iphone keeps charging and discharging when plugged into my computer. It's not the cord and the phone charges perfectly when plugged into the wall

This fixed my problem. I've had this computer for 4 years now, and it continually does it, no matter the phone. I've gone through 4 iPhones so the problem is clearly the computer, not the phones.

Thanks so much for the help!

Bumping this thread. I am experiencing the same issue and have seen threads like this dating back to iPhone 4s without being resolved. Does anyone know of a workaround?

I, too, know it is not the chord, because it charged my old phone from my MacBook Air without an issue. The issue seems to be stemming from its attempts to sync with iTunes.

Maybe this is as simple as needing a new phone? I recently had mine replaced.

Bump.

My 2 year old iPhone 6 just started having this issue today. It just keeps vibrating and alternating between charging and not charging.

I'm not sure if it's the 2 different cables I've tried today—my home cable worked fine yesterday—or the phone hardware itself.

I've had this problem in the past, I've solved it by resetting SMC and NVRAM as follows:

Left side shift/control/option turn on power while holding keys for 10 seconds.

Command/Option/P/R hold while booting until 2nd tone.

Hope this fixes it.