MacBook Pro Battery - When should I replace my battery.

Check your Full Charge Amperage under Battery in System Profiler. If its under 80% of the original capacity of the battery, get it replaced. ( contact Apple or buy a new one )

This is what my computer says for the battery:
Does this help?

Model Information:
Serial Number: Sony-ASMB012-3503-28af
Manufacturer: Sony
Device name: ASMB012
Pack Lot Code: 0003
PCB Lot Code: 0000
Firmware Version: 102a
Hardware Revision: 0400
Cell Revision: 0303
Charge Information:
Charge remaining (mAh): 1878
Fully charged: Yes
Charging: No
Full charge capacity (mAh): 1878
Health Information:
Cycle count: 112
Condition: Check battery
Battery Installed: Yes
Amperage (mA): 0
Voltage (mV): 12462

Looks like you have a very bad battery.

Depending on your actual model and battery, you should have in excess of 5,000 mAh Full Charge Capacity. Yours is 1,800 - very weak. Mine died at 3,400.

You only have 112 cycles, a reasonable life is certainly over 200, and maybe 300.

I think you have a good case for a replacement - best bet to get this achieved is to go to a Genius bar in an Apple store and smile nicely!

Thanks for the info!

I think I may have a bad battery. I have had it a little over 2 years now. I do have AppleCare and here are the stats for my battery:

Battery Installed: Yes
First low level warning: No
Full Charge Capacity (mAh): 2292
Remaining Capacity (mAh): 2148
Amperage (mA): 591
Voltage (mV): 12568
Cycle Count: 301

It seems that 300 is the magic number and I am going to be frustrated if I am over the limit by 1 or 2 cycles. Would having AppleCare make a difference in getting the battery replaced even though it may have just been through it's normal "life time"?

Unfortunately, once you get to around 300 cycles, it's tough to make any kind of a case for a free replacement, whether or not you have Applecare, and especially after 2 years. You're at the point where your battery's performance would be expected to decline as the battery wears out. Sometimes people get lucky and their batteries last longer, but it's not something you can count on. I just don't think that Apple would be inclined to consider a battery that lasted for two years and 300 cycles to be defective.

Does anyone know if having your computer plugged in most of the time diminishes the battery's ability to hold a charge?

My battery/ computer is a year old. It has gone through only 40 cycles. I have been having trouble with the computer shutting off randomly after being unplugged for about 45 minutes to an hour.

I called apple, they said to calibrate the battery, which I can't do since I can't deplete the battery. The computer shuts off after 45 minutes then won't turn on unless I plug it in.

Earlier today my battery said it had 5330 capacity. Now all of a sudden it says 2259. I'm going to have to have a chat with apple again. I was just wondering if having it plugged in frequently could be the culprit. I do a lot of highly draining activities(video editing, watching dvd's, web video) so I am often tethered.