The battery is the part that wears most in a phone and the one that affects your day-to-day experience the most. So when you buy refurbished, it's worth knowing how to check it and what to expect. It's easier than it sounds.
What you need to know first
Lithium batteries lose capacity with every charge cycle (one cycle equals using 100% of the battery, even if spread over several charges). As a reference, Apple considers a battery worn when it drops below 80% of its original capacity. Above 85%, in practice, the difference from a new one is small.
How to check it on an iPhone
- Open Settings → Battery → Battery Health & Charging (the name may vary slightly by iOS version).
- Look at Maximum Capacity: it's the percentage compared with when it was new.
- If you see a service message or an "unknown part" notice, it may indicate a non-genuine or heavily degraded battery.
On iPhone 15 and later, under Settings → General → About you can also see the cycle count, the manufacture date and the date of first use.
How to check it on Android
It depends a lot on the manufacturer:
- Samsung: open the Samsung Members app → Support → Phone diagnostics → Battery status.
- Google Pixel: on recent models, under Settings → Battery → Battery health.
- Other brands: search for "battery" in settings. If there's no health information, third-party apps such as AccuBattery give an estimate after a few charge cycles.
A practical test in the first few days
Beyond the percentage, see how it behaves:
- Do you make it to the end of the day with your normal use?
- Does it switch off suddenly with 15–20% left? Bad sign.
- Does it get very hot while charging or with light use?
- Is the back swelling or the screen lifting? Stop using it and make a claim immediately.
What to do if the battery isn't right
- Within the returns period: if you're not happy, send it back. We explain how in warranty and returns.
- Below the guaranteed minimum: contact the seller and claim under the warranty.
- Out of warranty: a battery replacement at a repair shop usually costs far less than a new phone and adds years of life.
How to look after it from now on
- Turn on Optimised Charging (iPhone) or battery protection (Samsung and Pixel), which limit charging to 80–85% when you don't need more.
- Avoid heat: don't leave it in the sun or charge it under your pillow.
- There's no need to run it down completely: modern batteries prefer partial charges.
In short
Check the maximum capacity as soon as the phone arrives, watch how it behaves during the first week and don't hesitate to use the returns period or warranty if it falls short. That way, the battery stops being a lottery.