Answer:
The battery icon is slowly blinking:
Battery capacity is below 15%.
One grid is solid white:
Battery capacity is between 15% and 30%.
Two grids are solid white:
Battery capacity is between 30% and 60%.
Three grids are solid white:
Battery capacity is above 60%.
You can also check the exact battery level by looking at the number displayed below the battery icon.
For example, “99” means the battery is at 99% — nearly fully charged.