What's an amp-hour? It's a way to rate the amount of energy a battery can store, kind of like knowing the size of your fuel tank. And, like driving a car, the harder you drive your cordless tools, the quicker you run down the battery, regardless of its amp-hour rating.

Most manufacturers supply 2.0ah batteries with their tools, however several companies market batteries with a variety of amp-hour ratings. I was curious what difference these ratings had on run time (the length of time you can run the tool on a freshly charged battery) and if a 2.6ah 9.6v battery could outperform a 2.0ah 12v battery, so I called up a Makita rep.

According to Vince Caito at Makita, the more amp hours the more run time, like having a larger fuel tank; however, there's a big but: Run time is always dependent on work load and demand. Because most of us demand a lot from our cordless tools, a 12v tool will always outperform a 9.6v, regardless of the amp-hour rating. And there's a drawback to higher amp-hour batteries: the higher the amp hours, the shorter the life cycle (total amount of charges per battery) because there's less fluid in the cells.

I also tested the batteries. I found that 2.6ah 12v batteries didn't drive as many screws as 2.0 ah 12v batteries -- same size screws, same 2x4 studs. So much for higher technology.