Power Battery
Is your charger really fast?
How to test charging speed on Android · Updated October 2026
A charger that says "fast" on the box isn't always fast on your phone. The real charging speed depends on the adapter, the cable, your phone and even its temperature. Here's how to measure what you're actually getting, in watts.
Watts, volts and amps in one line
Charging power in watts = volts × amps. If your phone takes 9 V at 2 A, that's 18 W. Phones negotiate the voltage with the charger, and the battery decides how much current it accepts at that moment, so the number moves while you charge.
Why your charger is slower than the box says
- The cable. Thin or worn cables can't carry fast-charging current. A cable swap often makes the biggest difference.
- The adapter. Your phone only fast-charges with an adapter that supports its fast-charging standard.
- Battery level. Phones charge fastest at low levels and slow down a lot above about 80%. That's normal and protects the battery.
- Heat. A warm phone throttles charging to protect the cells. Charging while gaming is slow for this reason.
How to test your charger on Android
- Let the battery drop below about 50% so the phone can take full speed.
- Plug in the charger and cable you want to test, and keep the screen use light.
- Open Power Battery: the Home screen shows the live current (mA) and power (W), and the Speed Test rates the setup as fast, moderate or slow.
- Swap one thing at a time (cable or adapter) and compare. Keep the fastest combination.
What counts as fast?
| Live power | Typical meaning |
|---|---|
| 15 W and up | Fast charging is working. |
| 7–15 W | Moderate: a basic adapter, a weak cable, or the phone is warm or above ~80%. |
| Below 7 W | Slow: try another cable or adapter. |
These are rough guides; your phone's maximum depends on its model. The useful part is comparing your own chargers on the same phone.
▶ Test your charger — get it on Google PlayFrequently asked questions
How do I know if my phone is fast charging?
Check the live power while charging. Most phones show a few watts on a basic charger and well above 15 W when fast charging is working. Power Battery shows the live current and watts on its Home screen.
Why is my phone charging slowly with a fast charger?
Usually the cable, an adapter that doesn't support your phone's fast-charging standard, a warm phone, or a battery above about 80%. Swap the cable first.
Does fast charging damage the battery?
Fast charging produces more heat, and heat is what ages batteries. Phones manage this by slowing down near full and when warm. Avoid fast-charging a hot phone and don't leave it at 100% for hours.