Samsung would have sought to produce a smartphone as thin as possible, at the risk of compressing the battery, which was too large, ” explains Instrumental.I, which presents itself as a company “helping hardware companies to solve problems related to the design” of their products.
A battery is in need of free space to ” breathe “
the battery of The Note 7 is composed of “a layer of positive-dioxide of cobalt, and lithium”, and ” a layer of negative graphite “, separated by ” two layers of polymer electrolyte “. If these two layers of positive and negative touch each other despite the separation, the energy flowing into the battery ” flows directly into the polymer and the heater “. This can cause an explosion.
How these layers have-they eventually get in touch in the smartphone of Samsung ? As a result of two factors. First of all, because the layers of separation in polymer chosen by Samsung are very fine, and then because the engineers did not have enough free space around the battery so that she has the place to breathe.
In fact, as the electrodes of lithium ions move from the positive pole of the battery to the negative pole – that is to say, when the battery is charging, the battery swells. “The engineer of the battery will tell you, it is necessary to leave a certain percentage of the ceiling around the battery, 10% is a rule of thumb,” write the two authors.
A risk deliberately taken by Samsung, according to the engineers
For their test, engineers have reverse-engineered a Galaxy Note 7 and rendered account of the absence of this free space of 0.5 mm in the battery compartment. This is why the device is susceptible to overheating and at the slightest pressure on the hull, according to the experts.
For Instrumental.’ve, Samsung’s engineers could not ignore such a basic rule and would have deliberately taken the risk of “manufacture super-aggressive” in order to offer a phone thinner and with greater autonomy than its competitors.
” A smaller battery using the manufacturing parameters of the standard would have solved the explosion problem and the problem of swelling “, they stress. But Samsung has been able to solve this solution because it ” would reduce the life span of the battery, placing the Note 7 below the level of its predecessor, the Note 5, as well as that of its biggest competitor, the iPhone 7 Plus “.
If the actual risk of explosion has escaped to Samsung during tests of security, is that ” the battery test takes a lot of time, sometimes a year “, reminds the site. It is possible that the most recent versions of the batteries chosen for the Note 7 has not been tested with the same rigour as the first, argue the researchers.
There remains now a little less than a month for Samsung to formalize itself the reasons of this disaster, which was forced to suspend the production of its new smartphone and to recall 2.5 million copies .
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