Woodworker's Journal 2002-26-3, страница 46

Makita's new Makstar™ NiMH batteries are available in both regular and higher-capacity versions, including the 3 amp-hour pack shown above (left). These batteries fit Makita's new model BSS730 circular saw, the first cordless saw to sport a full-size 7'/." blade.

Porter-Cable's model BN200V12 brad nailer heralds an interesting variation: The tool runs on either a 12-volt battery, which powers a small internal air compressor, or via an air hose fed by a portable compressor.

Another thing nickel-metal hydride batteries have going for them is higher capacity: Ni-MH cells have a greater energy density than Nicacl cells, so they can hold 25% to 50% more power (depending on whose statistics you believe), allowing for lighter-weight tools with longer run times between charges. Due to their cell chemistry, Ni-MH batteries are also environmentally friendly compared to Nicads, which are considered hazardous waste and must be carefully recycled after they expire.

On the downside, Ni-MH batteries are more costly than Ni-CDs and require a special charger, due to their particular recharging

characteristics (you can ruin them with a regular Nicacl charger). Early opponents of NiMH claimed that these packs discharged more quickly than Nicads and had a shorter life span: 500 charge/discharge cycles instead of the 1,200 to 1,500 cycles common for Nicads. However, Panasonic, a leader in cordless appliance and tool development, says that these reports likely stemmed from tests done with improperly charged batteries. They maintain that Ni-MH packs have a similar life cycle to Nicad packs in actual usage.

Higher Voltage, More Capacity

Since the earliest days of 7.2-volt-powered drills, battery pack voltage and capacity has been steadily on the rise. Pro users'

needs for greater power output and run time have led manufacturers to develop lines of 18-, 19.2- and 24-volt portable power tools and even benchtop saws. Amazingly, the latest 18- to 24-volt cordless models can rival the power output of similar corded tools!

For greater tool run times, some manufacturers have upgraded the capacity of their battery packs by developing special cells that produce more power (a higher number of amp-hours usually equals longer tool run times). For example, DeWalt produces a 2.4 amp-hour 24-volt battery pack, as well as an 18-volt DW9096 XR+ extended run-time pack. The latter

uses 2.4 amp-hour cobalt Nicad cells that DeWalt claims deliver 40% greater run time than standard 18-volt packs. Makita's new Makstar Ni-MH batteries are available in higher-capacity versions, including a 3 amp-hour, 24-volt pack and a 3.3 amp-hour, 14.4-volt pack.

Hybrid Power

Being able to run a cordless tool on an alternative source of power is a real blessing — especially during a busy day when all your batteries are dead. Both DeWalt and Skil have developed optional AC/DC power converters for their cordless lines. If your battery pack poops out, simply slip the converter into the tool, plug in the cord and you're back in action. DeWalt's 24-volt DW0247 and Skil's 14.4-12- or 9.6-volt "Dual-Source" converters give you the flexibility of owning a cordless tool, yet using it as a corded tool with unlimited run time when you need to.

Porter-Cable's innovative new model BN200V12 brad nailer runs on either battery or air power. A 12-volt pack powers a miniature compressor in the tool's body, providing enough air pressure for regular operation — great when you're on a rooftop or away from shop power. Remove the battery (to save weight), and you can power the nailer traditionally, via an auxiliary compressor.

Woodworker's Journal June 2002

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