I'm not entirely convinced that the power management gets tired in these Clamshells - something that a PRAM reset can't cure.
I have a couple of clamshells, and they all have very unstable charging behaviors. They don't seem to recognize the capability of a battery - whether its new or old, charged or not.
But what can you expect from an antique laptop?
Frustrated at not being able to charge a battery that I know is still good, I came across an aftermarket dual charging device designed specifically for clamshell batteries. What's great about this thing is that it's $10!
What's really great is that it works!
It uses the Clamshell power supply (yo-yo plug), so you aren't paying for another charger that you really don't need.
You plug in a 'confused' battery, and this will give you a colored l.e.d. readout as to whether it likes the battery or not. So far, it's liked my batteries. The one that wasn't taking a charge thru my Clamshell took a full charge (4 or 5 hours) with the VST. After installing into my Clamshell, the power management is now accurately showing - get this - 4 1/2 hours on a full charge! My money is on that being accurate.
So this battery is back in service.
So I've now plugged in an oem battery that I'd written off sometime back. That one's charging while I write this....we'll see how it takes.
In summary:
Buy a VST charger for $10 at PowerbookMedic.com
I'm in no way affiliated with these guys, I'm posting this because this thing is worth its weight in gold (or should I say lithium ion).