I obsessively researched batteries a year ago. Long story short, I recommend:
Battery: Sanyo Eneloops Charger: Maha C801D For those interested, here's the long story. Sanyo Eneloops are the defacto-standard in batteries now. I see them specifically recommended in different fields and explicitly stated as the battery used in numerous lighting tests. I use them almost exclusively. Charger is important, too. Don't skimp on that. BATTERIES There are 4 main types of rechargeable: (1) NiMH (Nickel-Metal Hydride) Highest capacity, but self-discharges over time. Loses 5-10% within first 24 hours, and 0.5-1% each day thereafter. I have a bunch of Energizer Rechargeables. Like Dale said, they're always dead when I go to use them. You basically have to charge them the night before you go caving. In camera flash stress test (yes, I know this is for headlights, but that's the test I was reading in my research and besides, James does photography, too), these average about 296 full-power flashes. Examples: Energizer Rechargeable, PowerEx, Sanyo 2700. (2) LD-NiMH (Low Discharge Nickel-Metal Hydride) These are a new variation of NiMH that don't self-discharge as rapidly. They hold 75-80% of their charge after a year. I've switched to these (Sanyo Eneloops) almost exclusively in both my headlights and camera equipment because even if I don't remember to or have time to charge them, they are ready to go. These average 235 flashes, 20% less than regular NiMH, but I'm happy to trade that for the long-term charge. Examples: Sanyo Eneloop, PowerEx Imedion. (3) Lithium Extremely long shelf life. Wide operating temperatures. Comparatively light-weight. Unfortunately, they're expensive and don't work well in camera flashes, so I don't use them. Average 218 flashes. Examples: Energizer Ultimate Lithium, Energizer Advanced Lithium. (4) NiCd (Nickel-Cadmium) Crap. Not even worth talking about. RECHARGER Don't overlook the importance of a quality charger. The lesser ones charge batteries in pairs and stop both as soon as one battery is fully charged, leaving the other only partially charged. The best charge each battery individually. They also have an optional "soft-charge", which helps extend your battery life by charging slower (i.e., 2 hours instead of the typical 1 hour), and they can recondition the batteries if they are no longer holding their charge well (doesn't work miracles, but helps). The one I highly recommend is the Maha C801D. It can charge 8 AA or AAA, each on their own circuit, plus has the optional soft-charge and reconditioning mentioned above. It's a bit expensive (~$65), but I currently have about 70 AA/AAA rechargeable batteries for my headlights and photography equipment, so it was worth the investment for me. I've read horror stories of failed recharging like Don's, but I've never experienced anything like that. I've recharged hundreds of batteries totaling well over 1000 recharges on various quality and crappy chargers and never had a problem. That's not to say that someday it won't happen to me, too, but so far I am quite pleased with the switch to rechargeables (well, pleased with the Sanyo Eneloop rechargeables--those Energizer Rechargeables drove me and apparently Dale crazy with their rapid self-discharge). One last note, all these rechargeable batteries degrade over time, so expect a usable life of about 3-5 years. Furthermore, manufacturing will affect battery performance and life, so it's best to keep batteries together in the same set as they were manufactured/purchased. A tip I picked up from another photographer is that as soon as I buy batteries, I label them with the year/month of purchase along with a 2 digit set/battery code, like 3A. That way, I can keep all the batteries of the same set together, and I know how old the batteries are so I can move old ones to less critical functions, like TV remotes. Yes, a bit obsessive, but when I haul my big ass GGG Pep bag loaded with camera equipment hours back into a cave then run around and setup equipment everywhere for a shot, the last thing I want is for my flash to fail because I accidentally mixed up some crappy old batteries with my new ones. Without my labels, they all look the same. :) --Bennett
