Rechargeable Batteries
Dan from Wenonah, N.J., called asking which type of rechargeable battery needs to be charged completely before being used.
Only NiCad, nickel cadmium, batteries suffer from the memory effect, and there's some evidence that even that's a myth. According to some, it's best to drain them all the way before recharging and to fully charge them each time.
I use NiMH (nickel metal hydride) rechargables in place of alkaline batteries for most things and have had great results. NiMH batteries aren't subject to any memory effects and they're especially good in digital cameras and MP3 players. Don't use them in any device that sits on the shelf for a long time, like flashlights, because they "leak" and will drain down to zero power within a few weeks.
Most devices, such as the iPod, that don't have removable batteries use LiON (lithium ion) technology, as do nearly all notebook computers. LiON batteries are not subject to the memory effect either, but like all rechargeables, they can only be recharged a limited number of times before they'll fail. Most LiON batteries die after several thousand charges, typically a couple of years of use. LiON batteries can explode if overcharged, but they all come with circuitry that prevents that.
