Phone battery advice is a museum of myths — “drain it fully”, “never charge overnight”, “close all your apps”. The chemistry has opinions, and they are simpler than the folklore. Here is what actually preserves a lithium battery, and what just wastes effort.
How the battery actually ages
A phone battery is rated in charge cycles, but aging is driven by three things: how full it gets, how hot it runs, and how empty it goes. Voltage stress at the extremes (100% and 0%) is what degrades the cells — not some mystical memory effect that died with NiCad in the 1990s.
The rules that matter
- Charge in the 20–80% band when convenient. Not religiously — but batteries that live in the middle outlive batteries pinned at 100% on a hot dashboard.
- Use the built-in charge limiter. iPhone’s “80% limit” and Android’s “charge limit” features do this automatically. Turn one on, forget about it.
- Heat is the real killer. Charging while gaming in the sun does more damage in a month than a year of ordinary charging. Off the case, out of the sun, off the pillow.
- Slow charging is fine; fast charging is also fine. Modern fast-charge systems manage heat well. The difference is smaller than the marketing suggests.
The myths, retired
- “Drain it to 0% sometimes.” Harmful, not helpful. Deep discharges stress the cells.
- “Close all apps to save battery.” Modern phones suspend apps; force-closing them makes reopening cost more energy than it saves.
- “Overnight charging destroys it.” Phones stop at 100%; the harm is sitting at full charge for hours — which the 80% limiter solves properly.
- “Third-party chargers kill batteries.” Certified ones are fine; the $3 gas-station special with no certification is the actual risk.
When replacement is the answer
Batteries are consumables: after 500–800 full cycles, 80% health is normal. When your day ends at 6 pm on 20%, a $50–80 battery replacement restores the phone for another two years — a far better deal than the upgrade treadmill. Check cycle count and health in settings before deciding; our approach to electronics value applies to repair-versus-replace decisions too.