To rectify it you need to narrow the scope of the trouble. 

It's possible it may be an issue with Windows or with the Battery (i guess battery first). You might check out a Linux (Ubuntu) LiveCD. If the same problem exists with the LiveCD, then it's definitely a hardware issue. After identifying it as a hardware issue then replace the battery. If the problem doesnt exist using the LiveCD, then there is an issue with Windows and a reload may resolve it. If you tell us which model laptop, we may be able to identify a known issue with that battery (seems like my wife's Inspiron 15xx has trouble per the reviews of replacement batteries on Dell's site).

Laptop Battery does not show true charging level
What is the difference between Cajun and Creole cuisine?
