Welcome to Android Central! Which phone? Charge up to 100%, then let it drain to 20-30% with normal usage, without charging in between. Then show us:
1. The main Settings>Battery screen.
2. The fullscreen battery graph screen (which shows Awake time and Cell Signal Strength).
3. The Screen category (to see total Screen On time).
4. The Cell Standby category, if present (to see Time Without Signal).
My phone is swipe elite star. It's battery backup is 2000mAh. Now when I charge my phone fully 100% then there is a sudden decrease in battery. For example, 85 or 90% left without usage. Please help.