When laptop battery has passed a certain number of charge/discharge cycles, its capacity decreases and it can't provide a lot of power. Worse yet, the battery gives incorrect info on its capacity. Usually it looks as follows. The battery discharging normally down to certain level. For example, down to 60%. Then there is a sudden drop of the counter down to 5 % and the battery signaling that the remaining charge is just for 1 minute only, while actualy the remaining time is more then 1 hour. Naturally, its not comfortable to work with such battery. You can never know how long you can work and the only wayout is just to replace the battery.