Skip to content
Make It Last

Phone battery health, explained properly

By Editorial Team Published 2 min read
os android 16 / ios 26 tested 2026-09-09 retest 2027-03 by editorial team
Quick Fix
01 The single most useful habit: keep the battery roughly between 20% and 80% when you can. Deep 0→100% cycles and long spells at 100% in heat are what wear it out.
02 Check your current health in Settings (iPhone: Battery > Battery Health; newer Android: Battery > Battery health). Below ~80% capacity is replacement territory.
tested android 16 / ios 26 · 2026-09-09

Battery health gets buried under myths. Here’s what the numbers mean and what actually helps, based on how lithium-ion cells really age.

What a “charge cycle” is

One cycle = using 100% of the battery’s capacity, not necessarily in one go. Use 50% today and 50% tomorrow, both recharged, and that’s one cycle. Phones are designed for a set number — recent iPhones (14 and later) and Pixels (8a and later) target 1,000 cycles before capacity drops to 80%.

What “80%” means

Battery health is measured as maximum capacity versus new. Manufacturers consider 80% the point where a battery is worn — it still works, but runtime is noticeably down and the phone may slow or shut off unexpectedly under load. That’s when a replacement makes sense.

The habits that actually help

  • Stay between 20% and 80%. This is the single most evidence-backed habit. Deep discharges to 0% and long periods pinned at 100% both age the cell faster.
  • Prefer small top-ups over one big 0→100% charge. Multiple partial charges are gentler than full cycles.
  • Keep it cool. Heat is the number-one enemy — roughly every 10°C above ~25°C doubles the rate of chemical wear. Don’t charge under a pillow or leave the phone in a hot car.
  • Use fast/wireless charging when the phone is cool, not when it’s already warm.
  • Turn on the built-in optimisers — Optimised Battery Charging (iPhone), Adaptive Charging (Pixel). They hold at 80% overnight on purpose.

Myths worth dropping

  • “Let it drain to 0% to recalibrate.” No — deep discharges burn cycles. Occasional calibration isn’t worth routine full drains.
  • “Overnight charging overcharges it.” Modern phones stop at full and manage top-ups. The real issue is heat and time at 100%, which the optimisers mitigate.
  • “Closing apps saves the battery.” Usually the opposite — see our battery-drain guide.

When to replace the battery

Below ~80% health, or when the phone dies mid-day or shuts off in the cold, a battery replacement is one of the best-value repairs there is — as long as the phone still gets security updates. Check yours in the support tracker before spending.

Frequently asked questions

Can I see battery health on Android?

Newer Android versions show it under Settings > Battery > Battery health. Older phones don’t expose a percentage — a sudden drop in runtime plus warmth at rest is the tell.

Does fast charging damage the battery?

Occasional fast charging is fine; phones manage the heat. Doing it constantly while the phone is hot accelerates wear — so fast-charge when cool, trickle-charge overnight.

Is 100% health after a year normal?

Some phones sit at 100% for months then drop; that’s normal reporting behaviour, not a fault.

Sources