1. How to check battery health on iPhone
On the iPhone it's very simple: go to Settings → Battery → Battery Health & Charging. There you'll see "Maximum Capacity", a percentage that compares your battery's current capacity with what it had when it was new. If it shows, say, 87%, it means your battery retains that percentage of its original factory capacity.
2. How to check battery health on Android
On Android there's no single menu that's the same across all brands, since each manufacturer customizes its own settings. Even so, many recent Samsung, Xiaomi, and other brand models include this information under Settings → Battery → Battery status (the exact name may vary slightly by model).
If your phone doesn't have that section, some devices let you access a system testing menu by dialing the code *#*#4636#*#* from the phone app, which shows technical information about the battery. Keep in mind this code doesn't work on all models or brands, so if nothing appears when you dial it, that menu simply isn't available on your phone.
3. What a low health percentage means
A value above 85-90% is considered a healthy, normal state for a phone with some use. Between 80% and 85% you already start to notice slightly less battery life, and below 80% it's common to notice a clear drop: the phone that used to last all day starts needing a charge by mid-afternoon.
When battery health drops a lot, it doesn't necessarily mean you have to replace the phone. If the rest of the device works correctly and you're happy with it, replacing just the battery at a repair shop is usually quite a bit cheaper than buying a new one, and it can give the phone several more years of life.
4. Physical warning signs without needing any menus
Besides checking the percentage in settings, there are signs you can spot without going into any menu, and that are worth watching for:
- The phone turns itself off even though the indicator still shows a considerable battery percentage.
- The back cover has swollen or bulged slightly.
- The screen has lifted or separated from the frame on one side.
If you notice either of these last two signs, stop using the phone immediately and take it to a professional repair shop as soon as possible. A swollen battery is a real safety issue, not just a cosmetic one: don't try to open the phone yourself and don't keep charging it in the meantime.