Something to watch with D3 or any other DSLR battery is memory effect. Nikon can swear until the cows come home that their batteries don't have a "memory effect" but they do. It is best to let the batteries run down almost to the point of where the camera shuts off. If you have a spare battery this is actually a good thing to do. Granted, the D3 and D700 hundred are somewhat different when it comes to batteries but what I do with my D700 is I have a lithium ion battery in both the camera and battery pack. I have the thing set up to pull off the battery back first and then switch to the camera. Unfortunatly it will not do it automatically, a firmware fix I wish Nikon would implement. When that battery hits the level where the camera shuts off, I simply tell the camera to switch to the camera body and I go and recharge the battery from the battery pack. If I need more juice, I always have the alternate battery holder handy where I have 6 rechargeable alkalines in place. I also have a small DC to AC converter in the car all the time so I can actually plug the charger into the aux power outlet and charge camera batteries while I am driving. They are not very expensive and it may be a lifesaver if you run out of juice and need a way to recharge the batteries. I let the battery in the camera drain down to zero and then move to the battery pack again. This does two things; first it eliminates memory effect, and two, both batteries will receive the same number of charges. I keep a DC to AC converter in the car, which is a handy little doodad to have, so I can actually plug the battery charger into the aux power outlet and charge camera batteries while I am driving. It also works like a champ to run or charge a laptop too.