Service Battery warnings and warranty

[smchan]

The warranty on my mid-2009 MacBook Pro 13" expires in 2 days and my battery seems to be dying. I wish it would hurry.

This morning, I got a "Service Battery" warning with a "Check Battery" message in the Power section of About This Mac. Took my machine to the Genius Bar this evening and it passed the battery diagnostic with 81.1% health.

90 minutes later, I'm sitting outside at Barnes & Noble next to the Apple Store and I get another Service Battery warning. My full capacity charge is down to 3928 from the 4258 mah observed while at the Genius Bar. I carried the machine back to the Genius Bar but it was, unfortunately, closed. They made note of the warning and set an appointment for me to come back tomorrow.

Now (a few hours after my last Genius Bar visit), my charge capacity is 4210 - very slightly above the 80% capacity level needed for the tech to replace my battery.

Why is my machine so schizo? Any chance there's a relationship between the machine's temperature and reported charge capacity?

Thanks,
Sam

 

[GGJstudios]

Have you properly calibrated your battery? If not, your readings are likely inaccurate. This should answer most, if not all, of your battery questions: Apple Notebook Battery FAQ

 

[devilstrider]

buy apple care now

 

[smchan]

My battery only has 138 cycles but is roughly at 80% of original charging capacity. The Apple tech said remaining charge capacity should be much higher than 80% for 138 cycles. I last calibrated the battery over this past weekend with no significant change in reported capacities. 2 weeks ago, the remaining charge capacity was around 4400 mah, so it appears to be "hockey-sticking" downward.

A replacement battery is cheaper than AppleCare - but I'll likely buy AppleCare if my battery isn't far enough gone by tomorrow or Wednesday for Apple to replace it under warranty.

The interesting part is to see the reported remaining capacity jumping around on my machine. I suspect it's related to temperature and will do some experiments to be sure. Will shutdown (vs sleep) tonight so that it's completely cool when I check tomorrow.

Sam