Is a 12-volt battery-powered impact wrench as powerful as a 28-volt battery-powered impact wrench? Is “bigger” always “better” when it comes to selecting battery-powered tools for farm use? Is a lithium-ion battery better than a nickel-cadmium battery?
Yes. No. Not necessarily. Voltage, size and type of battery are intertwined considerations when selecting a cordless tool for farm use. Voltage is a good place to start.
FACTOR IN VOLTAGE
Technically, a 12-volt battery-powered tool has as much “power” as a 28-volt tool, but the 28-volt has more torque.
Merriam-Webster says torque is, “…a force that produces or tends to produce rotation…” When you strain to loosen a wheel lug bolt but nothing moves or moves slowly with effort, that’s “torque.”
Power is work accomplished in relation to distance and time. Torque first loosens the lug bolt, then power removes it.
That means a 12-volt, battery-powered drill has plenty of power for jobs that don’t require much torque, like drilling soft woods or sheet metal. Jobs that require torque, like drilling holes through oak railroad ties or ½" steel plate, are better suited to high-voltage or high-torque cordless tools.
Voltage also influences the size and weight of a tool and its battery. Increased voltage means heavier, bulkier and more expensive tools and batteries.
It’s fine to occasionally heft a 12 lb., 1"-drive 18-volt cordless impact wrench to remove a dozen stubborn tractor wheel lug bolts, but a 4 lb., 3/8"-drive cordless impact is more convenient for a day spent underneath a big field cultivator replacing sweeps.
BATTERY PROS AND CONS
Amp-hours determine the run-time of a tool and its battery. A battery’s amp-hour rating is comparable to the fuel tank on a tractor. The harder you pull a tractor the faster it consumes fuel. The same applies to battery-powered tools: The harder you work a tool, the more amps it uses and the quicker the battery will need to be re-charged.
A battery rated for 4 amp-hours should supply 4 amps for 1 hour, 2 amps for 2 hours, or 1 amp for 4 hours.
Nickle-cadmium (Nicad) and Lithium-Ion (Li-Ion) are currently the two main types of batteries used with cordless tools. Nicad batteries are less expensive and offer between 700 to 1,000 charge cycles. But they can develop a “memory” that shortens useful battery life if they’re not completely discharged before recharging.
Li-Ion batteries are more expensive, lighter and more compact than Nicad batteries of the same voltage. Li-Ion batteries provide 400 to 750 recharge cycles, don’t develop “memories” and provide full power until the battery is nearly discharged.
Read more from Dan Anderson:
The New Generation: Not Your Grandfather’s Box Drill
Procuring Farm Machinery Parts: The Big Picture
