FYI: Runaway iPhone Battery

Yesterday afternoon my iPhone 4S battery began to experience unusually rapid discharge, 15% or more an hour on standby. I had never experienced this before, though I’d heard of it happening after an iOS update. That, however, was not my situation.



I fully charged it again, but the result was the same. Turned off some services. I did a couple hard resets. I even restored from a backup without any joy. I was stumped!

I checked the Apple support forums, and after sifting through dozens of unhelpful posts, I found one that seemed worth trying:
It suggested that I let the battery drain completely until the phone shut itself off. Then, charge it fully and continue to let it charge for several hours more.

Since this is similar to the procedure for calibrating a MacBook battery, it seemed reasonable to gave it a try. It seems to have done the job. I'm only down about 4% since 5am (more than 6 hours of light use).

It might be a good idea to repeat this occasionally as routine maintenance for your iPhone.