Cordless Drill Power Ratings
Each cordless drill driver has its power ratings. But how much power is enough to meet the buyer's needs? The answer can be found in what the tool is going to be used for, what the projects are.
Forget the battery specs of volts, amp-hours and so forth for a moment. The projects the tool will be working on is the key. Neither too much nor too little power is good. Here is an simplistic classification of projects that can serve as a basis.
| Scope | Projects |
|---|---|
| Light-duty | Electronics. Kitchen Appliance Repairs. Room Decoration. |
| Medium-duty | Windows, Fixtures Repair & Assembly, Door Installation. |
| Heavy-duty | Large Structure: Deck, Foundation, Fence, Gate, Masonry. |
After you have determined the scope of the project, then check out the power rating of the cordless drill, and decide which one is a good match.
The first thing regarding the power rating is torque. Torque means how powerfully the motor can spin. Normally it's measured in inch-pound or foot-pound. The Dewalt cordless drills employ a different unit. Different types of torque units don't matter much. Generally, the torque capability of any cordless drill is sufficient for most jobs. Only in tasks such as drilling hole in stone, sinking lengthy screws into hardwood constantly, or replacing car tires, do we need ultra-high torque capabilities. For that we will need impact drill drivers or impact wrench.
The other power rating is about the battery. The battery power directly affects our experience of how well the tool performs.
There are 2 aspects in the batter power: (1) voltage, and (2) amp-hour. There's also the matter of the battery type (3), which shows the chemistry of charge-storage elements. The battery chemistry should be carefully considered because it has to do with toxicity to the environment.
VOLTAGE (volt or v)
Voltage is the electrical pressure that pushes the motor to spin. The weight of a battery increases with the voltage as a general rule. The greater the voltage, the more power the battery has to push the motor to produce more torque. Therefore, to match the project scope with the tool's power rating, we look at the voltage.
The voltage can range from 2.4v to 36v for a cordless drill driver. Here is some suggestion on voltage span and project application.
| Tool Size | Voltage | Project |
|---|---|---|
| Compact, Pocket | 2.4v, 3.6V, 4V, 6v, 7.2v, 9.6v, 10.8v | Light-Duty, Electronics, Computers. |
| Regular | 12v, 14.4v, 15.6v | Electrical, Plumbing, Household Projects, Carpentry. |
| Large | 18v, 19.2v, 24v, 36v | Storage Shed, Tree House, Playground Structure. The 24v & 36v are specially suited for masonry or heavy building projects. |
AMP-HOUR (Ah)
Amp-hour is the charge-holding capacity of the battery. The longer the battery can last between recharging, the higher the amp-hour rating. Amp is a measurement of electric current. Hour is a unit of time. Together they make up the charge storage capacity. For instance, a 3 Ah (amp-hour) battery can yield 2 amps of current for 1.5 hours, or 1 amp for 3 hours. Physically, the higher the Ah, the bigger and heavier the battery will be.
Typical Battery Capacities
Compact Size Drill: 1.0Ah
Regular, General-Purpose Drill: 1.0Ah to 2.5Ah
Heavy Duty Drill: 2.0Ah to 3.5Ah.
BATTERY TECHNOLOGY
The chemical elements in the battery determine its storage technology. The storage technology determines its charge-holding capacity, packaging, weight, and friendliness towards the environment. The cordless drill batteries have 3 kinds of chemistry: Ni-Cad, Ni-MH, and Li-ion.
Ni-Cad, Ni-Cd, or Nickel Cadmium, battery is the cheapest and the earliest technology of the three. Lots of models use this type of battery because of its low cost. One concern about this technology is that Cadmium is a heavy metal and toxic to the environment. Appropriate disposal of spent battery of this type is crucial.
Ni-Mh, or Nickel Metal hydride, battery is the following generation technology after the Ni-Cd. It improves upon Ni-Cd in that it holds more charge, and is less hazardous than Ni-Cd for waste disposal. Although higher-priced, it's still a more sensible choice than the Ni-Cd battery.
Li, or Li-ion, or Lithium-ion, battery is the latest state-of-the-art technology. The chief benefit is that, volt for volt, Ah for Ah, it weighs much less than the other types of batteries. It's broadly available and gaining in popularity. It does cost more than the others.
Additional Issues
The batteries need to be recharged on a charger. The chargers are different by voltage levels. A 9V battery can't be recharged on an 18V charger, or vice versa. Fortunately many battery manufacturers now make multi-voltage universal chargers that have solved this problem. Still, a Ni-Cd battery and a Li battery can't share the same charger because of the differences in physical packaging.
The higher the power rating on the battery, the heavier and bulkier the tool will be. The light-weight Li battery has altered this trend. A few years ago an 18v Ni-Cd cordless drill could weigh up to 8 lb., while a 12v at 4 lb. The new lithium battery can get you an 18v drill at 5 lb.! The reduced weight and size is making tool much more comfortable to operate. The premium price of Li battery should come down in the future as demands increase.
