I used to plug my phone in every night before bed and unplug it in the morning. Eight hours of charging, every single night. After about eighteen months, the battery would barely make it to 3 PM. I thought this was normal — phones just degrade, right?

Turns out I was doing the one thing that wears out lithium-ion batteries fastest: keeping them at 100% for hours every day. Here is how to actually charge your phone to extend its battery life.

Keep It Between 20% and 80%

Lithium-ion batteries are under the most stress at the extremes — below 20% and above 80%. The ideal range is the middle. Charge your phone to about 80% and unplug it. Do not let it drop below 20% before charging again. If you can keep your battery in this range most of the time, you can double its useful lifespan.

I started doing this with my current phone two years ago. The battery health is still at 93%. My previous phone was down to 78% by the same age.

Use Optimized Charging

Both iPhones and Android phones have an optimized battery charging feature. Turn it on. It learns your charging routine and holds the battery at 80% until just before you usually unplug, then tops it off to 100%. This minimizes the time your battery spends fully charged. On iPhone, it is in Settings → Battery → Battery Health. On Android, it is usually in Settings → Battery → Adaptive Charging.

Avoid Heat

Heat kills batteries faster than anything else. Do not charge your phone under your pillow, in direct sunlight, or inside a hot car. Remove the case while charging if your phone gets noticeably warm. Wireless charging generates more heat than wired charging — if battery longevity is your priority, plug it in.