A mobile battery health check has three parts: read what the phone itself reports, run one simple runtime test, and look at the phone body for damage. No single number tells the whole story, so the three together give a fair answer on whether the battery is still good or due for a swap.
iPhone shows a Maximum Capacity figure. Many Android phones show less, and the menu names change from brand to brand. This page tells you what you can read, what you cannot, how far to trust it, and what to do next. If you need the battery code for a replacement, the hub on how to find the battery model name covers that part.
Quick facts
Step by step
Restart and update before you judge
Restart the phone and install any pending update in Settings. A stuck app or an old software bug can drain a healthy battery.
Open the battery page and search for health
Open Settings and tap Battery. If you do not see a health line, enter battery health in the search box at the top.
Read the usage list
On the battery page, look at which apps used the most charge. One app at the top with a huge share points to the app, not the cell.
Run the one-day runtime test
Charge to full, unplug, use the phone as you normally do, and note the time and percent when you reach 20 percent. Repeat on a second day.
Watch for sudden shutdowns
Note whether the phone switches off while it still shows 15 to 40 percent. This is a stronger sign of a worn cell than slow drain.
Look at the phone body
Place the phone on a flat table. If it rocks, the back cover gaps open up or the screen lifts at the edge, unplug it and do not charge it again. Do not press on the swollen part.
Decide and act
Two or more warning signs together mean a service visit. Ask for a battery test before paying for a new pack.
Five signs your battery is weak, and what each one means
Before you open any menu, think about what the phone has been doing in the last few weeks. A tired battery usually shows itself in daily use well before a number tells you.
| What you notice | Probable cause | Next step |
|---|---|---|
| Charge drops far faster than before | Cell has lost capacity with age | Do the runtime test below |
| Phone turns off at 15 to 40 percent | An aged cell struggles when the phone suddenly asks for a burst of current | Get the battery tested |
| Percent jumps, for example 30 to 10 in a minute | Weak cell or a wrong reading | Restart, charge fully, then test again |
| Phone gets warm while idle | Background app, weak signal or a faulty pack | Check usage list, then see a technician |
| Back panel gaps open or the screen rises at an edge | Cell has swelled | Unplug it and get it examined the same day |
If drain is your only complaint, read why the charge disappears quickly first, because apps and signal cause most such cases.
Mobile battery health check on Android: how to check battery capacity
Android phones do not share one common menu. The path depends on the brand and the software version, so treat the steps as a guide and not a fixed route. Open Settings, tap Battery and scan for an entry named battery health, battery status or battery information. Cannot find it? Type battery into the search field placed along the top edge of the Settings screen.
Some newer phones show a health level or a percent of original capacity. Some Samsung Galaxy phones with recent software show battery details under the About phone area, though this is not on every model. Many budget phones show nothing at all. That does not mean the battery is bad. It only means you must rely on the runtime test and the warning signs.
Do not use dialler codes for battery information unless the phone maker itself says they work on your model. Many do nothing, and some open service menus you should not touch.
For Samsung owners, the brand's own Samsung support page is the right place to look for help and service options for your model.
iPhone: reading Maximum Capacity
On an iPhone, open Settings, tap Battery, then Battery Health and Charging. On older iOS versions the line is called Battery Health. The screen shows a Maximum Capacity percentage. It compares the battery with a new one of the same model. A lower figure means the battery holds less charge than when new.
The same screen may also say whether the phone is managing peak performance, or show a message that service is advised. Apple rates its cells to hold up to 80 percent of original capacity after a stated count of full cycles, and newer iPhones get a higher count. A figure well below that, together with shutdowns, is a good reason to book a service visit.
Note that Apple speaks of capacity in watt hours and as a percentage, not in mAh. For model figures, see the iPhone battery capacity page.
Battery capacity tester and lithium battery capacity tester: what they are for
A battery capacity tester, sometimes sold as a lithium battery capacity tester, is a bench device. It charges and discharges a loose cell under control and then reports how many mAh it actually delivered. Service centres and some repair shops use such equipment on removed batteries. It is not something you plug into a sealed phone at home.
For a loose battery in your hand, a technician with such a tester can tell you whether the real capacity is close to the label. This is the best way to catch a fake pack that prints a big mAh number but delivers far less. A reading much below the printed figure on a new pack is a red flag, and the pack should go back.
Do not try to build a test rig yourself, and do not open or short a cell to test it. Leave this to people with the right equipment. To learn how the cells are built and why they wear, see mobile battery types.
Why a mAh figure on the screen can mislead
Some third-party readouts show a mAh number and call it your battery health. Treat it as a rough guide only. The phone estimates capacity from voltage and charge behaviour, and the estimate can swing after a software update or a deep discharge. Two readings on two days can differ by a wide margin on the same battery.
The printed capacity on the label is also not the same as what you get. Makers give a typical and a rated figure, and the real number falls with age. Use the on-screen number to see a trend, not to settle an argument. A phone that reports good health but shuts off at 30 percent still has a problem.
Do not install apps that promise to boost, clean or repair the cell. They cannot change the chemistry inside, and some only add background load. If you are comparing capacities between models, the battery capacity meaning page explains what the numbers stand for.
A simple runtime test you can repeat
This test needs only your normal day. Charge the phone to full, unplug it, and use it as you usually do. When it reaches 20 percent, write down the time. Do this for two days with similar use, same signal and brightness, and compare the hours.
An owner said his phone lasted till evening when new, and now dies by lunch. His two-day test showed about five hours from full to 20 percent, with the same apps. The battery usage list showed no rogue app, and the phone also shut down once at 25 percent. That mix of signs sent him to the service centre for a swap.
Make sure the test is fair. Poor signal while travelling, a hot car or a long video call can twist the numbers. When results jump around from one day to the next, run the test for a third day before you decide anything. Heat is bad for a battery. So is leaving the phone plugged in long after it shows 100 percent. Both wear it out sooner, so stay away from them while you track the results.
What to do after the check
If the signs are mild, you can often extend life by lowering screen brightness, taking a bulky cover off during charging and keeping the phone out of direct sun. If two or more strong signs show up, plan a replacement. On sealed phones, leave the opening to the maker's own service centre or an experienced repair technician.
Carry the exact model name and number, which you can read under About phone, and ask the technician to read the battery code on the old label and match it with the new one. Fitting and fake spotting are covered on our battery replacement page. If you are shopping for a new phone and want a bigger cell, see big battery phones.
A swollen body, strong heat, a leak or a dent means the battery may ignite. Disconnect the charger, handle the phone gently without pressing the bulge, set it on a hard, cool surface clear of anything flammable, and have a service point look at it soon. Cheap replacement packs often carry inflated capacity labels, so never trust the printed mAh alone. Check the code against your phone, the print quality, the weight and the batch details.
Frequently asked questions
How to check mobile battery health without an app?
Open Settings, then Battery, and look for a health or capacity line. If it is not there, use the Settings search box and enter the word battery. When the phone shows nothing, use the two-day runtime test and watch for sudden shutdowns.
How to check battery capacity in Android if there is no health option?
Many Android phones do not show it. Compare how long a full charge lasts now with how long it lasted when new, and note any shutdown above 15 percent. A service centre can test the battery properly.
What is a good Maximum Capacity on an iPhone?
Higher is better, and a new battery starts near 100 percent. Apple designs its batteries to keep up to 80 percent after a set number of charge cycles. If yours is much lower and the phone shuts down, book a service visit.
Can a battery capacity tester be used on a phone at home?
No. It is a bench device for loose cells, used by service centres and repair shops. At home, rely on Settings, the runtime test and visible signs on the phone.
Is a battery at 80 percent health bad?
Not always. If the phone still lasts your day and does not shut off suddenly, it can keep going. When daily use is hurt, or the phone turns off early, a replacement makes sense.