I will try and make this as clear as possible because it is hard even for me to see the pattern of how charging works for this device. So far, these are what i have:

cables:
OEM cable,
6-ft cable,
1-ft cable,

chargers:
OEM wall charger,
iPad wall charger,
portable battery charger(with both .5Ah and 1Ah sockets),
USB car charger.

so far these are the combination that works:

OEM wall charger + any of the cables I have available
any charger + 1ft cable.
Macbook air + any of the cables I have available

This means that my portable battery charger and car charger only works if I use the 1 ft cable.

I understand that chargers have diff amperage and that might be the reason why some works and some doesn't. I'm wondering what the diff in the cables that I have though. How come some of them work and some don't? And why is my 1ft cable even better than the OEM that my N7 came with? I've had Apple devices for the longest time and they are all interchangeable. I thought micro USB would be the same. I was mistaken. Can someone here shed some light on this matter?