> Nikon MH-22 ... it only charges one at time even though it is a dual charger it makes no sence.
Well, I have one of these, and I think it works just fine. I might run two batteries down in a long day at a race - meaning two different cameras. For me, that means I shot about 2000 frames on one camera and probably 800 on the other one. I get back to the hotel, plop the batteries into the MH-22, put a fresh set in the cameras, and hit the sack. In the morning, they're both charged, and they go into the bag. It certainly seems to make a certain amount of sense. I don't really care that the batteries got charged sequentially while I was inspecting the back of my eyelids...
> i am not one to use my camera that often, maybe 3 times a year
Given that statement, I'm not at all certain that you need three batteries at all, and probably even two is overkill. Even given that your camera and battery don't have the capacity of the EN-EL4a's that go in the MH-22, I'd be pretty surprised if you can't get 500 frames in a charge. Do you really need to go further than that?
_____ Brian... a bicoastal Nikonian and Team Member
My gallery is online. Comments and critique welcomed any time!