Why noname USB chargers can kill and branded one are safer: looking at their insides

In November 2019 a 17-year old thailand girl died while charging her phone. In October that year a 25-year old man was killed by a phone charger. In May 2019 a 22-year old man was killed in sleep by a charger. In December 2018 while charging her phone died 15-year old pancration champion. 

News outlets regularly report about death, which happenned while charging phone, and usually a third-party wall charger is blamed for. But what specifically is dangerous, and how safe charger is different from a dangerous one? Disassembly of a few original adapters that were supplied with phones, and a few third-party devices answered this question.

What is dangerous

Electricity is very dangerous for humans and, at certain circumstances, a person can be killed by such a small amount of energy that a smartphone will not even notice. For example, modern smartphones are charged with a current of 2 amperes or more, and for humans, the lethal current is 0.1 amperes. A current of 0.01 amperes through the body will feel like a very painful shock.