Phone battery health percentage: what's normal and when to replace it
Settings says your battery is at 84% health. Is that bad? Should you replace it now, or ride it out? The number is simpler than it looks.
What the number actually measures
A lithium-ion battery loses a little capacity every time it's charged and discharged, and a little more when it sits full or hot. The phone tracks how much charge actually goes in and out and compares it with the design capacity. One charge cycle is 100% of capacity used, whether that's one full drain or two 50% top-ups.
Where to find it
| Phone | Where to look |
|---|---|
| iPhone | Settings → Battery → Battery Health (& Charging). iPhone 15 and later also show cycle count in Settings → General → About. |
| Google Pixel | On newer models (Pixel 8a and later): Settings → Battery → Battery health. |
| Samsung Galaxy | Samsung Members app → Support / Diagnostics → Battery status (wording varies by version). |
| Other Android | Look under Settings → Battery; some makers show it, some don't. Avoid third-party apps that claim exact health from guesses. |
How fast does it normally drop?
Roughly: a few percent in the first months (some of that is the estimate settling), then slow and steady. A phone charged once a day does about 300–400 cycles a year, so dropping to the high 80s after one to two years is ordinary. Heat speeds it up most: charging under a pillow, gaming while charging, or leaving the phone on a car dashboard.
When to replace
- Below about 80%: the phone may show a “service” message and battery life will be noticeably shorter.
- Unexpected shutdowns at 20–30% or in the cold: a worn battery can't deliver bursts of power. (See phone dies in the cold at 30%.)
- Slowdowns: some phones limit peak speed to avoid those shutdowns.
- Swelling, a lifting screen or a gap in the case: stop charging it and get it replaced now. Don't press on it.
Use an authorised or reputable repairer; cheap unbranded batteries may report health incorrectly or not at all.
Slowing the drop
- Leave optimised or adaptive charging on, or set an 80% limit if your phone has one (why phones stop at 80% overnight).
- Avoid heat while charging, and take thick cases off if it gets hot (phone gets hot while charging).
- Don't worry about the odd full charge or running it low occasionally; habits matter more than single days.
Related
Why is my phone so slow? · Does fast charging damage the battery? · Power banks on planes: the 100 Wh rule · Phone battery drains overnight · Power bank mAh vs Wh · Why phones drain fast when travelling · Power bank calculator
Words explained on Wirebook: watt-hour · mAh · lithium-ion battery
Questions
Is 85% battery health good?
It's normal for a phone that's one to two years old. The battery holds about 85% of its original charge. Replacement is usually worth it below about 80% or if the phone shuts down unexpectedly.
At what battery health should I replace my phone battery?
Around 80% or below, or sooner if the phone shuts down unexpectedly, slows down, or the battery swells.
How do I check battery health on Android?
On Pixel 8a and later go to Settings, Battery, Battery health. On Samsung use the Samsung Members app's battery diagnostics. Other makers vary, so look under Settings, Battery.
Why did my battery health drop so fast?
Heat is the biggest cause: charging while gaming, under a pillow or in a hot car. The first months can also drop faster as the estimate settles.
Does charging to 100% ruin battery health?
Not by itself, but sitting at 100% for hours, especially when warm, wears it a little faster. Optimised charging or an 80% limit reduces that.
Published .