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Whether the end product is a video camera or an electric car, much of its performance relies on the battery. Different battery chemistries work well for different uses. Lithium-ion cells, for example, are good for laptop computers and other applications where there is a low drain rate, but not practical for cordless tools, which need a lot of current at one time. In the world of cordless tool manufacturers, the present debate is between two cell chemistries that are essentially identical in voltage output (1.2 volts): NiCd (nickel-cadmium) and NiMH (nickel-metal-hydride.)
Many manufacturers are staying with NiCd because they feel it's the best power source in two key areas: better cycle lifetime (that is, the number of charges and discharges possible over the lifetime of the battery); 2) better performance at extreme temperatures. Other manufacturers (primarily Makita and Panasonic) are opting for NiMH however because it's more environmentally friendly (no cadmium), has a longer running time with the same size battery, and is less prone to memory. Not to say that these batteries are the only game in town. At least two manufacturers—85-year-old Black & Decker and new player Igo—are bringing out tools powered by alkaline batteries for those who want featherweight tools plus freedom from plugs but don't feel the need for maximum punch. |
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An old-house owner doesn't have to be a vintage human being to remember when a "battery tool" packed more novelty than practicality. The first cordless drill didn't appear until the Kennedy Administration and, for a long time after, getting a few dozen 1/4" holes out of a charge was a lot to ask. A battery's recharge time was nearly equal to its owner's sleep cycle. The industry has come a long way. Power and run time have increased steadily over the years, while creative design has reduced tool weight and improved "usability." The latest cornucopia of quality cordless tools includes several that, until now, were impossible to power without a cord. In fact, manufacturers offer such an array of new tools sizes, voltages, and power ratings—on top of earlier-generation tools that still sell well—that anyone working on a house can get confused about what all the numbers mean in terms of actually getting things done. If you're in the market for a cordless tool, here's a breakdown of the latest developments you'll encounter in this broad and growing industry as you survey your choices.
Vive la Difference The growth of the cordless tool market, as well as its technology, is even spawning some tools with no strict precedent in the corded world. What at first glance seems to be an unending proliferation of T-handled battery drills is, on closer inspection, the appearance of a related but different breed of tool: the impact driver. Popular for many years outside the United States (particularly in Japan) and rapidly adopted by American construction trades, cordless impact drivers are now coming on strong with consumers for all kinds of applications. Sharing some mechanical principles, but little else, with hammer drills and air-powered impact wrenches, impact drivers look like a svelte version of a cordless drill without the traditional three-jaw chuck or internal clutch. Unlike hammer drills, impact drivers help drive screws, lag bolts, and similar fasteners by adding rotational impact—that is, striking the fastener in the direction of turn, rather than into the surface—when the fastener reaches a certain torque (turning power) resistance. This percussive action makes the work easier to perform (you don't have to strenuously grip or brace the tool), and it helps seat the fastener head properly into the surface. Impact drivers quickly became the tool of choice for commercial installation work, such as driving heavy lag bolts for anchoring garage doors, but now are equally popular for anchoring decking and molded plasterwork. Trying to analyze why rechargeable-battery tools are so popular has, interestingly, inspired at least one manufacturer to explore new directions in corded tools. While freedom from electrical outlets is certainly key, Craftsman believes that another cordless appeal has been the clutch, which lets users adjust the amount of torque—especially important for driving screws into soft material. As a result they've introduced some corded drills that feature clutches and dual-range gearboxes, but which are compact and lightweight to an extent difficult to achieve with cordless tools.
New Package Deals Biggest may be best for some specialized construction professionals, who will need the newer 24-volt power tools with their greater torque and rpm capacity for, say, daily fence building. However, general-purpose users like old-house restorers, who are now both more discriminating and more realistic about their needs, have helped establish 18 volts as an all-around comfortable balance between power and comfort. In fact many users, especially women, find 9.6-volt tools among the easiest to hold. Ray Holbrook, portable power tools buyer for Craftsman, notes that about 32 percent of the shoppers in tool departments are women. "We do a lot of research with end users to find out what they're looking for. Power is their number one concern, but they also mention ergonomics—good weight and balance to make the tool easier to hold and use." Steve Cole, product manager for Bosch, says this improved ratio of greater power and lighter weight could go on indefinitely, in terms of currently available technology, but not without pushing tool prices beyond acceptability to potential buyers. What today's consumer seems to be lapping up is the combo kit, says Christine Potter, production manager for DeWalt. The most common package includes a drill, a reciprocating saw or circular saw, and a flashlight. Cole says Bosch's new products will stress "commonality"—not only will all the tools in a kit be compatible with one charger, but buyers can power up a new drill/driver with the charger from a previously owned model. "We want to keep users in the Bosch family," he explains.
Assault on Batteries How does a manufacturer squeeze more work out of a battery? In simple terms, by innovations in the chemistry or construction of the individual cells and sometimes their chargers. One approach is switching from nickel-cadmium (NiCd) chemistry to nickel-metal-hydride (NiMH) chemistry, an area of great debate. Another is enhancing construction and electronics. Makita, for example, by reengineering the individual NiMH cell package, has reduced its size from that of a common C cell to that of an AA battery. To the battery package they've added a heat sink and an electronic chip that "talks" to the charger. Heat—a byproduct of recharging—is the big killer of batteries, and manufacturers deal with the overheating issue in different ways. Some chargers contain a monitor that will say "yes" or "no" to recharging a too hot battery. Bosch's high-end computerized chargers use "fuzzy logic" to constantly monitor the battery temperature and adjust the current accordingly. DeWalt has a fan-cooled system to charge its 24-volt battery. Chargers for its lower-voltage batteries employ what the company calls a "tune-up mode" that keeps the batteries from developing memory effect (a phenomenon, produced by repeated shallow discharging, that reduces the effective capacity of the battery). Panasonic batteries are cooled while charging through the simple expedient of ventilation holes. Their self-diagnostic 45-minute charger shows the status of the charge through an array of LED lights. One thing all manufacturers seem to agree on is that with new technologies and cordless tool use expanding every year, they will "continue to monitor the market." If the future is anything like the recent past, that means there are even more efficient and job-specific cordless tools to come.
Suppliers
Black & Decker
Bosch
Craftsman/Sears
Dewalt
Fein
Hitachi
Igo
Makita
Milwaukee
Panasonic
Porter-Cable
Ryobi
Skil
Rechargeable Battery Recycling Center
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