Battery testing

iPhone battery

Settings > Battery > Battery Health shows Maximum Capacity. Follow the steps in the iPhone guide, including Parts and Service History to see if the battery was replaced.

Android battery

Android phones do not all show a battery health percentage. Samsung Members > Diagnostics has a battery check on Galaxy phones. Some Android phones show battery information under Settings > About phone or Settings > Battery. What you see depends on the brand and the Android version.

AccuBattery and similar apps estimate capacity from how much charge goes in over several charges. They need several full charging cycles, so on a phone you try for ten minutes they give no reliable number.

Warning. An Android app's battery number is an estimate, not a figure certified by the maker. Do not pay or refuse a phone because of one app's number.

A 10 to 15 minute test you can do in the shop

1. 1Note the battery percentage and make sure the phone is not in low power mode.
2. 2Play a video at medium brightness for 5 minutes. Note the drop. As a rule of thumb (not a maker figure), a steady drop of 1 to 3% is normal and a quick drop of 5% or more is a warning.
3. 3Feel the phone. Warm is normal. Hot to touch while idle or on video is a warning.
4. 4Plug in an original charger and cable. Charging should begin within a few seconds, and the percentage should rise steadily for 5 minutes without stopping and starting.
5. 5Look at the phone from the side and the back. A screen lifting from the frame, a gap, or a bulging back can mean a swollen battery.
6. 6Restart the phone and ask if it ever turns off by itself. Sudden shutdowns at 20 to 40% are a typical sign of a weak battery.

Warning. A swollen battery is dangerous. Do not charge it, and do not buy the phone.

Signs the battery was replaced

1. 1iPhone: Parts and Service History shows Unknown or Used for the battery, or Battery Health says it cannot verify the battery.
2. 2Any phone: screws with damaged heads, a back cover that does not sit flat, glue marks, or a very high battery health on a phone that is several years old.
3. 3Ask directly. A replaced battery is not a defect if the price reflects it and the part is good.

Common questions