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I used to use those Calumet ones for flash too and they were shit. Had to take dozens with me at a time. These are great and hold their charge for yonks.
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Back when I needed loads (flash slaves for use underground, lots of them, pretty much full tilt all the time) I would just pick up packs of the Lidl or aldi nimh, this is 2010-15 though, so no idea if the current ones are any good. Number of failures I had were incredibly small, mostly due to being left in a wet bag for weeks/months on end rather than actual failures I think.
Rechargeable AA batteries, Ive bought ones from Calumet before but they never seem to last. Any suggestions on decent ones that will be good for flashes