Battery health is one of the most overlooked but critical factors when buying a second-hand phone. A phone with a degraded battery may last only a few hours on a charge, no matter how powerful the processor. Here is how to check battery health on every major platform.

What is battery health?

All phone batteries degrade over time with charging cycles. Battery health is expressed as a percentage of the battery's original maximum capacity. A brand new phone starts at 100%. After 500 full charge cycles, a typical lithium battery retains around 80% of its original capacity.

A phone at 80% battery health will last about 20% less on a charge than when it was new. At 70% or below, degradation becomes very noticeable in daily use.

Battery health scale — what to look for

What the percentage means

95–100%Excellent — practically new condition
85–94%Good — solid battery life, no issues expected
80–84%Acceptable — noticeable reduction but still usable
70–79%Poor — significant degradation, negotiate price down
Below 70%Avoid or factor in battery replacement cost

How to check on iPhone

Settings → Battery → Battery Health

  1. Open Settings
  2. Tap Battery
  3. Tap Battery Health & Charging
  4. The percentage shown is the maximum capacity relative to when the phone was new

Apple recommends battery replacement when health drops below 80%. At that point, iOS may also enable performance throttling to prevent unexpected shutdowns.

How to check on Samsung

Device Care or hidden diagnostic menu

  1. Open Settings
  2. Tap Device Care (or Battery and Device Care)
  3. Tap Battery
  4. Samsung shows battery status here — "Good", "Normal", or "Replace soon"

For a more precise percentage, dial *#0228# on Samsung devices. This opens a hidden diagnostic menu showing exact battery capacity readings.

How to check on other Android phones

Using a third-party app

Most Android phones outside of Samsung do not show battery health natively. Use a trusted third-party app such as AccuBattery (free) which measures real-time capacity over charging cycles and gives an accurate health percentage. Install it, charge the phone fully, and the app will display the health reading.

What if the battery health is low?

A low battery health reading does not necessarily mean you should walk away — it depends on the price. Battery replacement for most iPhones costs $50–100 at Apple or a third-party repair shop. For Android phones it is often less. Factor this into your negotiation: if a phone has 75% battery health, ask for a corresponding price reduction or request the seller replace it first.

Check the IMEI too

Battery health is important — so is verifying the IMEI matches what the seller claims. Do both before buying.

Free IMEI Check →