iPhones w/ 4 AA batteries

[TMoore]

I've assembled several MB's recently, to be used for charging devices with 30 pin iPhone USB cables, and Micro USB cables, 2 AA, and 4 AA, shorted, and not shorted, ...and all perform as they should, EXCEPT...
when I use 4 nimh AA's to charge an iPhone, it will not charge. But with 2 AA's it will charge.
Do iPhones have protection that will prevent them from charging if the voltage is too high?

Using fully charged 2300 & 2700 mAh AA's:
Input has been between 5.37v and 5.47v.
Output, outer pins read 5.35v
Data- is 2.07v
Data+ is 2.08v

Any ideas?

[adafruit_support_bill]

It is possible that the iPhone is detecting the higher voltage and blocking it.

Input has been between 5.37v and 5.47v.

Sounds like these cells are fresh off the charger. What happens if the cells are discharged a bit? 4xAA should be closer to 4.8v for most of the discharge curve. In my experience (an older iPhone and other 5v loads) the load will quickly pull the output of the freshly charged NiMH cells down below 5v. But the newer phones may be more sensitive to overvoltage.

[TMoore]

Yes, fully charged.
I'll try discharging them a bit at a time, monitor the voltage, and try again.
Thank you.