Most people leave their phones on their chargers overnight, but sometimes you end up at 5% halfway through the day and need to top off your battery. Fast charging is very convenient in such circumstances, but it may be damaging your smartphone’s battery and reducing its capacity over time. To find out if that does happen, GreatScott! used Arduino to test fast charging on several smartphone batteries.
Lithium batteries aren’t susceptible to the same degradation issues that were common for NiCad batteries, but that doesn’t mean they are impervious to damage. GreatScott! suspected that fast charging stresses Li-Ion batteries and diminishes their capacity. To test that idea, he needed to put batteries through many charge and discharge cycles. For this experiment, he had a control group charging with the typical 1A of current and another group fast charging at 5A. Both groups discharged at a constant 1A and went through 100 cycles.
Charging and discharging six batteries 100 times each is a time-consuming task, so GreatScott! designed custom devices for the job. Each is a custom PCB populated with an Arduino Nano board, an OLED screen, lithium charging circuitry, and the discharge circuit. That discharge circuit utilizes an op-amp to convert a constant 1A into waste heat. The OLED shows the battery voltage at any given time and the number of charge cycles.
These test devices let GreatScott! gather valuable data. The batteries charged at 1A didn’t suffer any substantial capacity loss, but the batteries charged at 5A lost an average of 1.6% of their capacity. That was after only 100 cycles, so the loss would get much worse over the course of years. GreatScott! concluded that it is best to avoid fast charging and to only use it when necessary.
