Where to find your battery health information

Your device tracks how much charge your battery holds right now and how much it held when it was new. The difference between those two numbers is your battery health. On most phones and tablets, you can see this in Settings without installing anything or connecting to a computer.

On an iPhone, go to Settings > Battery > Battery Health & Charging. You will see a percentage labeled "Maximum Capacity" — that is how much charge your battery holds compared to when it left the factory. You will also see "Condition" which tells you whether the battery is Normal, Degraded, or needs Service.

On Android, the process varies by manufacturer. Samsung devices show battery information in Settings > Device Care > Battery, though the detail level depends on your phone model and Android version. Other Android phones may require you to dial *#*#4636#*#* to open a hidden diagnostic menu, or the information may only appear in Settings > About Phone > Battery Information. If you cannot find it in Settings, your phone's support page will show you the exact path.

Key Takeaways

  • Battery health is shown as a percentage of original capacity — 80% means your battery holds 80% of the charge it did when new.
  • iPhones display battery health in Settings > Battery > Battery Health & Charging; Android location varies by manufacturer.
  • A battery at 80% health is normal wear; below 50% usually means noticeably shorter time between charges.
  • Battery health degrades from normal use and cannot be restored, but you can slow degradation by avoiding extreme temperatures and keeping charge between 20% and 80%.

What the percentage actually means

A battery at 100% capacity holds a full charge. At 90%, it holds 90% of that charge. At 80%, it holds 80%. The percentage does not mean your phone will die at 80% — it means a full charge cycle (from empty to full) will take you 80% as far as it did when the phone was new.

If your phone originally lasted a full day on one charge and your battery is now at 80%, you might get through most of a day, but you will probably need to charge before bed. At 50%, you might get through half a day. At 20%, you might get a few hours of moderate use.

The exact impact depends on how you use your phone. Heavy use — constant video, gaming, or location services — drains the battery faster at any health level. Light use — mostly texts and email — means a degraded battery still lasts longer than you might expect.

Why batteries degrade and what you can control

Every time you charge a lithium battery, it loses a tiny amount of capacity. This is chemical wear, not a defect. A battery that goes through 500 full charge cycles typically drops to around 80% health. A battery that goes through 1,000 cycles might be at 60%. This happens to every rechargeable battery ever made.

You cannot stop this process, but you can slow it. Extreme heat and cold speed up degradation — leaving your phone in a hot car or outside in winter makes the battery age faster. Letting the battery drain completely and then charging to 100% repeatedly also accelerates wear. Keeping your charge between 20% and 80% most of the time extends battery life the most, though this is not practical for daily use.

If your phone is plugged in and fully charged, leaving it plugged in overnight does not degrade the battery further — modern phones stop charging at 100% and hold it there. But if you regularly drain to 0% and then charge to 100%, you are cycling the battery harder than necessary.

When battery health matters for your privacy and security

A degraded battery can affect your security settings. When a battery is very low on health, your phone may shut down unexpectedly even though the percentage shows 20% or 30% charge remaining. If you rely on your phone for two-factor authentication codes or security keys, an unexpected shutdown could lock you out of accounts when you need access.

Battery degradation also affects performance throttling. iPhones slow down the processor when the battery is very low on health to prevent unexpected shutdowns. This is a safety feature, but it means a phone with 40% battery health will run noticeably slower than one with 80% health, even at the same charge percentage. Slower performance can make it harder to notice if something is wrong — a malicious app running in the background, for example, or unusual network activity.

Signs your battery needs attention

If your phone shuts down when the battery shows 30% or higher, your battery health is probably very low. If your phone is hot to the touch during normal use, the battery may be degrading rapidly or failing. If you charge to 100% and the percentage drops to 90% within minutes of unplugging, that is also a sign of severe degradation.

In these cases, check your battery health in Settings. If it shows below 50%, you should plan to replace the battery or the device. Most phone manufacturers offer battery replacement for a fee — usually $50 to $100 — which is cheaper than buying a new phone and keeps your existing data and settings intact.

How to read the "Condition" status on iPhone

iPhones show a Condition field that says Normal, Degraded, or Service Recommended. Normal means your battery is healthy and you do not need to do anything. Degraded means the battery has lost enough capacity that you might notice shorter battery life, but the phone is still safe to use. Service Recommended means the battery is significantly degraded and Apple suggests replacement.

These statuses do not always match the percentage. A battery at 79% might show Normal, while one at 81% might show Degraded, depending on other factors like cycle count and temperature history. The percentage is more precise, but the Condition status gives you a quick sense of whether action is needed.

Checking battery health on older devices

Older iPhones (iPhone 6 and earlier) do not have a Battery Health menu in Settings. You can see basic battery information in Settings > Battery, but not the maximum capacity percentage. To check detailed battery health on older iPhones, you need to connect to a Mac or PC running iTunes or Finder and look at the battery information in the device summary.

Older Android phones vary widely. Some show battery health in Settings; others do not expose this information to users at all. If your Android phone is more than four years old and does not show battery health in Settings, it probably does not track this data in a way you can see. In that case, the practical test is how long your phone lasts on a charge — if it is noticeably shorter than it was a year ago, the battery is degrading.

Frequently Asked Questions

Can I improve my battery health once it has degraded?

No. Battery degradation is permanent chemical wear. You cannot restore capacity that has been lost. You can only slow future degradation by avoiding extreme temperatures and not repeatedly draining to 0% and charging to 100%. If your battery health is very low, replacement is the only way to restore full capacity.

Is it bad to leave my phone plugged in overnight?

Modern phones stop charging at 100% and hold the charge there, so leaving it plugged in overnight does not cause additional degradation. However, keeping your phone plugged in in a hot environment (like a car in summer) can speed up battery aging. For the longest battery life, unplug once fully charged if possible, but overnight charging is not harmful.

Why does my phone slow down when the battery is low?

iPhones intentionally reduce processor speed when battery health is very low to prevent unexpected shutdowns. A degraded battery cannot deliver power as quickly as a healthy one, so the phone slows down to match what the battery can provide. This is a safety feature, not a defect.

Should I replace my battery at 80% health or wait longer?

At 80%, your battery is normal wear and replacement is not necessary. Most people wait until the battery reaches 50% health or shows Service Recommended status before replacing. If you use your phone heavily and need all-day battery life, you might replace at 70%. If you use it lightly, you can go lower.

Can I check battery health on a phone that is not mine?

No. Battery health information is in the device Settings, which require unlocking the phone. You cannot see another person's battery health without their permission and their device unlocked. If you are buying a used phone, ask the seller to show you the battery health in Settings before you complete the purchase.