Cut the cord

Advancements in technology keep power tool makers expanding their cordless power tool lineups.

Just a few years ago, the only cordless tools you’d find on jobsites were cordless drills. Today, thanks to advancements in technology, professional users have many more types of tools they can use without having to drag around electrical cords. The list now includes power-hungry tools such as routers, light-duty nailers, reciprocating saws and impact drivers.

• DeWalt just introduced the first corded/cordless wet/dry utility vacuum. It’s designed to vacuum up to 200 pounds of drywall dust on one 18-volt charge or 100 gallons of water.

“The tool is designed for tradespeople who drive around in service vans, like plumbers and electricians,” says Pete Morris, director of cordless power tools for DeWalt. “They’re used to using cordless tools and want a portable vacuum that can fit in their truck.”

• DeWalt also recently introduced an 18-volt cut-off tool/grinder for metal cutting and concrete cutting applications.

Not to be outdone, other manufacturers recently announced a spate of new cordless tools.

• Milwaukee Electric Tool introduced a new 18-volt, 3/4-inch cordless impact wrench that features 325 foot pounds of torque, the highest rating of any cordless impact wrench available.

• Makita introduced a new 12-volt 3/8-inch cordless impact wrench that boasts the most compact design in its class, with a length of just 6 5/8 inches and weighing only 3.5 pounds.

What’s driving the surge in cordless tool production? Advancements in battery and motor technology.

“Technology is evolving so we can build tools that will do tougher jobs,” says Doug Bock, national sales manager at Panasonic. “Today’s tools offer higher voltages and greater battery capacity. And, we haven’t reached the limit.”

Less weight, more power
The goal of tool makers is to maximize the power of cordless tools without adding weight. One way that DeWalt managed to accomplish that goal was to introduce the use of high-powered magnets in its power tool motors.

“We pioneered the use of injection-bonded NIB magnets in the power tool market,” says Morris. NIB, or neodymium iron-boron magnets, are made from rare earth materials considered to be the strongest magnet materials available. The powerful, yet lightweight NIB magnets are commonly used in laptop computers, high-end DVD players and other electronic products.

“We’ve taken that technology and pioneered it in the power tool market. What you’re trying to do for a given output is minimize size and weight. Users always want power. In our XRP drill/drivers, we have an NIB motor platform. We wanted to have more power in our drills but didn’t want to increase the size,” Morris says.

Better batteries is another reason behind the surge in cordless tools development. Tool manufacturers strive to achieve a balance between battery power and battery capacity. Battery power refers to the amount of voltage required to power a tool. Like horsepower, the more voltage a battery generates, the greater power delivered to the tool. Battery capacity — measured in amp hours — refers to the amount of time a tool can operate on a single charge. In other words, if a tool touts a voltage/capacity rating of 18V/2.4Ah, it means the battery pack can power an 18-volt tool on a single charge for twice as long as one with a 1.2 amp-hour battery pack.

Power and capacity are equally important to professional users who need to know if a tool can deliver needed torque for the application and how much run time they can expect before they have to recharge the battery.

Users also need to know the cycle life of a battery pack, or how many times they can recharge the battery before it needs to be replaced. Cycle life on most professional cordless tool batteries is about 1,000 charges, although some manufacturers say their chargers can produce 2,000 charges before the battery pack is exhausted.

“With a cordless circular saw, for example, you could deliver a battery that gives you many more cuts per charge, but you might have to throw the battery away after three months. The idea is to deliver longest run time and make the battery last as long as possible,” says Morris.

“Higher amp-hour capacity packs that provide longer run time are more convenient for professional end-users to use on the job. Time is money and no one wants to stop in the middle of a job to get another battery pack at the truck,” says John Sara, cordless tool product manager for Milwaukee Electric Tool.

David Smith, executive vice president at Metabo Corporation, agrees that balancing power and run time is key to a successful cordless tool.

“Tools with exceptionally high rpm require a great deal of battery pack power just to turn the tool at a high rpm. When you have lower-capacity battery packs, you’re going to have a short run time with the tool before you have to recharge it,” Smith says.

The most common cordless power tools used by professional users today are 12 volt, 14.4 volt and 18 volt. Some manufacturers also offer 24-volt models, but because they typically weigh 8 pounds or more, they’re mostly found in two-handed tools, such as reciprocating saws and rotary hammers. Some manufacturers have tried to market 24-volt drills, but they failed to gain popularity because they were too heavy to operate with one hand.

Most manufacturers use nickel-cadmium (NiCd) batteries, but some, like Makita and Panasonic, use nickel-metal hydride (Ni-MH) batteries. Ni-MH cells typically offer longer run times than their Ni-Cd counterparts, but some tool makers report they have a shorter cycle life and higher cost.

“With Ni-MH, you can get over three amp-hours of capacity in the same physical size package as you could with 2.4 amp-hour nickel cadmium. You’re not adding any size or weight to the tool, but you’re getting more run time,” says Smith.

He says one disadvantage with Ni-MH batteries is that they offer fewer charges before the battery has to be replaced. Smith says a typical one-hour charger can charge a NiCd battery pack about 1,000 times, compared to between 600 and 700 charges to a Ni-MH battery pack.

Heat generated in the battery during the charging process breaks down the cell components and eventually kills the battery. Chargers that control battery temperature during the recharging cycle can extend the useful life of the battery pack.

In the past, chargers would turn off after the battery pack reached a certain temperature. More and more chargers now available use a microprocessor to monitor battery temperature and charging voltage. After fast charging, they automatically switch to a trickle mode. The battery pack can remain in the charger for long periods of time without building up excessive heat from overcharging.

Some manufacturers offer chargers that can charge a battery pack in 15 minutes or less with minimal heat buildup. They cost more than other chargers and can charge a single battery pack up to 3,000 times before the battery dies.

“From a cost/benefit standpoint, an end-user can come out far ahead over the life of the tool using that charger,” says Smith. “He can recharge the battery faster and can keep fewer spare batteries on hand.”

He adds that Metabo will soon introduce a 12-volt in-vehicle charger that will give 2,000 recharges, twice the amount available with its existing model.

Milwaukee Electric Tool recently introduced the industry’s first multi-bay charger designed to charge up to three battery packs at the same time. Sara says it provides faster charging solutions, enhances battery performance, reduces jobsite clutter and is the most durable and versatile charger in the industry.

Predicting the future
The future of portable power may be as close as your cell phone or laptop. The Ni-MH battery got its start in those products, and now cell phones have begun using lithium-ion battery technology. Some day, they may be used in cordless power tools, but for now, lithium-ion batteries are sensitive to overcharge and are better suited for constant, low-amp draw applications.

This article appeared in the September/October 2003 issue of Progressive Distributor. Copyright 2003.

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