Battery capacity very low, despite careful use and maintenence

Question

Hello,
The current battery capacity of my MacBook Pro seems to be diminishing rather swiftly. I bought my Mac around 4 months ago, and have been using it for less than 3 months. I try to run Battery Calibration often (sometimes many times in a row, just because the situation allows for it), and I have never started charging it until it has went into standby due to low power. I tend to use it when running on battery, though I do occasionally keep the power-cord plugged in when fully charged.
The problem is, my overall battery life is down to 93% of the original, only with 63 loadcycles. That's not the worst part - it has recently been going down even quicker then before when 98% or so worried me.
I have kept a log of the life of my battery using CoconutBattery, it is as follows (in order from earliest to most recent):
98 % (5440 mAh) 2007-09-06
99 % (5464 mAh) 2007-09-09
98 % (5410 mAh) 2007-09-10
98 % (5440 mAh) 2007-09-12
98 % (5444 mAh) 2007-09-13
99 % (5450 mAh) 2007-09-13
99 % (5450 mAh) 2007-09-15
99 % (5463 mAh) 2007-09-15
98 % (5420 mAh) 2007-09-17
98 % (5429 mAh) 2007-09-19
98 % (5443 mAh) 2007-09-21
98 % (5392 mAh) 2007-09-21
97 % (5387 mAh) 2007-09-22
97 % (5360 mAh) 2007-09-26
97 % (5352 mAh) 2007-10-01
97 % (5387 mAh) 2007-10-04
100 % (5544 mAh) 2007-10-15
97 % (5339 mAh) 2007-10-16
96 % (5292 mAh) 2007-10-17
98 % (5437 mAh) 2007-10-19
95 % (5242 mAh) 2007-10-21
93 % (5143 mAh) 2007-10-23
Why are there so many jumps in percent, both up and down? How can I improve on my battery capacity? Can I anyhow make it increase back to the full 100%?
Is it better to keep it plugged-in or use the battery? Is the OK to charge it often?
Thank you for your time. I hope you can help!
Rudi

Answer 1

It doesn't say that on the apple site!
You're right, it doesn't. It in fact actually implies the opposite…
"Standard Maintenance
For proper maintenance of a lithium-based battery, it’s important to keep the electrons in it moving occasionally. Apple does not recommend leaving your portable plugged in all the time. An ideal use would be a commuter who uses her MacBook Pro on the train, then plugs it in at the office to charge. This keeps the battery juices flowing. If on the other hand, you use a desktop computer at work, and save a notebook for infrequent travel, Apple recommends charging and discharging its battery at least once per month."
http://www.apple.com/batteries/notebooks.html
Thing is, this text is aimed at those that rarely use their batteries as opposed to that those that do given that with regular battery use you're already doing the right thing.
Additionally, by regularly using your battery the function a calibration is actually relegated to a way of accurate reporting. Over time the cells degrade and the battery's circuitry as well as your MBP's SMC gets out of sync with this which results in incorrect battery run time figures. In the worst case this irregularity can result in your MBP shutting off without warning as it thinks it has more power than it really does. Calibration just lines this all back up again.
This does not mean you shouldn't calibrate but to do it only every now and then. I have an iCal to-do item to do it after 6 weeks from the last one although it can actually mean I don't do it for 8-10 weeks.
maybe change the battery - if so, will I still be able to purchase a new battery for my current SR model? Or should I buy one and keep it in stock now?
Assuming Apple changes the MBP battery on it's next revision you'll still be able to purchase new batteries for your MBP. While they don't make then indefinitely they won't leave us high and dry without a source of new batteries even after a line is not longer current.
Buying new batery is not recommended until you actually need it as Li based batteries degrade from the time they're made so the newer the stock the better.