Q: Are wireless chargers bad for smartphone battery life?
A: Virtually every device we own that runs on batteries — from smartphones and laptops to electric cars — use lithium-ion in its charging and discharging cycles. Understanding what can harm battery life and avoiding those situations is essential.
There are lots of theories on what helps to extend or diminish battery life, and much of it is in direct conflict.
An article published by ZDNet last year claimed that wireless charging will wear out the battery on the newer iPhones faster than if you were to use the charging cable.
While the author’s anecdotal review of his experience seems compelling, there are a lot of conflicting responses to what was clearly not a scientific study.
Charging by cable or via a wireless pad shouldn’t put your phone in a different situation while it’s charging, but how often you do it may have some potential effects.
Constant topping off
What does seem to be agreed upon by most experts is that constantly topping off your battery to 100% can shorten battery life because it puts your battery in a higher voltage state and higher heat conditions more often. Both of these are bad for battery life.
Lithium-ion batteries all have a battery management system (BMS) that helps to detect these harmful conditions and make adjustments to help reduce the impact.
Although the BMS is supposed to prevent improper voltages, it’s always best to use the charger that came with your device.
Some claim having your phone on a charger all night, every night also contributes to reduced battery life, but this is hardly something the experts agree upon. While the esoteric view is that the constant trickle charge can add stress to the battery, it’s just not practical to wake up in the middle of the night to unplug your phone from the charger.
If you can charge it before you go to bed and turn it off overnight, that will certainly remove it from any of the heat, high voltage or trickle charge issues.
Depth of discharge
Another area of agreement seems to be in how far you allow your battery to discharge. Batteries in iPhones are typically thought to have 500 complete charge cycles before going into a diminished charge state.
Constantly draining your battery to 0% will shorten the battery life, especially since you’re probably wasting charge cycles letting the battery drain when it’s not in use.
One study suggested that you increase battery life up to 400% when you don’t let your battery get below 50% before recharging.
The 500 cycles is an estimate and can range widely based on a number of variables, most especially heat. Apple introduced the battery health feature with iOS 11.3, which allows iPhone users to check what percentage of capacity their battery is estimated to have.
To access this information, go the Settings -> Battery -> Battery Health. Or if you want a lot more detail about the batteries in your Apple devices, check out a program called coconutBattery.
When you understand that you have a limited number of complete charge cycles, doing everything you can to reduce the number is the single best way to extend the life.
Unless you get a new iPhone every couple of years, it’s likely that your battery will diminish during its useful lifetime, but replacing the battery is far cheaper ($50-$70) than getting a new iPhone.