http://store.dji.com/product/inspire-1-remote-controller-cable-kit

Will the dongle in the link work on the phantom 3 battery and rc?  It lets you charge the rc off a flight battery.  The charging pins look identical to me, am I right? If the pins are the same, shouldnt it work?

Not natively, it won't...

I just tried it and it's the black plastic housing around the two pins that's keeping it from connecting to the battery. The pins look the same, but the P3 black plastic housing appears to be a little larger than the Inspire. (the P3 will fit on the Inspire loosely, but the Inspire won't fit on the P3) So when you try to connect the battery, the housing won't push the pins into the battery..... Likely by design because of the voltage differences.

If you're willing to cut  the plastic hood off the connector, it should work, BUT you're on your own, I can't guarantee it....  

As Terry has said, no it will not.
If you want to drain power from the battery if you are not going to fly for a while, it will auto discharge to storage level.
Or if you are trying to get some extra juice to the RC while in the field, the RC will last for several days.