So I have a D3000 and the stock 7.2v 1080Ah battery that came with it. I wanted extra batteries and got two non branded 7.4v 2000mAh Li-ion batteries. I charged them about two months ago and had them stored in the camera bag. Yesterday I went to Liberty State Park in NJ and used those batteries along with an aftermarket battery grip for the D3000. After only about 80 pictures I noticed that my batteries started to die out. So I have a few questions, (a) when using a battery grip do both batteries work at the same time or one at a time? , (b) is the voltage on the non branded batteries and issue?, (c) should I maybe look into other replacement batteries, if so any recommendations(looking to maybe get something more affordable than stock nikon)?, (d) did they die out so fast because they where stored too long without being used?
Another question, since I have 3 batteries and only have one charger, stock, any recommendations on a dual battery charger? Been looking all over the net and can't seem to find one that would work with the EN-EL9a batteries.
Thank you in advance for your answers and recommendations.