You may have heard that you should keep your phone between 40% and 80% charge. Here’s what that “40–80 rule” actually means — and whether it’s worth following.
The idea behind the rule
Lithium-ion batteries wear faster when they spend a lot of time at very high charge (near 100%) or are often drained very low. Staying in the middle range puts less stress on the battery, which can help it keep more of its capacity over time.
iOS already does some of this for you
- Optimized Battery Charging learns your routine and holds the charge at 80% overnight, finishing just before you usually unplug.
- On newer iPhones you can find extra charging options under Settings › Battery › Charging, including limiting charging to 80%.
Practical tips that matter more
- Avoid heat. Heat is the biggest enemy of batteries — don’t leave your phone in a hot car or charge it under a pillow.
- Don’t panic about occasional full charges. Charging to 100% before a long day is fine.
- Use a good charger and cable. Cheap, damaged cables can cause unstable charging.
- Don’t run it to 0% regularly. Plug in when you get low.
When the battery is already worn
No charging habit can bring back lost capacity. If Settings › Battery › Battery Health shows around 80% or lower, or your phone shuts off with charge left, it’s time for a new battery. Read our guide on when to replace your iPhone battery, or see iPhone battery replacement at Avenue D Cellular — from $49, usually done while you wait.