I think problem is not with battery because even after removing battery my lappi doesn't start quickly after hibernation. One thing more problem occurs not always but when my system is off for long time( more than 30 min).

Recovery from Hibernation is not a fast Process, It takes time to reload the files from the HDD. The Hibernation File is typically the same size as the installed Ram. In your case approximately 1014mb. Laptop HDD's are not Particularly fast either, 4500rpm is typical. In this case "quickly" is a relative term. What are you expecting? How long is it actually taking? Hibernation is intended to return you to What you were DOING as quickly as possible. It is not a FAST startup tool. When the Laptop will not be caried from place to place, try using Standby. It may or may not be faster. Definitely use Hibernation when moving the Laptop , taking it with you. There is nothing to learn from someone who already agrees with you.

It takes approximately 10-15 minutes to start even when i keep my lappi only on ac. Power light blinks for a second and after that it is off. I never move my lappi from one place to another.

Dumbob thanks for your help. But i have discovered that my problem exists even when i shut down my lappi. Do i reinstal OS?