We'll spare you the rhetoric on standard, non-rechargeable batteries -- if you really need to hear our thoughts on those again, feel free to have a look here. We went into this test with a couple of primary goals. First, we wanted to ensure that each of these offerings could power a Nikon SB-600 for an extended period of time, given that many of the weaker rechargeables simply can't provide enough juice to these high-draw flashes. Second, we wanted to see which brand lasted the longest. We obviously haven't had these long enough to truly test out the longevity, but here's the published facts: PowerGenix says its cells can be recharged "hundreds of times," Energizer's new 2300mAh units can be recharged "up to 500 times" (250 more than the prior 2400mAh models), and Sanyo's Eneloop batteries (US version) are good for 1000 recharges.
So, we'll just get right down to it: all three brands managed to power our SB-600 flash, so it's safe to say that any of 'em will suit you just fine when it comes to handling high-draw wares. Now, we're sure you're eager to hear which brand tanked and which one lasted for eight months without having to revisit the charger; unfortunately for the drama queens in attendance, we won't be delivering any shockers here. We originally found that the PowerGenix cells would last around 300 to 400 shots in our flash, months in our wireless keyboard and 4x to 6x longer in our Wiimote than standard, non-rechargeable alternatives. Lo and behold, the options from both Sanyo and Energizer lined up almost exactly, with no significant delta to report between any of them. Boring, we know, but it's true. Both Energizer's batteries and the four Eneloops mustered around 350 flash shots (give or take a few in either direction based on weather, frequency of flashing and the alignment of the moon), and we're still waiting for our wireless keyboard to grow exhausted after three solid months of use.
So, if each of these align in terms of performance, what's the difference in cost? Excellent question, Watson. A four-pack of PowerGenix cells can be had right now for around $11, with a four-pack + charger bundle selling for $23. A four-pack of Energizer 2300mAh rechargeables is going for $12, with a similar charger + batteries bundle going for around $20. Sanyo's Eneloop batteries can be found in like configurations for $10 and $21, respectively. Suddenly, this feels a lot like trying to choose a WWAN card when every major US carrier charges the exact same rate per month. In reality, any of these three will serve you well, and if you're a heavy battery user, these kits will pay for themselves in just a month or two. We'd give Sanyo's alternatives the edge due to having twice the recharge longevity (reported, anyway) than the closest rival, but if you spot a deal on any of the three, click the buy button and never look back.