But perhaps the biggest reason for the surge of cordless tools is improved technology. Today’s cordless tools are stronger and more durable than ever before, providing more power and significantly longer run times. And new battery technology is one of the biggest reasons for the increase in cordless tool use.
The first big development in battery technology occurred in the early 1970s with the commercialization of nickel-cadmium. Previously, the majority of batteries were lead-acid, which was heavy and didn’t lend itself well to portable tools. With the commercial acceptance of nickel-cadmium, batteries were smaller, more energy-dense and less expensive. However, nickel-cadmium batteries created environmental concerns when it became evident that cadmium was difficult to dispose of safely. To solve these problems, manufacturers developed an alternative battery chemistry known as nickel-metal hydride.
Although nickel-metal hydride batteries were easier to dispose, they were significantly more expensive. The cost of upgrading to the new battery chemistry was too prohibitive and mainstream adoption was never fully realized.
Then, in 1991 battery technology took a quantum leap with the commercialization of lithium-ion batteries. Comprised of the energy-dense element lithium, lithium-ion batteries delivered an exceptional amount of power in a much lighter package. In these early days, however, even lithium-ion batteries had drawbacks. The new technology quickly powered he development of electronic products like laptops and cell phones, but batteries powered by lithium were too volatile for high-current draw applications. Not until recently have the batteries become stable enough for heavy-duty applications.
The first lithium-ion power tool platform was introduced in 2005. Since then, every major power tool manufacturer has launched its own lithium-ion power tool system. With the introduction of new lithium chemistries like lithium-cobalt, lithium-manganese and others, batteries are now capable of handling applications with higher current draws, making it more feasible to use cordless tools in demanding industrial and construction workplaces.
Lithium-ion batteries last longer and are far less susceptible to voltage depression, common in nickel-cadmium batteries. Known as “memory effect,” voltage depression occurs when a battery exhibits a decreasing charge capacity over time, caused by placing a battery on a charger before its charge has been completely drained or taking it off the charger before it is finished charging. The battery then “remembers” its charge level and recalibrates itself, decreasing charge capacity.
Not surprisingly, lithium-ion batteries also outperform other chemistries in power consistency. Lithium-ion batteries maintain the same charge for the entire cycle while nickel-cadmium batteries tend to slowly lose charge and power as they are used.
However, nickel-cadmium batteries remain competitive because they cost an average of 50 percent less than lithium-ion batteries. Customers often find it difficult to make the switch because upgrading means investing in an entirely new platform – buying new batteries, new chargers, and in some cases, even new tools.
New Trends in Battery Technology
Some manufacturers are addressing this issue by developing “smarter” batteries and chargers. Some of the most advanced power systems on the market now feature batteries with integrated microprocessors that sense battery condition and communicate to the charger. The charger “reads” the battery and optimizes its charge based on the information it receives, improving battery performance and longevity.
Some manufacturers now produce chargers with “renew” capabilities, as well. These chargers force the battery to completely discharge and recharge every time, giving the battery a deep cycle refresh and restoring it to like-new condition. The charger also calibrates battery electronics. For nickel-cadmium batteries, this feature eliminates memory effect, significantly extending usable battery life and decreasing the number of replacement batteries over the life of the tool.
In addition to better electronics, manufacturers have improved the tool-battery interface. The stem pack is the traditional tool-battery interface and has been in use since the inception of cordless tools. It allows users to connect the battery to the tool by fitting a cell into the handle, making the battery more compact and more ergonomic.
However, with a stem pack design, battery weight rests on the battery clips, causing it to eventually fall out with normal wear and tear. Slide packs address this problem by implementing slides on the bottom of the tool housing to hold the battery. The disadvantages of this design include larger batteries and dead space in the tool handle.
In addition, although the battery securely locks into place, battery weight is at the bottom of the housing, causing them to break easily when dropped. The twist pack utilizes the best of both interfaces by fitting into the handle and twisting until locked into place. This twist-lock design spreads the weight of the battery evenly and takes advantage of dead space in the handle.
The Future of Battery Power
Battery technology will not stop at lithium. Manufacturers will also continue to develop new chemistries that are more durable and efficient. Battery capacity will continue to increase, expanding amp-hours while decreasing size.
New technology is also likely to significantly decrease charge time – possibly even eliminating the need for chargers altogether – providing an alternate means of replenishing battery energy.
However, the biggest hurdle for new technology to overcome is still cost, as batteries make up about 50 percent of the total cost of a cordless tool system. Until manufacturers find a way to make it affordable for customers to upgrade to new technology, the market will continue to adopt slowly.
Information courtesy of Ingersoll Rand and Milwaukee Tool Co.