My experience suggests that if they are batteries for a specific device like a 1Ds-MkIII, you are probably fine. My camera bag is a carry-on containing 2 Canon 1-series bodies, 7 lenses, 4 flash units, and 4 total batteries, and TSA has never asked whether the camera batteries were lithium or NiMH. I've also had a bottle of Eclipse sensor cleaning fluid (pure methanol, highly flammable, and definitely not permitted) in the bag for 5 or 6 years and have been through TSA security at least 15 times and nobody has noticed it yet. When they look in the bag (and they usually do), the screener's reaction is usually along the lines of "whoa, that's a lot of camera s**t", they occasionally look through a lens or viewfinder, and sometimes they swipe the bag for explosive residue. I've never had anyone ask about batteries; ones for the 1Ds-MkII would probably be under the gram limit anyway, if laptop batteries are OK; laptops draw far more power than a DSLR.