But wouldn't you think that's important to have an accurate reading of your battery? It's ridiculous to play a guessing game on your battery capacity.
Sure, if it's giving funny readings, like telling you you've got half an hour runtime on a full battery. That's when calibration might help.
But eg my 2009 13" MBP is just off the charger, it's at near full brightness and I've got Mail, Safari open. It says 5:00 hours remaining which is pretty much what it always says. So it doesn't need calibration. My old MB is four years old now, it's never been calibrated because it always says about the right hours remaining.
Istat tells me my MBP battery has 94% health, which is the MBP's estimate of how "big" the battery is. That's the key number. If that starts wandering wildly, say 20%, it needs calibration.
But the point I was trying to make to the OP is that that health naturally wanders about a bit, say by 10% because
-the capacity of your battery
does change with temperature etc, and
-the Mac's estimate isn't that accurate
I am damn sure that if I calibrated my MBP battery I'd get a different health, say 97%. But which is the right answer - 94%? 97%? Somewhere in between? It depends on the battery's circumstances at the time, particularly (I guess) its temperature and what else the Mac was doing while it was charging up.
If your health estimate is within say 90-110% IMHO there's no point calibrating. Because the on screen time display is only a guide, it's not super accurate (ie I can be damn sure my MBP won't last
exactly 5:00 hours).
The health number wanders about from charge to charge so calibration will give you a different answer each time, but not necessarily more accurate. It won't make the on screen display
much more accurate. Calibration will just put a needless load cycle on your battery.
Of course it's up to you. But calibration won't make your battery store any more or less juice, it just helps your Mac better estimate how much juice is in it. And usually your Mac's estimate is pretty good without calibration. By all means calibrate, but it seems like a right old hassle to me for no significant benefit.
