How to check your phone’s battery health (and when to replace it)

A phone battery wears out slowly. After a year or two it holds less charge, and the phone lasts less time between charges. Checking its health tells you whether the battery is the problem, or whether something else is draining it.

iPhone

Open Settings > Battery > Battery Health & Charging. The page shows Maximum Capacity, which compares the battery’s current capacity with when it was new. A lower number means fewer hours between charges. Some newer iPhones with recent iOS versions also show more details, such as the cycle count.

Android

There is no single place, because each maker does it differently.

• Look in Settings > Battery (or “Battery and device care”) for an entry such as “battery health” or “battery information”.
• Many brands also have a care or diagnostics app from the maker that can test the battery. Check which one your phone has.
• Some phones show nothing at all. In that case, judge the battery by the signs below, or ask the brand’s service centre to test it.

What the percentage means

The percentage is how much of the original capacity is left. Many guides, including replies on Apple’s own community pages, treat about 80% as the point where replacing the battery is worth considering. It is a rule of thumb, not a strict limit, so a phone with a lower number can still work well if you do not need long days away from a charger.

Signs of a worn battery

• The battery drains much faster than it used to.
• The phone shuts down at 20% or 30%.
• The phone gets hot when you are not using it.
• The phone is slow or restarts when the battery is low.
• Stop using the phone and take it to a service centre if the battery swells, the back lifts or the phone smells of burning.

Before you blame the battery

Check what is using it: a rogue app, a weak signal or a bright screen can look like a bad battery. Our guide how to make your phone battery last longer covers the settings that matter, and charging myths, sorted explains what actually wears a battery.

When to replace it

• If battery health is low and the phone no longer lasts your day, a replacement is often cheaper than a new phone.
• Use the brand’s official service centre where you can. A cheap, low-quality battery can be unsafe.
• Ask about the price and the warranty on the new battery before you agree.

If you are buying a used phone

Ask the seller to show the battery health screen before you pay, and look at the signs above. See our used phone checklist.