MacBook Pro - Battery behaving very strangely

Question

I have noticed there are already many threads on this, couldn't decide which one to post in so am starting a new one.
I have a MBP 2.33 C2D 17" from late 2006. Last year I experienced the 'expanding battery' problem, my battery totally warped out of shape and was not working properly. After a fair bit of trouble with Apple France (who basically said, too bad, buy a new one), I eventually was able to go above their heads and get Apple to send me a free replacement. This seemed fair seeing as I had bought my MBP within the timeframe of an official battery recall published on the Apple site. The new battery worked absolutely fine, and is now still less than a year old.
Recently though, it has started to behave very strangely. I hadn't made any connection that it could be to do with having upgraded to Snow Leopard, but in retrospect, after reading many of the threads here, it does seem likely that this is the case.. I recently did a big upgrade from Tiger to SL on this very machine, and it has been since then that I've had very erratic battery behaviour.
My symptoms are similar to many I've read here: The remaining battery time (when not connected to AC) will jump from say 3 hours down to 15 mins very suddenly. Then sometimes it will jump back up again. Sometimes my battery health condition will say 'replace now', other times 'replace soon' or other times 'normal'. Also, sometimes the machine will just go to sleep with no warning, even when it had estimated more than an hour of battery time left.. upon reconnection to AC, suddenly it says 0%.
I have always been careful to power cycle the battery properly, to let it run down regularly. Also since noticing this problem, the first thing I tried to do was recalibrate.. But I've tried twice now with no success. I let the machine run right down till it went to sleep, then left it on overnight, waiting for the power LED to stop flashing on the front of the machine.. But it wouldn't stop flashing even after being left off overnight. I have yet to try an SMC reset, will do that next.
I realize my battery is not brand new, nor is my computer. However, this was a replacement battery I received less than a year ago. I'll put the battery stats below, but I'm not sure I believe them because I've been checking what is says a lot recently and sometimes it even shows a full charge capacity of a negative number! Something strange is going on here. I obviously don't expect full performance from a battery nearly a year old, but what it's doing here seems to be more than just a case of a battery getting old, especially having seen that many other users are having a similar set of symptoms after going to Snow Leopard.
Model Information:
Manufacturer: SMP
Device name: ASMB014
Pack Lot Code: 0002
PCB Lot Code: 0000
Firmware Version: 0110
Hardware Revision: 0500
Cell Revision: 0102
Charge Information:
Charge remaining (mAh): 2453
Fully charged: Yes
Charging: No
Full charge capacity (mAh): 2453
Health Information:
Cycle count: 396
Condition: Replace Now
Battery Installed: Yes
Amperage (mA): 0
Voltage (mV): 12597
Any suggestions appreciated..
Cheers.

Answer 1

I just got off a call with Apple support. The tech agreed that my symptoms were not normal, even for a battery with a cycle count over 300 like mine.. especially with the fact that the system profiler is showing bizarre info that makes no sense such as a full charge of a negative number. He said that basically the only thing I can try is to do an archive and reinstall of Snow Leopard, since it seems that the operating system is possibly corrupted. I don't think it's anything to do with the physics of the battery, it is more likely that the OS is not interacting properly with the battery, thus giving false and conflicting readings and information.. He seemed quite certain that it can't be a problem with Snow Leopard itself, seeing as all of the laptops in the Apple Support office were on SL and did not have this problem. So in his opinion, a corrupted OS was the most likely explanation. In any case, he said that batteries are only covered by a 90 day guarantee, so if it turns out that after a reinstall, my problem doesn't go away, then I'll have no choice but to buy a new battery because they won't cover it... This doesn't seem very fair to me because if it turns out that the OS has nothing to do with it, then it must be a faulty battery, because this kind of behaviour is certainly not what I'd call acceptable for a battery of less than a year old.
Anyway, I'll perhaps try the archive and install process on the weekend and see what happens.