Source: TOOLS OF THE TRADE Magazine
Publication date: July 1, 2002
By Mark Clement
About half the price of a cordless drill, recip saw, or circ saw is spent on batteries. Since replacing these batteries when they fizzle is expensive, many tool users often just get a new tool. New batteries for mobile phones and laptop computers are expensive, so extending their lives will pay off, too. Here are a few simple tricks to maximize battery life and run time.
Heat. Heat is a big battery killer. A battery heats up as you use the tool; that's normal. But it overheats, however, as you overuse the tool. You should back off a bit and your batteries -- along with the rest of the tool -- will last longer. That doesn't mean babysit your tools, it just means don't drill a 1-inch hole in 6-by with your 12-volt drill.
Another heat source comes from storage, especially for users in hot climates. Leaving your cordless tools and batteries baking in your truck box, on the deck, or on a roof all day will shorten the battery's over all useful life and diminish its ability to take a full charge. This is especially true for high-drain tools like recip saws or rotary hammers. Park in the shade if possible and take tools out of direct sunlight when possible.
Cold. The other end of the spectrum is freezing temperatures. NiMH's chemical reactions stop working at 14 degrees F; Nicad gums up at minus 22 degrees F.
Click here to read full article from Tools of the Trade