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