Compaq presario wont keep correct system time

Compaq Presario 2210us laptop.
XP Home.

Computer came into shop wasn't keeping correct system time. I figured it was a dead BIOS battery. I took the laptop apart and replaced the battery. Should solve the problem right? Wrong. It keeps the correct time when it is on and booted into windows. If I turn off or restart the machine when it is on AC power it will keep the time thru a reboot or being turned off overnight. The problem is when I either reboot or turn the machine off without being plugged into AC power it looses the correct time. Most of the time it will have the time it was shut off or rebooted as the time.

I tried to repair the W32 time and also tried a third party sync software to sync with a time server. This works, but only if connected to the internet. I'm totally out of ideas and really need some help!

Thanks all!

 

I have the same problem with my Compaq Presario F572US notebook PC, running Vista Home Premium. If I shutdown overnight with main battery out and AC power adapter not plugged in, it will lose time. In my case, the time is usually a few hours after I shutdown, not the time it was shut off, but still hours behind.

I have not replaced the CMOS/BIOS battery. Last time I checked, I found they cost more than I had hoped, around $36. So, I just reset time as needed.

I don't believe my notebook PC ever kept time with main battery out an AC adpater unplugged overnight. I just wasn't aware of it during the first year because I always left the main battery in. I wish I had know while it was still under warranty.

Do you know whether the laptop you're working on ever kept time with main battery out an AC adpater unplugged overnight?

Are you sure you got the right battery for it? Can you test the battery?