Imagine you can travel back and forth in time. You arrive at a job site 30 years in the past and tell your helper, "Grab the cordless rotary hammer and set up the laser level while I call the lumberyard on my cellphone." He'd probably ask what you'd been drinking.
Next, leap forward 30 years from now and ask your sidekick to roll out the extension cords. Chances are, you'd get the same reaction.
Plug-in tools are far from obsolete, but if all the hype we've been hearing is to be believed, the introduction of cordless tools powered by lithium-ion batteries may be the beginning of the end.
The Technology
Lithium ion is not inherently more powerful than its older, nickel-based competitors, nickel cadmium (nicad) and nickel metal hydride (NiMH); 18 volts is 18 volts regardless of battery design. But it can cram comparable amounts of potential energy into a package that weighs as much as 45 percent less.
Low-voltage lithium-ion batteries have fueled cameras, cellphones, and laptops for years. Only recently, however, have manufacturers figured out how to build high-voltage lithium-ion batteries that aren't prone to overheating. Once Milwaukee overcame that hurdle in 2005, most of the other major tool-makers rushed to follow suit.
The result has been a volatile market, to say the least. Among the tools I tested, one manufacturer's offerings are clearly not ready for prime time and another's won't be available for purchase until June, despite promises of an earlier rollout. Yet another maker chose to delete the circular saw from its combo kit just before this review went to print, though the saw will continue to be offered as a stand-alone tool. (Individual tool reviews start below.)
Overheating. In contrast to the nicad market, in which most manufacturers outsource their batteries from a single supplier (Panasonic), the lithium-ion revolution has spawned a variety of power packs from rival companies. For the most part, the differences between competing products — proprietary chemical formulations, internal battery protection circuits, air vents, and the like — simply represent various ways to prevent overheating. Even with those safeguards, most makers warn that you can destroy a battery if you deliberately overstress the tool — by trying to break a bit free from a hole by repeatedly squeezing the trigger, for instance.
More with less. A typical nicad battery is a collection of individual cells, each of which can produce about 1.2 volts. To make a 14.4-volt power pack, 12 cells are combined; add three more and you've got 18 volts. Since the only way to add power is to add cells, you can end up with a tool that's too heavy to do the job.
Lithium ion presents an attractive alternative because one cell — which weighs about the same as a nicad cell — can produce about 3.6 volts.
This ability to do more with less has inspired various manufacturers to head off in different directions. Some, such as Hitachi and Makita, have chosen to put 18-volt power into a nimble package comparable in size to a 12-volt nicad. Others, such as Bosch and DeWalt, have built 36-volt powerhouses that aren't much bulkier than 18-volt nicads.
Further advantages. If you leave a pack in the case for a few weeks, you'll appreciate the molasses-slow discharge rate of these new batteries. During a month of inactivity, a lithium ion's charge will decline by less than 2 percent. Compare that with a nicad, which will lose 20 percent of its charge during the same amount of time.
Also, whereas nicad performance tapers off as the battery runs low, lithium-ion power output remains consistently high almost to the end. In fact, I found that most of the tools didn't begin to slow down until moments before they died. To prevent surprises, several makers incorporate LED "fuel gauges" on their batteries. It's a good idea to check these before worming your way to the far end of a crawlspace or climbing to the top of a scaffold.
Impartial experts agree that lithium-ion batteries can endure many more recharging cycles than their nicad cousins. However, only time will tell whether you'll get two to three times as many charges with them, as most manufacturers claim (published predictions range from 1,200 to 2,000 cycles).
Not cheap. Street prices for these kits average $600; a comparable 18-volt nicad setup can be found for half that. There is another option: Hitachi, Metabo, and Milwaukee have designed their 18-volt lithium-ion batteries to be compatible with their 18-volt nicad tools, which gives users a way to upgrade with only a modest investment.
Circ saws excepted. The improved performance afforded by lithium ion means that more and more jobs that previously required a plug can be accomplished equally well with a cordless tool. If you were to purchase one of the higher-voltage combo kits (28 volts or higher), you might be able to do away with corded drills altogether, and you could probably leave your corded recip saw on the bottom of the job box.
But until the big tool companies discontinue their AC-powered circular saws, no one can argue that plug-ins are passé. In the cordless market, the circular saw remains the elusive Holy Grail; a full-time cutter for a busy framing crew still needs a plug.
Testing, Testing
I rounded up eight kits for this head-to-head contest. With two exceptions, each kit contained a circular saw, a reciprocating saw, a hammer drill, a work light, a charger with two batteries, and a carrying case.
One exception was Metabo; its kit featured a standard driver/drill that does not have a hammer function. The other exception was Bosch. Its combo kit was so new the manufacturer was not able to provide a work light in time to meet our publication deadline.
Before testing, I ran each battery through at least five cycles. I used only fully charged batteries for each of the measured tests. Tool testing is a subjective process, so I tried to minimize any biases of my own by making measurable, apples-to-apples comparisons whenever possible.
For the circular saws, I compared runtimes by counting the number of 2x4 crosscuts a saw could make before its power noticeably dropped off. I used the manufacturer-supplied blades, and I stopped and started the saws between each cut.
For the reciprocating saws, I followed the same 2x4 crosscut procedure to compare runtimes. I also tested the saws' power by timing them as they crosscut a 4x8 pressure-treated beam that had three 16d nails embedded in the blade's path. To keep feed pressure consistent, I hung a 12-pound weight from the front grip while holding onto the rear handle and squeezing the trigger. Although each kit came with recip blades, they weren't identical, so I installed a new Irwin blade in every tool.
Just as they do in the real world, the drills got a lot of work. I assessed their hammer capability by timing them while they bored a 1/2-inch hole 3 inches deep in concrete. I measured runtime by counting the number of holes they could drill through 2-by fir with a 1-inch self-feeding auger bit. And finally, I made subjective judgments about drill power and torque by boring with 1 1/2-inch spade bits, and by driving a succession of screw sizes.
In addition to running these standardized tests, I scored tool ergonomics, warranties, accessories, and just about anything else I could think of. A few tests intentionally mirrored one in an earlier 18-volt nicad review in JLC ("Cordless Tool Kits," 3/02); I wanted to see if the lithium-ion tools lived up to their promise of improved performance. The upshot? In the earlier JLC test, the average reciprocating saw crosscut 43 2x4s and the circular saw 124. But the new recip saws in the three 18-volt 3.0-amp-hour lithium-ion kits worked harder: They averaged 69 cuts and the circular saws 147. And the higher-voltage lithium-ion tools did even better.
Choosing the Right Kit
This is my favorite part of any tool review — where I tell other people what to do with their money. Of course, which kit you should buy — if any — depends on your particular circumstances and preferences.
If your present tools are getting the job done efficiently, don't buy anything. Wait to see what develops in the adolescent lithium-ion market. Prices will almost certainly come down as competition increases.
If you already own a Hitachi, Metabo, or Milwaukee 18-volt combo kit, consider replacing the batteries — especially if they're nearing the end of their useful lives — with compatible lithium-ion ones and a new charger.
If you're looking for an 18-volt level of performance in a new combo kit, I'd recommend the Milwaukee V18 group (for sheer power) or the collection from Makita (for superior ergonomic design but less power).
If cutting-edge performance is what you want, your best bet is the DeWalt or the Milwaukee V28. In terms of overall power, DeWalt wins hands-down. Besides packing a lot of juice, this kit fielded the highest-scoring circular saw and reciprocating saw. The work light was my favorite, too. But nobody would call the DeWalt tools nimble. That's why, if I were spending my own money, I would choose the Milwaukee V28 kit. Its tools are lighter and more ergonomic than DeWalt's but still plenty powerful; the V28 drill was the top performer in the test. I also really liked the battery fuel gauge.
Andy Beasley is a veteran woodworker in Monmouth, Ore.
