I have a white MacBook (MacBook4,1). I have owned and used it for over two years now (30 months, as coconutBattery would have me believe). coconutBattery and Battery Health Monitor both report that the capacity of the battery has gone down to 82% at 4123 mAH charge capacity (with design charge capacity being 5020 mAH). The load cycles (cycle count) is 376, and the battery is reported to be in normal condition.
Naturally, the battery drains faster now than it did, say, a year ago, or when it was brand spanking new. I don't mind that. That's understandable. What I do mind, however, and what perplexes me is that, after the battery is drained all the way down to around 30%, the MacBook shuts off in a split second. I can hear that familiar click sound from the hard-disk that comes when the power button is held down for a few seconds to forcefully shut down the system. It took me by surprise when I first experienced it. I thought that perhaps it went to sleep because the battery may have drained completely. But it never displayed any alert about low battery (the charge was still reported to be around 30% when the event happened). When I pressed the power button, the MacBook did a POST and started as it would after a cold shut-down.
It happened to me every time I had drained the battery down to around 30%. I would think that the electronics on board the battery controller would force the system to go into hibernate (suspend/sleep) mode, while making sure there is just enough charge left to keep the system memory alive somewhere. However, as far as I can tell, obviously, the controller has no reason to think the remaining charge (at 30%) on the battery is appallingly low to warrant any such operations. But, it is as if the battery suddenly abruptly completely shuts itself off, as if its connection gets severed off there in a second.
I am clearly out of any warranty. But, I would like to know what could be the problem here. The battery is dying, but at 82% capacity, I shouldn't think so. What do you people think?