Samsung recalled their new Galaxy Note 7 smartphones last year after some of their lithium ion batteries overheated and either caught fire or swelled and caused other damage. The amount of batteries having problems was quite small in proportion to the amount manufactured, but once the reports got out, the resulting bad publicity constituted a fire of its own that Samsung needed to extinguish. Lithium ion batteries overheating and causing damage or dangerous fires is nothing new, and the problem is not limited to the batteries in Samsung smartphones or particularly in the Galaxy Note 7. What is relatively new are the quick charging and wireless charging features of some newer smartphones, including the Galaxy Note 7.
Back of lithium ion battery,
showing safety warnings;
photo by Solomon203.
As batteries go, lithium ion types are particularly volatile and susceptible to malfunction from mishandling or careless manufacturing. That has been the trade-off for batteries that are lightweight, relatively energy dense, and capable of going through hundreds or even thousands of charging cycles without suffering from the memory defects of previous compact battery types like nickel cadmium. Consumer demand is for long battery life combined with quick charging, in a phone that is slim and light, and in the past few years cell phone manufacturers have responded by including quick charging and wireless charging features, while maintaining or even increasing battery capacity.
Wireless charging, while it has many benefits such as the capability of being a universal method of charging that eliminates dependence on proprietary wired chargers, is relatively inefficient and therefore loses more power to heat than wired chargers. Heat is bad for batteries, particularly lithium ion types. Quick charging technology that can add a 50% charge to a phone’s battery in 15 minutes requires strict attention to software design in both the charger and the phone to monitor the process, lest it cause overheating. Think of how it is possible for a NASCAR pit crew to dump over 20 gallons of fuel into a race car in less than 10 seconds using only gravity and special attention to venting, and do it safely, and then think of how complex the monitoring system must be for quickly charging a smartphone battery – which includes a flammable electrolyte – when you consider that charging introduces electricity into an essentially chemical process. It’s a wonder the proportion of failures isn’t higher than it is.
It turns out the defect in the Samsung Galaxy Note 7 was largely a design error of squeezing too large a battery into the phone. Or the compartment in the phone was too small for the battery. Either way, because of the tight fit the positive and negative plates within the battery got closer to each other than they should, overwhelming the separators meant to keep them apart, and causing some of the batteries to overheat to a disastrous degree. No doubt Samsung’s corporate culture is to blame for this, because unlike other manufacturers they test their batteries in house, and in this case they were rushing to compete with Apple’s impending release of the iPhone 7. The design error was either overlooked in the rush or considered not serious enough to warrant a redesign delay that might keep Samsung from beating out their chief competitor in the smartphone market, Apple. Whatever the issue was, this time Samsung’s attempt to get a jump on Apple backfired.
Alessandro Volta’s battery on display
at the Tempio Voltiano Museum
in Como, Italy; photo by GuidoB.