+10 for the Made in Japan Eneloop rechargables. I usually buy mine from dell when they go on sale.
Ditto. I meant to mention that in my previous post. Also, if you're a Costco member, they frequently have them on sale with a charger. (Unfortunately the bundled charger has the "must charge in pairs" mis-feature, but they're still a good deal on some of the best NiMH cells around.)
MAKE SURE YOU PAY ATTENTION TO VOLTAGE on the rechargables. I got a Rayovac kit (2-AA & 2-AAA with charger) and they're 1.2V. I stuck the AAAs in my remote and it wouldn't work. I was stumped for a while until I inserted some "regular" AAA's and it worked fine. The "regular" AAA's are 1.5V. I haven't tested the rechargables on a ton of things since then. Threw them in the junk drawer as a wasted purchase.
The 1.2V is due to the NiMH chemistry used in pretty much all consumer rechargeables; there's really no getting around it. Maybe someone will eventually come up with another rechargeable battery chemistry that is closer to 1.5V.
Nearly all devices that nominally require 1.5V batteries will work fine with 1.2V. This is because normal (non-rechargeable) 1.5V batteries slowly drop in voltage over their service life, so most battery powered electronic devices are designed to work acceptably down to around 1V or so. There are occasional exceptions; I've got a cheap point-and-shoot camera that complains about the battery being low when using NiMH rechargeables, but other than the low battery warning randomly coming on the camera still works fine. NiMH also maintain a very constant 1.2V until they are completely discharged, and have lower internal resistance than most non-rechargeable batteries; this can actually give them an advantage in some applications (especially devices where high current may be required).
Eneloops it is, then. Didn't realize that self-discharging batteries was a "feature" - totally annoyed to find dead controllers in the past, so I quit using rechargeables in them.
It was a general shortcoming of NiMH tech until Sanyo figured out how to deal with it. They've been doing the low self-discharge NiMH batteries the longest, and have the most experience. All the rest are basically copying the Eneloop design.
As another testament to the reliability of the Eneloops, the set I bought when they first came out years ago is still in service.
If they can somehow figure out how to do rechargeable lithium ions in a AA, AAA format @ 1.5V and include a controller circuit inside the battery all for a decent price then that would be the best... but, yeah :/ The only AA sized lithiums available are 3.6V cells that are meant to be assembled into a battery pack with a controller circuit.
Yup, the chemistry of lithium ion is all wrong for 1.5V. There would have to be some electronics (switching regulator) in each cell to down-convert to 1.5V. The tech to do this exists, but the extra electronics would add to the cost of an already somewhat pricey cell. Best way to keep cost down would probably be to have most of the intelligence in the charger, and just put a simple buck regulator in each individual cell. Unfortunately you will lose some efficiency with a regulator, but energy density of lithium ion is high enough that you should still come out ahead (and you'd be able to have "true" 1.5V rechargeables).