Why my laptop’s battery getting shorter.?

Question :I have asony PCGA-BP2E batteryand use in school and it is a travel battery. At the beginning of the year, the two put together will last up to 6 hours and ill just plug it in when i get home. And now, the battery seems to last only 3 hours, and i plug it in all night at home. What should i do to make the battery last longer again? Answer:charge it 100%, then let it die all the way several times. You may be able to erase its time memory this way. You probably messed it up in the first place by not letting battery fully die before you plugged it when you back in. You may have to get an new battery(Dell Latitude D520 battery , Dell Inspiron 3800 battery , Dell Inspiron 4000 battery , Dell Inspiron 4100 battery ), if you are still within warranty, you might be able to get one for free from the retailer or manufacturer.