Weird all of the m700s i've worked on and the one with a pIII 450 i own work without batteries. I've also seen alot and also been plauged by battery issues too. Seems the voltage regulator on that particular laptop has a history of failure, this might be your problem only more extreme, replacement of that part might be your solution. I've given up trying batteries and just use AC now and only use the laptop hooked up to a scanner to scan stuff when i need to.
R.I.P Rangeral, To one of HWC's best moderators and a great guy
By the way, what does BTW stand for?
It is better to be tried by 12, than carried by 6.