Battery is the one part of a phone that is guaranteed to be worse than it was on day one. Everything else either works or it doesn't. That makes battery health the number worth asking about — and the number most sellers avoid putting in writing.
What "battery health" actually measures
It is the share of the original capacity the battery can still hold. A phone at 90% holds nine tenths of the charge it held when it was new. On an iPhone you can see it yourself under Settings → Battery → Battery Health & Charging. Android phones vary, but the figure exists underneath and testing tools can read it.
Apple designs iPhone batteries to keep about 80% of their capacity after 500 full charge cycles, and 1,000 cycles on the iPhone 15 and newer. That is why 80% is the number that keeps appearing: it is where the manufacturer itself says a battery has reached the end of its rated life, not where the phone stops working.
What each band means in practice
| Band | What to expect |
|---|---|
| 90% and above | Close to a new phone. Most people never think about the battery. |
| 85-90% | A noticeably shorter evening if you are a heavy user. Fine for most. |
| 80-85% | A top-up during the day if you use the phone hard. The cheapest healthy option. |
| Below 80% | Plan on charging daily, or budget for a replacement battery. |
How much is a higher band worth?
A battery replacement costs somewhere between $50 and $90 for most models. So if the gap between an 85-90% phone and a 90%+ phone is $20, the higher band is good value. If the gap is $80, buy the cheaper phone and replace the battery later if it ever bothers you — you will end up with a brand new battery for the same money.
What to watch out for
- "Good battery" with no number. That is a word, not a measurement.
- A number with no date. Battery health drops as the phone is used. A reading from six months ago is not the phone you are buying.
- A brand-new battery in an old phone. That is fine, and often better — but the seller should say whether the cell is original or aftermarket, because they don't age the same way.
How we handle it
We measure battery health before a phone ships and sell it by band: 90%+, 85-90%, 80-85% or below 80%. You choose the band on the product page and the price moves with it, so you are never paying for a number you can't see. Every phone also passes a 32-point test, and comes with a 12-month warranty and 30 days to return it.
Browse what we have in stock on the all phones page, or read the full buying guide.