Depends on how long it is to remain on A/C while used. My dad's new Dell l'top suggests taking out the battery if the unit is more often used at home, on A/C power...Cyberianhusky said:Is it wise to leave a (fully charged) battery in a laptop while it is plugged into ac power plug. Will hurt or dimish the battery. Or is best use the ac plug and take the battery out while at home. I have a duo core chip.