Baby Your Battery

Baby Your Battery


Step 2: Use It or Lose It - or Replace It

If you store your LiIon battery with a full charge, it'll irreversibly lose about 20 percent of its charge capacity per year. If you aren't going to use your 'Book for a while, leave your battery partially charged (40 to 50 percent). Even then, LiIon cells lose capacity over time - but they lose capacity more slowly at cool (not freezing) temperatures. Think about that when you're choosing whether to store your old iBook in the basement or the attic.


Apple will sell you a new battery for any of its current 'Books ($129,, but the company no longer sells batteries for most of its older models. MadsonLine ( and BTI ( make replacements, and some retailers refurbish and resell used batteries (full disclosure: Kyle's company, PB FixIt, is one such retailer-Ed.). The main concern is age: It's best to buy a recently manufactured battery and not just a "new" battery that was made five years ago and has never been used.


Step 3: Gauge It


Battery capacity is expressed in milliamp-hours (mAh)-our 15-inch PowerBook started out with 4,400mAh, so its claimed 4.5-hour battery life tells us that the 'Book draws about 1,000mA per hour. You can determine your battery's remaining capacity with third-party utilities such as XBattery ($15, or iBatt ($15, on the Disc,, or you can use the Terminal (/Applications/Utilities). Type ioreg -l | grep Capacity and press Return. If you don't see a longish result, drag the Terminal window's lower-right corner to fill your screen. The first item, Capacity, is your battery's current capacity in milliamp-hours; the final item, AbsoluteMaxCapacity, lists the battery's original capacity.


For reasons unknown, the Terminal cuts off the results at the window's edge; start with a wide window.




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To view the whole output from ioreg, use

ioreg -l -w 0

This will prevent the truncation.

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