Conventional rechargeable batteries have numerous advantages that make them great to use for your portable electronics. But they also come with certain disadvantages. After purchase, rechargeable batteries have to be charged before they can be used. And once charged, rechargeable batteries lose the stored energy rather fast. The charging takes quite long and rapid chargers are expensive. Not only that, but continuous charging or frequent charge to "top off" the lost energy (without complete discharge) can destroy the battery.                                                                                        

All these negative attributes have one root-cause: self discharge. Self-discharge means that a charged battery slowly discharges itself without any equipment consuming any current. This is the reason for rechargeable batteries being sold in a discharged state. And this is the reason that keeping charged batteries for some time did not make any sense. When you needed them, the energy was gone. Sanyo eneloop batteries have an extremely low rate of self-discharge, which means they hold their stored energy for a very long time--charge your batteries once and put them in your kitchen drawer, and over a year from now you'll still be able to use them right away, without needing to charge them again.