Sanyo announced an improved version of their Sanyo Eneloop Low Self-Discharge Rechargeable Battery, 6 October 2009 . These are now avialable in Australia and I purchased two AA cells from Dick Smith Electronics in Canberra.
These are Nickel Metal Hydride (NiMH) rechargeable batteries, which can be charged in the same sort of charger as other NiMH batteries. The main advantage advantage is that the Eneloop batteries will keep a charge for years, while normal NiMH batteries only keep a charge for months. The new batteries are claimed to retain 85% of their charge after a year, whereas normal batteries would be 50% discharged. Also they can be recharged 1,500 times, 500 times more than conventional NiMH batteries.
This makes NiMH batteries practical for low current applications, such as running a clock, where they previously they would not be of use.
Amazon.com adversities the Eneloop in AAA Battery 4 Packs
and the AA batteries in 4 Packs and 8 Packs. There is also mains powered charger with 4 AA batteries and a USB Charger with 2 AA batteries.
There is also a very elaborate "Eneloop Power Pack Kit" 8 AA and 2 AAA Batteries, plus 4 C and 4 D Size adapters.
There is a detailed "Review: Testing Sanyo's Eneloop Low Self-Discharge Rechargeable Battery" avialable, along with a comparison of the new Eneloop against other brand of batteries "Review: Pre-Charged (Low Self-Discharge) Rechargeable Battery Comparison".
It will be interesting to see if the technology is also applicable to batteries for hybrid and electric cars. One of the worrying costs with electric cars is replacing the battery pack. If the battery can be made to last 50% longer, that will reduce the cost. Also a car which can keep the charge longer will be more practical.