why chargie works
The science behind
A typical smartphone charges up to 100% and then keeps the battery in that very high state (around 4.35 volts) until the user disconnects from the mains.
The battery is indeed protected from thermal runaway by its internal circuitry (it would catch fire otherwise), but the measures taken happen at extreme values, and are not optimized for a long and sustainable battery life.
Holding a 100% charge for many hours at a time induces a voltage- and heat-related stress and damages the internal lithium lattice of the battery, at a molecular level (see reference).
Limiting the charge level below 100% or releasing it once it has topped up has hugely beneficial effects for the lifespan of the battery.
An optimized charging process can take a normal phone battery from 250 cycles to more than 1000, before it shows signs of degradation (tables courtesy of batteryuniversity.com ).
This has been well documented by the scientific community. Electric car manufacturers like Tesla already avoid charging to 100% by default. They say it’s fully charged, but it’s actually less. Microsoft has even implemented charge limiting in Surface tablets , Sony in latest-generation Xperia and Lenovo in laptops. Apple has recently implemented a similar but way less configurable function in iOS 13.
However, most phone manufacturers haven’t and probably never will.
Practically, it is best if you can keep the charge between 20% and 90%. If you do so, Chargie will apply the hysteresis you set, and the practice will yield much better results in the long run, from both a battery lifespan and daily usability perspective.
Ideally, the lower the daily charge, the better it is for the battery. However, you should take care not to overdischarge the battery either. For example, if you regularly go down to 1%, it’s better if you set the top up level to 100% for the morning. Chargie will keep the base level at 60% and will only stay at 100% for a brief period of time.
By applying hysteretic charging, the risk of battery swelling and fires is greatly reduced (unless the battery itself has a physical defect). Google this.