Inspiron mini 10 Running on battery even when a/c is plugged in restart computer and plug in a/c again and charges up but then drains battery again

Ifthe laptop battery is more than 3 - 4 years old then the battery could be wornout. Rechargeable batteries have a finite number of charge and discharge cyclesand will lose their charge capacity over time, i.e. won't charge to 100% andgradually the charge reduces until the battery won't charge up atall. ORThe battery shows a 100% charge but when the adapter is disconnected the batterydrops off to zero capacity in a very short time. Ifthe battery drops to an unacceptable charge level then the battery needs to bereplaced.