How to Check Your Phone Battery Health Before It Starts Dying at 30 Percent

Phone battery health is a number, not a feeling

Your phone battery health is the one number that tells you whether your phone is actually dying or just feels slow. On iPhone it is a percentage in Settings. On Android it is buried a little deeper, but it is there. Checking it takes two minutes, and it answers the question every phone owner eventually asks: is it time for a new battery, or a new phone?

Battery health measures how much charge your battery can still hold compared with when it was new. A battery at 100 percent health holds its full designed capacity. At 85 percent it holds 85 percent, which means your phone dies sooner even though nothing else changed. Lithium-ion batteries wear out with every charge cycle, and after two or three years of daily charging, most land somewhere between 80 and 90 percent.

How to check phone battery health on iPhone

Open Settings, then Battery, then Battery Health and Charging. The Maximum Capacity figure is the number you want. Apple considers a battery worn out below 80 percent, and iOS will tell you when service is recommended. Newer iPhones also show cycle count in the same screen, which is the number of full charge cycles the battery has been through. Anything above 500 cycles is well into the second half of the battery life.

If your iPhone is running iOS 17 or later, you can also see whether the battery is genuine Apple hardware and whether it has been replaced before. A phone that shuts down unexpectedly at 20 or 30 percent almost always has a battery health problem, not a software problem, and no amount of closing apps will fix it.

How to check phone battery health on Android

Android does not show battery health in one consistent place, so the steps depend on your phone. On Samsung phones, open Settings, then Battery and device care, then Diagnostics, then Battery status. On Pixel phones, open Settings, then Battery, then Battery health, where recent Android versions show an estimated capacity. On other Android phones, dial ##4636## in the phone app and look for battery information, though this code does not work on every device.

If your phone does not show the number natively, the free app AccuBattery estimates battery health by measuring charge over several cycles. It takes a few days of normal use to produce a useful estimate, so install it, use your phone normally, and check back. It is not perfect, but it is far better than guessing.

When to replace the battery, and when to replace the phone

Replace the battery when health drops below 80 percent, or when you notice shutdowns, swelling, or the phone dying fast even on light use. A battery replacement costs a fraction of a new phone: typically $50 to $100 at an official service center, less at a reputable third-party shop. It is the single best value repair in consumer electronics, and it can add two more years to a phone that is otherwise fine.

Replace the phone instead when the battery is only one problem among several: no more software updates, a cracked screen, a failing camera, or storage that is permanently full. If the phone still gets updates and does everything you need, a new battery is almost always the smarter spend. Back up your phone properly before any repair, and if storage is the other complaint, free up phone storage without losing anything first.

How to slow the wear

Batteries wear fastest at the extremes. Keeping your phone between 20 and 80 percent charge most of the time slows degradation measurably, which is why both Apple and Samsung now offer an 80 percent charge limit in settings. Heat is the other killer: do not leave your phone on a car dashboard, and take it out of a thick case while fast charging if it gets hot. Wireless charging generates more heat than a cable, so use a cable for overnight charging when you can.

None of this makes a battery last forever. Every battery is a consumable, and every phone owner will eventually face the replacement decision. The point of checking battery health is to make that decision with a number in front of you instead of a feeling. A phone at 89 percent health with a year of updates left is a phone worth keeping. A phone at 76 percent that dies at 30 percent is a phone that needs a $70 battery, not a $1,000 replacement.