Lithium-ion (li-ion) batteries work best when you partially empty them and then top them off. They don’t like to be emptied every time you use them. There is one exception: You should run your battery all the way down to empty about once a month. This ensures that the circuit that measures the battery capacity has an accurate idea of what “full” and “empty” are for your particular battery, since charge capacity decreases over time.
The standard advice for taking care of lithium-ion batteries comes from Apple and batteryuniversity.com.
When doing this kind of maintenance, most Apple laptop users simply use their laptop until Mac OS X automatically puts the computer into sleep mode. I’ve found that this doesn’t always leave the battery meter with an accurate reading of the battery capacity. However, I have found a way to empty and calibrate the battery more effectively.
I’ve noticed that my PowerBooks, when on battery power, run much longer when the iTunes visualizer is running full screen. When iTunes is in that mode, Mac OS X somehow seems to let iTunes bypass the usual automatic battery cutoff level, and forces sleep much later. To try this battery calibration method:
1. When you see a low-battery warning or when the battery level drops to around 5 minutes remaining, start iTunes.
2. Start playing your music library. It should be a long playlist (like the entire library) so that the playing time is definitely longer than the battery’s remaining time.
3. Make sure the Full Screen command is enabled under the Visualizer menu.
4. Choose Visualizer > Turn Visualizer On.
5. Wait.
You’ll probably find that iTunes keeps playing many minutes longer than the remaining time indicated by the battery meter. Eventually, Mac OS X will sleep the laptop. As a result of the longer runtime, the battery meter should indicate a longer life than it would have if you hadn’t extended the runtime with iTunes. Using CoconutBattery, I’ve confirmed that the number of milliAmp hours assumed by the Power Manager is higher after this procedure.
I don’t know why Apple keeps two different cutoff levels for sleep when on battery. It’s a mystery.
conrad chavez | blog 
I’ve just tried this, i can confirm it does indeed work and my battery went from 3200mah to 4800mah in coconut. This was on Snow Leopard
Thanks for this great tip(or bug :P)
with many people saying you need to calibrate smart lithium ion batteries to keep them working up to par, and nearly as many saying you dont need to do this, its difficult to know what advice to follow. I build my own computers, started in electronics when carbon zinc and lead sulfide batteries were the norm to power what are now called antique radios. and understand the nicad memory and need to zap them periodically. I also know lithium ion batts dont develop memory problems within the cells themselves, but believe the electronic watchdog circuitry built in to protect both them and the consumer, gest confused as to where full charge and full discharge are in the sacle of things, resulting in less than full charge and so less than full capacity. I have observed that laptop batteries tend to become almost useless when used with a computer thats always plugged in and will give only 10 min or so operation when I am away from a plugin and attempt to use them off the battery, on both my wifes $250 dell latitude and my sons $800 gateway, though ive rebuilt both computers twice and built from the bround up my desktop and the last 3 desktops ive owned, I admit I still dont completely understand the electronic circuitry inside the batteries or that for charging inside the laptops, though the chargers themselves are simple, and usually work fine, aside from the dc cord breaking inside the insulation often due to weak poor design and rough treatment while dragging the heavy smps around by the cord and fragile dc jack, that in the Dell resides on the mother board, necessitting no mean amount of skill to repair, or replacement of motherboard. both of which ive done on the dell, but the circuitry inside the battery and inside the laptop just for charging iremains largely a mystry to me. so each time i read information like this I try it and evaluate it myself. Until I make sense of the delima, thank you sincerely for adding more bulk to the knowledge base Im developing on lithium ion batteries. Someday I will understand them as well as I do say a tube radio, a computer or radar system. For a time I considered nbuilding a nicad battery for my wifes Dell, to iliminate the drudgery of learning how to caudle the combination of lithium ion battery with self defeating circuitry, along with selfdefeating circuitry inside the laptop and the need for the ac adapter to ptove to the computer it is worthy before the computer will allow the battery to simply charge, but then opted to learn what was wrong with each and repair redesign or replace them each time they fail. so far Ive replaced the mobo, replaced the dc jack in the second mobo replaced the ac adapter and the battery all for not charging and all on the same Dell D-600. And verified all the parts I replaced were indeed bad. The battery I replaced still has full charge on the cells but will not work and flashes every other light (1-3-5) green on the first press of the tst button on the batt, then flashes the last 4 (2,3,4, &5) green on second press, but will not power the laptop, nor will it accept a charge. Wish I understood why.
I’m actually thinking of retiring this blog post because it’s so old and things have changed a lot in the battery world. For example, Apple says that for their built-in batteries in the unibody models, user re-calibration is not necessary. I am guessing this is because of better battery monitoring circuitry.
This is still good for us PPC users out there still, who have Powerbooks doing critical tasks in an all-x86/ARM world. just like the people that still use SGI boxes running IRIX as workstations for _something_.