Friends of ours purchased a Promaster branded battery grip for the Nikon D7100 I sold them a few weeks ago. The kit included 2 Promaster batteries. After charging the batteries and attaching the grip to the camera powered on and worked fine for two weeks before the grip installation using the Nikon battery supplied with the camera. After attaching the grip it worked fine for a short period of time, a few days and maybe 150 - 200 pictures and then the D7100 went dead. I now have the grip, batteries and the D7100 and was asked to try the combo on my newly purchased D7200 but I'm afraid to. The D7100 doesn't power up with my genuine Nikon battery or the batteries supplied with the grip. Just curious if 3rd party batteries or the electronics in the grip shorted something out? I'm feeling bad for our friends because I was the original owner of the D7100. I used the money from the sale to purchase a D7200. I only used the D7100 with genuine Nikon batteries and I didn't own or use a grip with it. The grip and batteries were purchased locally. What would you do? Who would you send it to for repair? I'm afraid Nikon won't touch it because it happened with 3rd party gear. My wife is afraid this incident will hurt our relationship with friends if I don't do something about it although I feel that I'm not at fault. So far the only good thing is the store will refund the purchase for the grip and batteries kit.