If you look inside the battery compartment in the cameras grip there is a coiled up spring top right in the photo , this the contact for the negative (-) terminal .
On the bottom left , near where your finger tips go when you hold the camera by the grip are two spring loaded pins . These are the contacts for the positive (+) terminal .
Notice there are two separate terminals , , both of these will/might need to be connected .
No idea why there are two separate contacts , but if you look at the MB-15 grip this also has three separate contacts , 1 x negative and 2 x positive .
Inside MB-15 grip , the battery holder in that just has two terminals at the end .
When you look in the battery chamber with it upright , the terminal on the left , nearest the shutter release button is the positive (+) terminal .
The contact on the right ( next to the thumb wheel ) is the negative (-) terminal .
The camera use either six batteries in the MB-15 grip or four in the one that goes in the camera bodies grip .
