[Film Prof]

In the last week, according to Coconut Battery, I went from 91% capacity to 53% capacity, with 163 load cycles.

Why would the battery take such a nose dive?

[Remxed]

have you tried calibrating your battery? Mac OS X 10.4 Help: Calibrating a MacBook or MacBook Pro battery

[Film Prof]

I haven't calibrated it recently. I'll give it a shot. Hopefully, it'll work. I don't see how it could have lost almost 40% of its capacity in less than a week.

[Simon]

And check this exchange program for MBP batteries.

[Film Prof]

Strange. I started to drain the battery last night, and all of a sudden, both Coconut Battery and iStat said I was at 89% capacity. When I'd finished calibrating the battery, I'm at 82% capacity on both.

But I'm no longer at 52%, so that's a plus.

[Simon]

Apple specifies that their notebook batteries are designed to retain 80% of their capacity within the first 300 cycles. The full charge capacity of a new MBP battery is roughly 5.4 Ah. You can check your battery's current capacity in System Profiler > Hardware > Power > Battery Information.

[Film Prof]

Now I'm at 86%, or 4734 mAh, per System Profiler, Coconut Battery, and iStat.

Somehow, I gained another 4% since yesterday. I'm not complaining, mind you; just confused.

[Simon]

The key is to not obsess with battery capacity. Only once it consistently and clearly falls short of the specified capacity you have an actual problem.