Lithium-ion power creates a cordless niche

Various voltages plug into users’ needs, offering more power and less weight.

by Clair D. Urbain

It's been more than two years since lithium-ion (Li-ion) tool power came on the scene. Boasting more power, less weight and longer life, cordless power tool manufacturers are working the new chemistry into their tool lines. However, it has yet to supplant the popular nickel cadmium (Ni-Cd) powered tools that have dominated the cordless tool market for more than a decade.

“Li-ion solves the age-old problem of size and weight of cordless tools. The first cordless tools did not offer much power or run time and took a long time to charge. That improved over time with Ni-Cd advances, but with Li-ion technology, we have more power than corded tools, quick charging capability and longer run times. I think the whole market will transition to Li-ion within two years,” says Doug Bock, group manager for power tools at Panasonic.

A different animal
Li-ion cells are different from Ni-Cd cells in many ways. To capitalize on its power density (as much as three times as Ni-Cd), sophisticated electronics are needed, especially in high-draw power tools. Each manufacturer has its own approach, some putting microchips in the battery, some in the tool and/or charger.

“Li-ion cells are a better performing battery. It’s still a new technology for power tools,” says Rick Gray, director of marketing, product management at Milwaukee Electric Tool.

“Makita 18-volt Li-ion batteries weigh less and deliver more power than older battery technology such as Ni-Cd,” says Brad Wheeler, senior product manager for cordless tools at Makita. “Our batteries also help us deliver better product design because the Makita Li-ion battery doesn’t extend into the tool handle. The grip is designed around the human hand, not around the battery. In all, we’ve delivered 21 new tools in two years all powered by the Li-ion battery technology.”

The battery cells and tools are controlled by various types of microcircuitry that manage the power output, monitor and control charging and protect the unit from misuse. That still doesn’t mean Li-ion cells are invincible.

“The electronics in the Li-ion systems help the batteries last and run longer, and they are needed to manage charging and discharging. Ni-Cd doesn’t need that kind of technology for power, charging or discharging,” says Edwin Bender, group product manager for Bosch cordless tools.

“Over-discharging can cause Li-ion batteries not to recharge. If the cells overheat, the battery can become unstable,” says Bock.

“These are not cheap batteries. They are expensive to make, and a 3 amp-hour tool such as a drill driver will cost about $300. Some companies are going to 1.5 amp-hour batteries and tools to lower the cost,” Bock says.

However, Li-ion technology lasts much longer – some claim three times longer – than Ni-Cd cells. Imagine a power tool battery outlasting the power tool! In fact, Hitachi sources report it will offer tool-only versions so users can get more use out of its Li-ion batteries. Makita also offers tool-only models in its LXT line.

“Tools will wear out before the Li-ion battery packs,” says Bock. “We will see more tools sold without batteries included in the future.”

Various voltages
Cordless tools using Ni-Cd technology evolved from low-voltage, unreliable tools to heavy (in duty and weight) tools that weigh more than their corded cousins. From 5.6-volt screwdrivers to 24-volt circular saws and rotary hammers, the 18-volt platform came out as the users’ choice as the best trade-off between power and weight for Ni-Cd power.

When Milwaukee introduced its first Li-ion powered tools more than two years ago, it went to a 28-volt platform that offered nearly double the run time and significantly greater power while weighing about the same as an 18-volt tool. DeWalt soon followed, introducing its 36-volt tools.

“DeWalt went with the 36-volt platform first to expand the cordless tool market into an area where there were only corded tools. We wanted to go where we weren’t before,” says Tom Baldwin, DeWalt group product manager. This fall, DeWalt introduced 28-volt tools, as well as 18-volt batteries that fit its Ni-Cd-powered line of cordless tools.

18 volts is 18 volts
“There is a misconception in the industry that 18-volt Li-ion will deliver more power than an 18-volt Ni-Cd battery. Eighteen volts is 18-volts. “Li-ion technology only offers increased power and run time if you increase voltage, since power is determined by voltage and tool design. We believe end-users w ill migrate to the 28-volt platform as they need increased power and run time. With Ni-Cd cells, there is a restriction to increasing voltage because of the size and weight of the batteries, DeWalt's 28-volt Nano technology tools will be as light or lighter than 18-volt Ni-Cd tools with 1.75 to 2.5 times the run time of Ni-Cd,” says Baldwin.

Bosch has developed two Li-ion platforms: a lightweight 10.8-volt driver line and a 36-volt line that features two battery packs – the Slim Pack and the Fat Pack – that allows users to choose between run time or weight, reports Bender.

High and low voltage systems
“We have had Li-ion tools for 18 months, ranging from a 36-volt rotary hammer to 10.8-volt driving tools. We are at both ends of the market. Users want more power without gaining weight and the 10.8-volt tools have been a great success. They are small, compact, fit in the hand well and do the job they are asked to do. However, 36-volt adoption has been slower and we have had more success with our Slim Pack which weighs the same as a 14.4-volt Ni-Cd battery pack. The Fat Pack is the choice if you are working with the recip or circular saw; the Slim Pack is a good choice for one-handed tool jobs. We found that in our Litheon (Li-ion) combo kits, users prefer one Slim Pack and one Fat Pack, matching the battery to the job,” he says.

Panasonic’s Bock concurs. “You must look at the total tool weight. The 28- and 36-volt tools are heavier than 18-volt tools, which is about the top of what people want to work with as far as weight goes. The limit for one-handed tools is five lbs. A tool bigger than that must be designed as a two-handed tool,” he says.

Charging speed
Charging speed also makes a difference. Generally, Li-ion batteries charge faster than Ni-Cd cells, and the micro-circuits in the systems balance charging speed, heat and time. Typically, the 1.5 amp-hour batteries charge in as little as 30 minutes; 3.0 amp-hour batteries take under an hour to fully charge. Again, it’s up to the electronics and design to govern charging speed to protect the battery.

“Li-ion is a faster charging chemistry than Ni-Cd, and charging time varies based on the system used,” says Wheeler.

Price plays a role
Perhaps the greatest barrier to Li-ion’s success at this time is the price premium. “Ni-Cd is the majority of the market and will continue to be the better value. There is a 25 to 30 percent premium for Li-ion technology so Ni-Cd will continue to exist because it provides that value. The market will transition when Li-ion equals Ni-Cd in price,” says Bender.

DeWalt's Baldwin reports that the switch to Li-ion hasn’t been fast because users are still satisfied with Ni-Cd performance. “Contractors still don’t understand the power and weight advantage and what it can do for them. Over time, Li-ion battery price will find its sweet spot once users understand the benefits. That’s when they will convert,” he says.
“There is a general rule of thumb that cordless tools can be as much as twice the price of corded, but the high-end, high-powered Li-ion tools are running as much as three times the cost of a corded tool. They are still too heavy, too big and too expensive,” says Bock.

“You’ll see the technology continue to improve in tools over the coming years. The whole industry is moving toward Li-ion. There are economies of scale in price and, as green thinking grows, the ecological friendliness of Li-ion will attract more users. Ni-Cd use in power tools is on the decline. Eventually, users will opt for the lighter weight and increased ergonomics,” says Gray.

Published in the January/February 2008 issue of Contractor Tools and Supplies magazine.

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