After downsizing from full frame FX to Micro Four Thirds I also need to downsize my flashgun. For years, I have been using a trusty Metz CL-4 but it's too big/heavy to carry around with my delightfully small, light outfit. So I dusted off the Metz 54 MZ-4 I used on a rangefinder camera a few years ago and bought an SCA 3202 adapter for it. So far, so good. It is usefully powerful and works well with 4 AA alkalines, but there must be other options to power it, such as AA lithiums and rechargeables. I won't be using it often, but I want it to be ready to go when I need it, even if it is a few weeks since I last used it. My CL-4 is NiCad which is old technology and probably not an option any more. I'm guessing that my main options are: a) Use AA alkalines and carry a spare set, b) Use NiMH rechargeables and remember to recharge them regularly, plus carry a spare set of AA alkalines just in case I forget, or c) Use AA lithiums and no need for a spare set. The lithium option seems attractive because the darn things hold their charge for ever, don't ever seem to leak and will probably last me more than a year of use, so I will change them every January 1 in the knowledge that they will always work when I need them for a little fill flash. What is your choice of batteries for your flashgun, and what experience have you had?