I know the 3 volt lithum batteries like you use in the Surefire flashlights can have issues, even just you two different batteries, where one is just discharged more than the other. They sometimes spontanously combust.

Speaking of lithum camera batteries, I use the lithum AA batteries and while they are expensive, they are the best thing ever. They're light and they last FOREVER!! Hundreds more shots than any standard or rechargable battery and I just dug an old AA camera out of the drawer that I haven't looked at in at least 2 or 3 years and the thing still works with the original lithum batteries inside. Amazing stuff.

Anyway, I've gone completely away from rechargables and to the lithiums, but I keep them in plastic storage containers that are designed the store each battery seperately.