Samsung Galaxy Note 7: The Unfolding Battery Crisis Timeline

A lithium-ion battery is a sandwich of a positive electrode, a negative electrode and a thin plastic separator, rolled or stacked inside a pouch and soaked in a flammable electrolyte. The separator keeps the electrodes apart while letting lithium ions pass. If anything breaks through it, the electrodes touch, current flows inside the cell and it heats up rapidly. Above a certain temperature the materials start to break down and release more heat and gas, a chain reaction known as thermal runaway.

Samsung’s investigation found two different routes to the same short circuit. In Battery A, used in most original phones, the corner of the pouch did not leave enough room for the electrodes, so the negative electrode was bent and, over time, could meet the positive electrode. In Battery B, used in the replacements, welding at the positive tab left burrs high enough to push through the separator, and some cells were missing the insulation tape meant to protect that spot. Samsung, UL, Exponent and TÜV Rheinland each found no fault in the phone’s own hardware or software.

The design made both failures more likely. Samsung had fitted its biggest Note battery yet into a thin body with tight tolerances, leaving little room for normal swelling or for manufacturing variation. That is why one of the multi-layer measures Samsung announced afterwards was simply more space around the battery.

Samsung acted quickly. Within two weeks of the first public reports it had stopped sales and promised to replace every phone, at a time when it believed it understood the problem: a defect in one supplier’s batteries. Replacements would use cells from the other supplier. But that supplier had to increase production sharply to cover millions of phones, and its cells had a different, unrelated flaw. The replacements went out before anyone had shown that they could not fail in some other way.

The programme also started outside the formal recall process. Samsung announced its exchange on 2 September, but the US recall, which made sales illegal and set out the remedy, did not come until 15 September. In the meantime, consumers heard mixed messages about whether their phones were safe. When the replacements began to fail in early October, the company had already used up much of the trust the quick response had earned.

The point of the check was to test batteries at several stages, from cell production to the finished phone, rather than relying on a single inspection. X-ray and disassembly tests target exactly the kinds of hidden defects that caused the Note7 fires. Samsung’s multi-layer measures also covered phone design: more space around the battery, brackets to protect it from impact, and charging software that limits temperature, current and charging time.

Samsung put the cost at about $5.3 billion in lost operating profit over three quarters, for refunds, replacements, logistics, write-offs and lost sales. It was large, but Samsung’s memory chip business was booming and the company reported strong profits again within months. The Galaxy S8, launched in April 2017, and the Note8 in August sold well.

The harder damage was to trust. Airline announcements naming the Note7 were repeated at gates around the world for months, a constant reminder of the failure. Samsung responded by making battery safety part of its marketing and, for years, by keeping battery sizes and charging speeds conservative. Carriers and retailers, who had handled millions of returns, also became more demanding about the testing they expect before a launch.

Ten years after the Note7’s launch, the risks it exposed have not gone away; they have moved. Phones are now among the safer lithium-ion products, with better testing and more conservative designs. The bigger concerns are cheap power banks, vapes and e-bikes, which are made by thousands of suppliers with uneven quality control and carried everywhere, including on planes.

Regulators have responded. The FAA verified 93 lithium battery incidents on aircraft in 2025. Since 27 March 2026, ICAO rules limit international passengers to two power banks and ban charging them on board, after a series of cabin fires including the Air Busan fire in January 2025. In Europe, the Batteries Regulation will require portable batteries in new devices to be replaceable by users from 18 February 2027, although phones meeting separate durability standards can be exempted.

The Galaxy Note7 went from launch to withdrawal in less than ten weeks. What began as a few photos of burnt phones in South Korea became two recalls, a worldwide flight ban and a $5.3 billion loss, because a fix was shipped before it was proven. Samsung’s January 2017 investigation found that two suppliers’ batteries had failed for different reasons inside a design with little margin for error.

The lasting lesson is that battery safety depends on the whole system, from cell design and supplier quality to independent testing and clear recalls. A decade later, as power banks and vapes cause more fires on planes than phones do, regulators are applying the same lesson to products far cheaper than a flagship phone.