c600 randomly shuts down

So I have a dell c600 that I got free from work but it has some issue that I thought I could fix but it looks like it's not going to happen

The laptop randomly shuts down (all power settings are turned off) and this happens whether I let it sit in windows or on the bios screen.

I've read that it may be a motherboard issue since I was also having charging issues. So I replaced the motherboard, replaced the reserve battery and replaced the battery, all with supposedly new parts. Unfortunately all actions have failed to stop the random shut downs.

And it only seems to happen when running on battery.

Anyone have any other ideas?

 

I just finished a memory test and I had no errors.

Could it be that I just got a bad new battery?

 

Did you ever find a solution to the problem? I have the same problem with my Dell E1505. I know it's not the batery as I borrowed a friends (same laptop as me) and it does the same thing with his battery that works fine in his computer. Tried restoring back a couple months, updating every driver I could, bios updated, turning all power settings to always on, ran Dell diagnostic on everything, full virus/spyware/malware scan, checked M-Soft website for any relevant patches, everything short of replacing parts or wiping and reinstalling. Just bothers me it started randomly happening and only doing it on battery power. I don't believe temp is an issue for me either but will run coretemp or something to make sure. But fan sounds the same speed on AC as it does battery so not sure why it would die on battery and not AC.
Seen many posts with the same problem but no nbe has ever posted a solution or what fixed it for them. Any help or suggestions would be appreciated. Thanks.
-Tim