A battery cycle is one full discharge/charge equivalent. Batteries typically retain 80% capacity after 500-800 cycles. Android 14/15 exposes this metric. On Samsung, it can be found via the SysDump utility (*#9900#) or external tools that read the mSavedBatteryUsage system log.
How Old Is Your Battery? Check the Cycle Count
The Problem: You want to buy a used phone or check if yours needs a replacement.
The Fix: Check the "Cycle Count" to see how much life is left.
Step-by-Step Guide:
Pixel: Go to Settings > Battery > Battery Health.
Samsung: Open the Phone dialer and type *#9900#.
Scroll down to open a "Battery Stats" or "SysDump" file (advanced).
Look for "Cycle Count." If it's over 500, you might notice reduced battery life.