no problem either way. living in expensive hawaii, i've brought boxes of batteries back from the mainland, and never had a question. about 1/2 the time i find the tsa (you've been inspected) note in my bags, but it doesn't seem to relate to what i'm packing as far as i can tell. now car batteries are another thing.
I've been told that a row of batteries can look a bit like ammunition. For that reason, it seems better to put them in cabin baggage, as screeners can then pull them out to look at them if they need to. Putting them in checked baggage might increase the risk that the bag is inspected so thoroughly that it misses the flight.
Of course, in the topsy-turvy world that's run by the TSA, this general advice might not hold true.
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I've never a problem either. The closest I've come is returning from Reno with a slew of loose quarters in the pocket of my briefcase - apparently, it came up as a random dark mass and the screener was very displeased that I hadn't put them through separately in a pouch or something.
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I've carried extra AA and AAA batteries in my carryon all over the world. The only place it was a problem was India, where all loose batteries were confiscated. They were to have been returned to me when I landed, but I didn't bother trying to get them.
I remember reading a post about Air India prohibiting spare batteries, but I can't imagine it being a problem domestically. I always carry extra rechargables for my camera, walkman, nc headsets, etc
Air India does this... but I believe it is a policy of all airlines flying out of India... at least it was for Mumbai a few years ago. I was travelling out on LH, and was required to give up spare batteries for my headsets. Several people behind me had to do the same.