How to Test Phone Battery Health
When buying a used phone, battery health is one of the most critical factors. A degraded battery means you'll be tied to a charger and experience unexpected shutdowns.
What this tool checks:
- Current Percentage: Real-time readout of the device's battery level.
- Charging State: Plug in a charger and verify that the port actually works and is passing power to the device.
- Time to Full: If supported by the OS, this shows the estimated time remaining until the battery is 100% charged.
Pro Tip: The 5-Minute Charger Test
When inspecting a used phone in person, plug it into a portable power bank for 5 minutes. Use this tool to watch the percentage. If it goes up 5-10% and the phone doesn't get uncomfortably hot, the charging IC is likely healthy.
Need to replace a bad battery?
If your phone's battery health is below 80% or drains rapidly during testing, it's time for a replacement. We recommend high-quality replacement kits that include the necessary adhesive and prying tools.
Frequently asked questions
What is a good battery health percentage?
80% or higher is considered healthy. Apple designs iPhone 15 and newer batteries to keep 80% capacity at 1,000 full charge cycles, and earlier models at 500 cycles. Below 80% you'll notice shorter battery life, and Apple recommends a replacement.
How do I check battery health on Samsung Galaxy?
On recent One UI versions go to Settings › Battery › Battery information to see the condition. You can also open Samsung Members › Get help › Phone diagnostics › Battery status, which rates the battery as Normal, Good or Weak.
Why does my browser not show battery details on iPhone?
Safari does not share battery information with websites. Open Settings › Battery › Battery Health & Charging on the iPhone itself to see Maximum Capacity and cycle count on supported models.
What are signs of a swollen battery?
The screen lifting from the frame, the back cover bulging, the phone rocking on a flat table, or creaking when pressed. Stop charging a phone with a swollen battery and have the battery replaced right away. Do not press on it or puncture it.
How much does a phone battery replacement cost?
Apple charges roughly $89 to $119 out of warranty for recent iPhones. Samsung authorized repair typically costs $70 to $110. Independent shops can be cheaper, but check they use quality cells and give a warranty.
How can I make my battery last longer?
Avoid heat, don't leave the phone at 100% on a charger overnight for months at a time, and enable Optimized Battery Charging (iPhone) or Protect battery (Samsung, which limits charging to 80% or 85%). Keeping the charge between about 20% and 80% reduces wear.