i purchased iphone thirteen pro on tenth oct this year but it battery drained two percant in last five days.its battery health is hunderd per on eight dec but now its health decreasing two per is few days how to maintain it

Batteries degrade over time with usage, that's just how they work.

You can expect about a 1% drop per month with average use on an iPhone.

Apple recommends replacing it when it reaches 80%. To check your battery health, go to Settings > Battery > Battery Health.

iPhone Battery Replacement.

iPhone Battery Repair & Replacement - Apple Support

About Lithium Ion Batteries

iPhone Battery and Performance - Apple Support (IN)

Here are some tips on maximizing battery life.

Batteries - Maximizing Performance - Apple Batteries - Maximizing Performance - Apple