Non-OEM grips can damage cameras and/or batteries and that MAY be what is going on here. I have no clue as to your procedures for charging and using batteries, what you normally shoot, what lenses you use, age of the batteries, etc.. Can't advise you further. I ONLY use OEM grips and OEM batteries, and, over many years have had only one battery that I thought died too soon. I consider batteries to be an operating expense and that they will need replacing from time to time. I appreciate Nikon's current system of letting you know when your battery is nearing end-of-life and have really not had any issues that caused me any concern. I shoot with the D5, D810 and D500 and use the same battery in each of them via the grip. For my work, I consider the EN-EL15 unacceptable as I shoot sports action. All my bodies use the EN-EL18 (or 18A and now 18B). Best of luck.