Will the Canon 5D IV take the Canon 5D III Battery Grip BG E11?
Sadly, the answer appears to be, NO! The batteries from my old Canon Mark III and my Mark II work just fine but it appears that once again, Canon has changed the grip just enough that the grip will not fully seat into the camera. I can’t help but think that Canon could have easily made this work given the grip’s fit is so close and the pin configuration appears to be the same. But alas, we are forced to buy yet another grip. If you want the new grip, you’ll be forking out about $349 currently on Amazon.
Fortunately, the pile of LP-E6 batteries appear to work fine. The Canon 5D IV comes with a battery labeled LP-E6N. I have not tried that battery in the Canon 5D Mark III but it appears to be a 7.2V 1865 mAh(Li-ion) vs. the LP-E6 which was an 1800 mAh(Li-ion). So, the new battery should have a small increase in life when compared against the older version however the 5D IV eats a little more juice, especially with Wi-fi or GPS enabled.