Of course we know that the camera manufacturer's batteries are usually very reliable (Nikon, Canon), but extremely overpriced. When I purchased the D40, I bought two off brand batteries for about 10-15 bucks (for both). They have performed flawlessly--last much longer than the Nikon battery for 1/4 the price of a Nikon battery. When I purchased the D90, I did the same thing. I bought two off-brand batteries for under $20. I also got a 3rd party grip. If I put the Nikon and a 3rd party battery in the grip (at "full charge") the grip only recognizes the Nikon battery. I primarily used the 3rd party batteries in the grip since then. I've only thad the D90 for about 3 or 4 weeks, and the last time I charged the Nikon Battery, was well over a week ago. Well, the 3rd party batteries are essentially dead---they won't take a charge. I removed the grip, and checked each battery individually in the camera, and had the same results--less than 10% charge on a "fully charged" battery. I popped the Nikon battery in--which has been sitting in my bag for well over a week--and it still had a 100% charge. I haven't used my D40 in two weeks, but both off brand batteries are still at 90%+ charge. Not a big deal, I mean it's only a sawbuck, so I'm just gonna toss em and forget em, but I guess the point I'm trying to make is that I guess off brand batteries are just hit and miss. Any good off brand batteries anyone can suggest? My dead ones are "Premium Tech."