Charger Question

[LCieParagon]

Hello I have a question that may seem dumb.

I charge my calculator near where I charge my phone, and at night it's hard to tell the difference which cord is which.

I've noticed something strange though. My phone charger will charge my calculator quite fine, but the calculator charger will not charge my phone. I've looked up micro USB A and B information, but the two cords look absolutely identical. I cannot spot a difference with either male end of the device. Both cords fit all devices fine and there is no jamming or forcing of cables.

Can someone point me in the right direction as to why this is so?