Submitted by Eric Daniel
Ok, first off, this entry makes two assumptions: 1) you have access to some form of "residential" (110v-240v range) electrical power and 2) you have equipment that runs off of standard AA-AAA batteries (to the best of my knowledge there are no commercially available rechargeable A123 (a.k.a. "Surefire") batteries.) That being said, for those of you in the above two categories, this might be of interest.
Now days, just about every hand held device runs of batteries. In the "old" days, most military equipment ran off of specific, purpose built mil-spec batteries. NVGs for example, required one type, flashlights another, and commo gear yet a third. Now, everything pretty much runs off of stacks of AAs.
This is where a recharging system comes in handy. With the need for all those AA batteries, supply issues can come up, especially if you are in a less than well-established area of operations (again, if you haven't got access to power you're out of luck, but more often than not you'll get power before you get a brick of batteries.)
Early recharging systems were pretty straightforward; you put the batteries in and when the light turns green, they're charged. Unfortunately, unless you monitor the charger, this can lead to overcharging, which is bad for rechargeable batteries. In addition, rechargeable batteries also "bleed off" (self-discharge) at a higher rate than conventional, non-rechargeable batteries, so they have a much shorter "shelf life" than conventional batteries.
Fortunately, however, newer charging systems not only charge batteries faster, but monitor total charge and once they're full, the charger goes into a trickle charge mode, which keeps the batteries