Battery-Powered Tools Kalispell MT
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Battery-powered tools are handy to use around the house, offering convenient mobility and, usually, enough portable punch for most home tasks or projects. They free us from the tangle and tether of extension cords and, when outdoors, eliminate the possible shock hazards of line voltage.
Today's cordless dynamos from reciprocating saws and screwdrivers to hammerdrills, rotary hammers, circular saws, cutoff tools and metalworking tools are often leaps and bounds ahead of their predecessors. For the most part, the tools are better designed and most significantly run on battery packs with high levels of reliability and performance.
Many manufacturers offer groups of tools that all work off the same battery pack, eliminating the need to invest in and have on hand a variety of backup batteries. One size generally fits all within a family, so if you are working with a 14.4-volt battery-operated drill, the battery pack will usually fit into a 14.4 circular saw of the same manufacturer. There are two kinds of batteries for cordless tools, nickel cadmium (NiCd) and nickel metal hydride (NiMH). Both types are available in battery packs of various total voltages.
In the United States, most manufacturers only offer NiCd battery packs for their cordless tools because of the widespread consensus that NiCd has the more robust chemistry and better overall properties for the applications. Though NiMH batteries have somewhat longer run time per charge and the advantage of not containing toxic cadmium, they can only be recharged about half as many times as NiCd batteries (about 500 times compared to 800 to 1,000 times). Also, they generally cost more and are more susceptible to losing ability in extreme cold. Even though NiMH batteries have yet to prove themselves the best choice for power tools, they have generally replaced NiCd in other applications, so keep an eye on this technology for future purchases.
Rechargeable NiCd batteries are alkaline storage batteries (sealed secondary batteries i.e., batteries that can be recharged) that use nickel hydroxide as the positive electrode, a cadmium compound as the negative electrode, and potassium hydroxide as the alkaline electrolyte. This cell chemistry makes them well suited for power-tool applications of extreme current draws and a lot of on-and-off activity. For use in power tools, NiCd power tools are available in a range of voltages, typically from 7.2 volts to 24 volts, and less commonly, 36 volts.
A battery pack that can run a cordless tool is composed of multiple individual 1.2-volt NiCd cells clustered either radially, upright and parallel, or lengthwise and linear, connected by nickel plates and covered with a heat-shrink tube. (A 9.6-volt battery, for example, has eight 1.2-volt cells.) The outer case of a battery pack, which is designed by the tool manufacturer to fit the tool design, is determined by the pack configuration and by the number of cells used to comprise the pack. Typically and unfortunately, the packs are not interchangeable among manufacturers.
With NiCd batteries, the voltage stays practically constant throughout the discharge, even during high-current discharge, unlike standard household batteries, where the voltage drops from use. But among battery packs of the same voltage, ampere-hours (Ah) the amount of energy stored in the cell can differ, affecting run time between charges. Amp-hour ratings for NiCd batteries are 1.4 Ah, 1.7 Ah, 2.0 Ah, 2.4 Ah and 3.0 Ah. For instance, each 1.2-V cell rated at 2.4 ampere-hours in a battery pack will provide 2.4 amps of current for one hour, explains Jeff Wilkison, product manager for cordless tools at Bosch Tools. The important thing to keep in mind is that the higher the amp-hour rating, the longer the run time.
The amperage drawn from the battery varies by task the more strenuous the application, the more amps it requires and the less run time derivable from one charge. Putting in a screw can take less than 10 amps, while cutting into heavy material could take 30 amps, notes Christine Potter, product manager for cordless tools at DeWalt. Likewise, with a single charge on a drill, though you could put in 500 small drywall screws on a single charge, with the same unit you may get to drill 100 holes with a ship auger bit.
When deciding which size tool or tools to buy, take your overall needs into consideration. If you are only looking at a drill and not any of the cutting tools, a 14.4-V unit offers the optimum balance of power and size and weight. However, if you need a cordless circular saw and a cordless reciprocating saw, then I usually recommend people use 18-volt models, because 18 volts for cutting tools is optimum,Potter says. Industry-wide, 18 volts is the most popular because of the combination of power to weight, she notes. The convenience of using one size battery pack and one battery charger for all the tools may override any small deviations from ideal performance in some of the tools.
Best Charging Practices
There are no memory characteristics in batteries used in power tools, says Joseph Carcone, vice president of marketing and sales at Sanyo Energy, the world's largest manufacturer of rechargeable batteries. The life of a battery is truly a function of how many charges and discharges it has. And partial discharges are, in fact, more beneficial for long life.
Not all chargers work the same way or take the same amount of time. Some units charge at a constant rate and monitor battery temperature, shutting down the charging process when the temperature spikes to a certain level, to avoid overcharging the battery. More sophisticated chargers have a three-stage charging process.
Fast charge quickly handles most of the recharging.
Equalization balances out the charge, bringing each cell up to full charge.
Maintenance is a trickle charge that maintains the full charge of the battery pack while it is still on the charger, awaiting use. (Otherwise, even when not used, once fully charged and off the charger, NiCd batteries may have up to 10 percent discharge within 24 hours, notes Carcone. So keeping them on a three-stage charger until the next project ensures full charge.)
Three-stage chargers can be either one-hour fast chargers, which provide the maximum charge within one hour, or 15-minute chargers, which do the same in a quarter the time. In all three-stage chargers, the amount of current that can go into the cell is a function of temperature and time. In a 15-minute charger, a lot more current flows into the cell than would flow in a one-hour charger, so the sensitivity of the monitoring has to be more accurate so the sensor events are not missed and the cells do not go into thermal runaway and possibly lead to cell venting.
Overheating batteries shortens their life expectancy. Three-stage chargers, which do not extend the battery into high temperature, probably help sustain battery life better than a single-stage charger, which terminates the charge when the batteries reach a very high temperature,Carcone says.
The LED (light-emitting diode) on the charger merits attention. Distinctive colors and/or blink patterns indicate status, including such information as: ready to charge, charging, fully charged; battery too hot to charge and therefore charge delayed; defective battery do not charge and replace the pack; and problem with power line, which could be important if you are charging off a generator. Chargers for large batteries, such as 24-volt and above, might include a fan to keep the battery pack cool when charging.
All batteries of the same Ah and voltage are similar in terms of charge and discharge characteristics but may be manufactured differently to accommodate manufacturers price points. Typically, batteries marketed as high performance have better characteristics. Inexpensive batteries may not have uniformity from cell to cell and therefore may have a wide variation in their capacities, resulting in a much shorter product life. In all likelihood, a name-brand tool manufacturer marketing a tool as professional grade will couple the tool with a quality battery pack.
The sub-C is the most prolific cell used in the power tool market. It is available in various Ah ratings, from 2.4 Ah down to 1 Ah. However, at the lower end, a manufacturer selling a tool at a low price may not include the Ah rating on the battery, and therefore, the consumer could be buying much less run time compared with a product from a manufacturer using high-end cells. So it is best to make sure you know the Ah rating of the battery you are buying.
William and Patti Feldman are a husband-and-wife freelance team based in New York.