What kind of cordless drill or driver do you need?

We found the most comprehensive review of cordless drills and drivers at Consumer Reports, where nearly 70 models are put through objective tests of speed, power, run time and charging time. Ten of the tested cordless drills use lithium-ion batteries. Despite their higher price, expert reviews say lithium-ion cordless drills and drivers have such longer lives that they can be better investments in the long run. Lithium-ion cordless tools are also much better for the environment.

The lithium-ion cordless drills compared at Consumer Reports vary in voltage, while the more recent comparison tests at Popular Woodworking cover only powerful 18-volt cordless drills. Fine Homebuilding tests 12 lithium-ion cordless impact drivers in an even more recent review. A review at Tools of the Trade also tests lithium-ion cordless tools, including circular and reciprocating saws. A more recent review at the Journal of Light Construction compares eight cordless tool kits.

Lithium-ion batteries have also reinvigorated cordless tools at the lower extreme of size and power. Analyzing some 30 reviews, we find that the one cordless drill/driver that gets the most top rankings is also one of the smallest: the 10.8-volt Bosch PS20-2 Pocket Driver (*est. $100) . Experts say this 1.8-pound cordless drill can drive most screws without the need to drill a pilot hole. We found good comparison tests of this and other cordless screwdrivers at Popular Mechanics, GetWoodworking.com, Wood Magazine, Fine Woodworking and Wired magazine - plus single-product reviews in many other publications.

Reviews show that neither price nor voltage distinguishes the best performers; it really takes objective comparison tests and expert assessments of balance and ease of use. For example, despite their lifetime guarantee, reviews say that Ridgid cordless drills and impact drivers aren't the best performers. Among budget cordless drills, Ryobi and Craftsman outperform Black & Decker, Firestorm and Skil. Reviews recommend avoiding the Mansfield Dual Drill (*est. $120) that's promoted on TV infomercials altogether. For its price, reports say that you could get a cordless drill that performs much better.

What kind of cordless drill or driver do you need?

While it's tempting to get the biggest, most powerful cordless drill you can afford, expert reviews emphasize that for portable power tools, "less can be more." If you mainly need to hang pictures and shelves, assemble furniture and other light tasks, experts recommend a small, lightweight cordless screwdriver or "palm driver." At the other extreme, for construction projects like a deck or shed, experts recommend a cordless impact driver because it makes driving lots of screws so much easier. Here's a rundown of the various types and uses of cordless drills.

• Cordless drill/driver: Best for most homeowners. The most common type of cordless tool, these come with bit for both drilling holes and driving or removing screws. An adjustable clutch regulates the torque or twisting power applied to a screw. These are best for most homeowners who need both drill and screwdriver functions.

• Cordless hammerdrill/drivers for drilling in concrete or brick. These are more powerful but also heavier. They have a specially designed clutch that allows the drill bit to punch in and out while it's spinning. You can turn off the hammer action for general use.

• Cordless impact drivers for driving lots of screws. Impact drivers are different from hammerdrills. When an impact driver senses resistance, torque increases so the bit is less likely to slip out of the screw head than it would with a regular drill. While capable of drilling holes, they are mainly used for projects which require driving a large number of screws -- such as building a deck.

• Cordless screwdriver. Sometimes called "palm drivers," these are small, simple and lightweight tools, good for hanging shelves and pictures, or for assembling furniture.

If you're just drilling a lot of holes, a cordless drill is faster. But if you're drilling a pilot hole, then switching bits to drive a screw, a cordless impact driver is the faster and better tool, partly because it eliminates the need for a pilot hole.

There are several types of batteries used in cordless drills. Batteries are rated not only by voltage but also by amp-hours (ah), which greatly affect how long you can use the tool before recharging it. Lower amp-hours make the tool lighter and more compact as well as less expensive, but lessen the run time. The type of battery affects run time and price.

• NiCad batteries cost the least but are the least environmentally friendly -- that's because their manufacture releases cadmium. NiCad batteries require careful recycling to prevent contamination of soil and groundwater. They lose their charge in storage, and it can be tricky to maintain them properly through a lot of recharging cycles. Their one advantage is that they work well in very cold weather.

• NiMH batteries have a longer run time between charges and are considered more environmentally friendly. To work at full power in very cold weather they need a few minutes of recharging to warm them up.

• Lithium-ion batteries are smaller and lighter, so you get more power with less weight. A 28-volt lithium-ion cordless drill may weigh as little as a 18-volt NiCad drill. Lithium-ion batteries have a long run time, keep their charge for a very long time between uses and have a longer lifetime (more charging cycles) without any "memory effect." They also keep the tool running at full power up to the very last second of battery charge (using a "fuel gauge" to warn the user), and work well in cold weather.

 ... Continued (Best cordless drills overall)