Battery Monitor: Charge and Drain Rate

What the battery monitor shows

The big number is your battery level as the browser reports it. Below it you see whether the device is charging, on battery or fully charged. Time left becomes Time to full while charging. Rate is the change in charge per hour over this session, and the chart traces the level since you opened the page.

The rate needs a little time. Browsers report the level in whole percent, so the page has to see at least two changes before it can work out a rate. On a phone in use, that takes a few minutes. While charging fast it can take under a minute.

Testing a charger or cable

Charge rate is the easiest way to compare chargers and cables without extra hardware. Let the battery fall below about 50%, plug in, open this page and leave it for 10 minutes. Then try the other charger or cable with the same phone, at a similar level, with the screen at the same brightness. As a rough guide, a slow 5 W charger adds about 15 to 25% per hour to a typical phone, a 20 to 25 W fast charger 50 to 80%, and the fastest chargers more than 100% per hour in the first part of the charge. Charging slows down a lot above 80% to protect the battery, so compare at similar levels.

Finding what drains your battery

Unplug, open this page and note the drain rate with the screen on and nothing else running. Then use an app or game for ten minutes and check again. A phone idling with the screen on typically uses 5 to 10% per hour. Video streaming takes 10 to 15%, navigation with GPS 15 to 25%, and heavy 3D games 20 to 30% or more. If the idle rate is much higher, check the battery settings on your phone for an app running in the background.

Which browsers support battery information?

The page uses the Battery Status API. Chrome, Edge, Opera and Samsung Internet support it on Android, Windows, macOS, Linux and ChromeOS. Safari and Firefox removed it because websites were using battery level to track people across sites, so on iPhone, iPad and in Firefox the page tells you it cannot read the battery. To see battery health on an iPhone, go to Settings, then Battery, then Battery Health and Charging.

Battery health and the numbers here

Browsers report the charge level, not battery health. A worn battery still reads 100% when full, it simply holds less energy, so it drains faster. If your drain rates are much higher than the ranges above for the same use, and the phone is more than two or three years old, the battery may need replacing. Phone batteries usually keep about 80% of their original capacity after 500 to 1,000 full charge cycles.