Weird thing happened the other day. I had my laptop off the charger running on battery power for a short while. I decided to charge the battery, so I plugged it back to the AC adapter. I checked on it a couple of hours later and the charge had not moved from the 80% it was at when I plugged it in. I then thought my battery was going bad so I replaced it with my spare battery which was at only 20%. I let that sit for a few hours and when I checked on it, it also had not charged a bit. I then thought it must be my adapter. I have a few of these and tried all of them throughout the next couple of days and none of them charged either battery as well. Also, when I remove the battery with the laptop plugged in, my laptop stays on. Therefore, I feel it is not the battery or the charger so what could it be? My laptop is a Dell Latitude C640. Please help!