T42 boots on AC but not with battery installed ?

[RRHODY]

I have a TYPE 2373 T42 trying to restore. It will boot to BIOS with AC plugged in but if I put a battery in - it won't boot. There's no resonse to the power button. The battery has been working in another T42 I think I've seen this problem discussed but didn't find any posts in my searches.
Can someone direct me to those previous posts - or - solve this situation?