Phone batteries are lithium-ion, and every one of them slowly loses capacity as it goes through charge cycles. After a few years of daily use, most phones hold noticeably less charge than they did when new. Here's how to tell when it's time for a replacement.
Common signs of a worn battery
- It drains much faster than it used to. If a phone that once lasted all day now needs a top-up by mid-afternoon with similar use, capacity has probably dropped.
- It shuts off with charge remaining. A worn battery can't deliver peak power, so the phone may switch off suddenly at 20% or 30%, especially in the cold.
- It feels slow. Some phones reduce performance to prevent unexpected shutdowns when the battery is aged.
- The percentage jumps around. Dropping from 40% to 10% in minutes is a classic sign.
- The phone gets hot while charging or during light use.
- The screen or back is lifting. A swollen battery can push the screen or back panel out. Stop using and charging the phone and get it looked at. Swollen batteries can be a fire risk.
How to check battery health
- iPhone: go to Settings > Battery > Battery Health & Charging. Apple considers a battery worn when maximum capacity falls below about 80%, and the screen will say if service is recommended.
- Android: this varies by manufacturer. Many Samsung phones show battery information in the Samsung Members app under diagnostics, and some Pixel models show it under Settings > Battery > Battery health. Search your phone's settings for "battery health".
Tips to slow battery wear
- Avoid leaving your phone in a hot car or in direct sun. Heat is one of the biggest causes of battery wear.
- You don't need to drain it to 0% before charging. Frequent partial charges are fine.
- Turn on optimized or adaptive charging if your phone has it.
- Use a good-quality charger and cable.
If your battery shows several of these signs, replacing the battery is often much cheaper than replacing the phone.