My iBook just shuts off when it is still partially charged. Help?

Question

Hello, I have an 14" iBook G4, and have been having problems lately with the computer shutting off (going dead, and not into sleep mode) after it has been running on battery power for awhile. It usually shuts off when the battery is at around 45-60 percent charge still left. It never shuts off when plugged in to the charger. Here are some specifics on the battery from the System Profiler:
Battery Information:
Battery Installed: Yes
First low level warning: No
Full Charge Capacity (mAh): 1545
Remaining Capacity (mAh): 1542
Amperage (mA): 0
Voltage (mV): 16543
Cycle Count: 225
I have been thinking about getting a new battery but I just replaced this one a year or two ago so I don't think it should be bad yet.
A few things that I think might be causing the problem might be that I upgraded this computer a while ago by putting in a 100 GB hard drive and putting in a Superdrive (it originally had a 40 GB HD and a Combo Drive). I also have an extra 512 MB of RAM installed. I also just recently upgraded to Mac OS 10.4.11. I had been running 10.4.6 for the longest time (mostly because I always though it was safer because sometimes when I had updated computers in the past they'd run into problems. Plus, I have software that I knew would run with OS 10.4.6 - plus the install discs).
Anyway, let me know what you guys think I should or could do to fix this problem. I'm on my computer all the time so I should respond quickly to your guys' (or girls') advice.
Thanks for any help you can give. Later

Answer 1

I looked into resetting the PMU (although I think I already tried that a week ago), I don't know if something specific is supposed to happen to let me know something was reset but everything functioned pretty much as normal.
I tried recalibrating the battery with minimal success, it went down to 31% then actually said 0% and died. I tried recalibrating twice and it doesn't go into sleep mode, it just dies. It'll go down to 0% and still not go into sleep mode. Now my battery reading says this(with the power cord unplugged):
Battery Information:
Battery Installed: Yes
First low level warning: No
Full Charge Capacity (mAh): 1315
Remaining Capacity (mAh): 1313
Amperage (mA): -778
Voltage (mV): 16178
Cycle Count: 225
I took continual readings of the Battery in the System Profiler and pasted them into a Word document when the computer was at 0% capacity and was still on but wouldn't go into sleep mode (it eventually just died). I can post some of those on here if you want.
I also tried that Coconut Battery program to let me know any new information about the Battery and it says nothing really new. It says the battery has a max capacity of 1315 mAh (although just couple of days ago it used to have around 1500mAh - read my first post above - I don't know if that means I've made progress or the battery is worse off then when I started) and also the Battery originally had 4400 mAh capacity (so now it's at about 29% of its original strength).
One thing did disturb me though is that the battery might not be recording the number of cycles correctly. Even though I've gone through at least a few charges in the last couple of days, it still says "225" and it should be higher. You'll even notice that it said "224" in the Battery Information in my first post. I've gone through at least a couple of complete discharges, I would think.
Anyway, I hope there are some more options on the table, but I'll see if I can keep re-calibrating it and it will finally work. I am starting to wonder if its the battery or the module inside it or some other problem. Anyway, thanks for the help.