Hello, this is not necessarily a review but more of an explanation of how the Nikon D5100 battery grip works with aftermarket batteries. I've seen plenty of reviews of the battery grip itself and I've seen some explanations in both posts and videos on using aftermarket batteries but I still had some questions unanswered that now I understand now that I have the grip here. So I thought I'd explain a few things. Basically this is the Nikon 5100. This is the grip listed on Amazon as the newer NEW ER grip which is actually manufactured by this brand MEIKE. And the batteries I got for are just generic EN EL14 batteries. They claim that they're for video cameras because they don't officially work in the 5100 by themselves. The reason is because the camera when you first put a new battery in does a check to see if it's officially licensed Nikon or one of the licensed third party manufacturers if it's not, it doesn't work. The way around that with this grip, as you can see I have cameras working right now and I have two aftermarket batteries in. You have to first turn the camera on with the Nikon battery in it. Doesn't matter what side it is. I've seen some people say it has to be in the lab so people say it has to be in the right. It just has to be in it. Camera power is on with the Nikon battery. Now here's the trick. At any point that you take both batteries out the camera has to boot back up again with the Nikon battery. But as long as you swap batteries keeping at least one battery in it all times you can remove the Nikon battery. Let me explain a little bit here. So if I put in the aftermarket camera still works. Turn it off. If I take the Nikon out the camera still works. If I turn it off put the other aftermarket in. So now there's two aftermarket the camera still works. I can even take this left one back out. The camera still works. But at any point if I take them both out put them back in it will not boot without the Nikon battery in. You can see there a message there it says this battery cannot be used choose battery design for use in camera. At this point put the Nikon back and boot it. As long as you don't take it out but you add this battery to it now take it out and you're fine. You can have any combination of aftermarket as long as they don't both come out. At the point they both come out the Nikon one needs to come back in. And that's pretty much it. Hope you've enjoyed this. If you have any questions post any comments.