Random shutdowns since battey update!

Question

Hi.
I've had whine issues with my MBP 1st gen. which were fixed by a logic board replacement. I updated with the battery update recently and some bad bahaviour has happened since.
Namely I've had two random shutdowns which never happened before.
The first occasion I dismissed since I had it on high processor load and when the MBP shutdown I put it down to overheating.
Today the story was different.
The MBP was idling with some normal tasks. I unplugged the machine to cycle the battery as I do once a week or so. I calibrated formally last week after the battery update.
Approximately a minute after unplugging, the MBP activated both its fans to high speed. The processor load on both cores was under 10% so it was not due to processor load or rogue non responding process. I waited and the fans started to wind down from their high speed in the gradual way they normally do.
A minute or so later for no apparent reason the machine just shutdown all of a sudden.
The battery appears to be draining alot quicker. For example in the last ten minutes since I've been slowly typing this the battery % has gone from 90% to 75% with CPU loads under 10%.
I'm calibrating the battery again today but the sudden shutdowns really shake one's confidence in the machine in a deep way as you may all understand.

Answer 1

Did you Reset the PMU (power management unit)
between re-calibrations?
When you re-calibrate make sure you leave it more
than 5 hours draining without power, I generally aim
for 7 hours before re-connecting power.
It could be worth running the Hardware tests from
Install DVD1 (hold down d at boot) and see if it
reports any SNS (sensor) or MTR (motor) problems.
I calibrated formally ie. 6 hours after normal power related shutdown and wake from deep sleep mode.
I haven't reset the PMU but will try that later. I want to try and diagnose the problem as well as possible before trying lots of random things.
I have noticed that my battery is down to 90% of full capacity ie ~4900 mAh (5500 mAh is the nominal when new). I only have 122 cycles in the 14 months I have owned this. It's mostly on AC power but nevertheless it never occured prior to the battery update (Ockham's razor).