You can check the battery's current capacity by running powercfg /batteryreport at a command prompt with admin privilege, but if this is the original battery, it's pushing five years old and likely on its way to needing a replacement.

PCIe Solid-State Drive M.2 2280 SSD PCIe Gen 3x4 NVMe, This type of storage is in my latitude 5500. I want to install OS in my laptop. But I am confused about what to select in Sata operation. Because when I got this laptop(used from market) it was selected to AHCI but in data sheet of this model the default sata operation selected is Raid On mentioned

You asked about a battery -- and now about installing the operating system?

RAID ON is the Dell default, but will require you to pause the install when indicated and have the Intel RST driver ready on a flash drive, or the installer will not see the drive.  In AHCI mode, no added driver is needed.

If you need the F6 driver, it's here;  otherwise, the choice is yours (but if you're expecting a clean OS install to fix the problem of an aged battery, it won't).

https://www.intel.com/content/www/us/en/download/19512/intel-rapid-storage-technology-driver-installation-software-with-intel-optane-memory-10th-and-11th-gen-platforms.html

@ejn63​ I am getting 6 hr+ backup of this battery. I guess it is a battery software fault its giving incorrect information to the OS, because if my battery is dying due to its ending life cycle then it should not give that much backup. Do I need to perform calibration? 

I am satisfied with the battery backup but the issue is the incorrect information about the battery level.