*I know the difference between the terms "battery" & "cell." I use the term "battery" because that is the (improperly used) term that the average person is familiar with.
I am an avid user of AA & AAA rechargeable NMh batteries so I'm going to share simple tips (that nobody else will tell you) that will maximize the overall lifespan (capacity & number of recharges) of rechargeable batteries. This applies more to the individual cell NMh (Nickel-Metal Hydride) type than it does to battery packs (you'll see why in a moment.)
90%+ of chargers charge at a rate (current) that is too rapid and destroys the lifespan of the battery through excessive heat generated while charging. The charger companies do this on purpose because they are usually the same companies that aim sell you more rechargeable batteries. There are some chargers (made by companies you probably wouldn't recognize) that will charge batteries at a slower rate (current) that respects the battery's requirement for maximum life... but most people don't own this kind of charger.
TIP #1 - Never buy or use any charger (or charging mode) that describes its self as "fast" or "quick." These are even more damaging than the standard charger that already charges too fast. I have seen these fast chargers virtually destroy the capacity and lifespan in only ONE CHARGE CYCLE... reducing the capacity by half of what a properly charged battery would have had!!! And there is no coming back from this kind of damage. It is permanent.
TIP #2 - Here's the big one... USE A FAN TO COOL BATTERIES DURING CHARGING!!! Yes it's that simple. A small desk fan works great for this purpose, but use whatever you have. You're going for maximum air circulation here... SO PLACE THE FAN VERY CLOSE. Some chargers have a lid... that must be left open. If the charger will not operate with the lid open, you may be screwed... unless you can figure out another way to activate the lid switch.
