When I got my Quark X AAČ, I also ordered an eight-pack of Eneloops for it and my three Wii Remotes. So far, though, I have kept cycling some old Varta 2700mAh NiMHs which may have seen some overcharging abuse in my old two-channel fast charger.
Almost every time I insert these in my Quark, it manages moonlight, low, medium and high just fine, but when I turn the head to turbo/max, it immediately steps down to medium level output. Switching back and forth between high and max, high consistently has a slightly higher output than max—for the first minute or so. After the light/batteries have "warmed up", max works as it should and is brighter than on high (although possibly still below the output I would see with the never abused Eneloops).
Can someone explain to me why this is happening? It's not really a big deal, and I don't fault the light for it, but it bothers me just enough to wonder what is causing this behaviour.