Printable View
Trying figure out how much electricity these 2 drills use.
1. 8 Amp corded drill used for 2 hours
2. 24 Volt Cordless drill with a 2.0 Amp Hour lithium Battery.
What uses more electricity? The corded drill for 2 hours, or Charging the 2.0 Amp Hour battery?
Depends completely on how loaded the drill is. If running a light load both drills will consumer less power. In general with battery power, there is wasted energy in the heat loss in the charger, and the heating of the battery when in use. But with the data you shared the question is not possible to answer.
Watts is a measure of power. Energy consumed is measured in watts per hour. In your corded example the drill fully loaded (almost stalled) would consume 8 amps. Voltage is 120 volts. Watts would be 120V times 8A = 960 watts. We don't know how much current the cordless drill consumes. We do know the battery is 24 volts and 2A hours. That means it can supply 24 volts at 2 amps for one hour.
The corded drill would use more electricity because the cordless would die well short of running for 2 hours.
I've never seen studies comparing the efficiency of corded vs cordless drills, but I tend to think that the cordless would do more work for a given quantity of energy. There is little incentive for a manufacturer to make an efficient corded motor, whereas in the cordless arena, getting the most out of what a battery will give is paramount. There are losses with charge/discharge, but I don't think those are huge.
Quote:
Originally Posted by Joe Jensen
960 watts times
two hours =1900 watt hours
say one amp times 24 volts for two hours= 48 watt hours
Way too many variables to even begin.
This is not a simple question.
The way the question is asked, the specs on the charger are needed & those vary wildly depending on brand.
It would be very difficult to estimate due to very significant energy conversion losses -- easier to actually measure the current draw.
You can't just figure wattage, as there are major energy losses in conversion from electrical-to-chemical during charging, and chemical-to-electrical-to-mechanical during use -- easily losing as much as 60% (based on major power-generation plants' 40% conversion efficiency -- slowly approaching 60% efficiency in the most efficient new power plants -- where they REALLY optimize efficiency). This is one of the great fallacies of electric cars -- they're actually more wasteful of energy than direct fuel-to-mechanical due to energy conversion losses when you figure the ENTIRE process.
I believe if the drills produced equal power across the board the cordless would take more input power due to energy loss on charging and because it is operating at a lower voltage
That being said the drill probably doesnt produce the same power as the corded and will only last a short while running.
Again guys the question is this:
"
What uses more electricity? The corded drill for 2 hours, or Charging the 2.0 Amp Hour battery?"
The OP is asking if the battery charger uses more electricity to recharge the battery than the corded drill uses.
2 hours of corded use vs 15 minutes of charging. (not even looking at the corded drill or what power is lost in the battery)
I would have to say the corded uses more power. The couple of chargers I looked at for the 24 volt were rated at similar amperage to the corded drill. Even if it took 30 minutes to charge over 2 hours the drill would use more
So to make it as simple (and unrealistic) as possible, if we ignore all of the losses and efficiencies and all of the other real world factors that make this a difficult question to answer; The 24 volt 2 amp hour battery contains 48 watt hours ofenergy and using the 8 amp 120 volt drill consumes 960 watt hours of energy per hour.Using the corded drill at full output power for two hours consumes 40x more energy than the battery contains.
Quote:
Originally Posted by John Lanciani
But then the question is - how long will the cordless drill run under full load before the battery dies? Much more information would be needed here to get anywhere close the an actual factual answer.
David
Start at the "other" end - if both drills do the same work for the same period of time, they are outputting the same mechanical power.
Both have some inefficiency in converting their input 120V into mechanical power. The corded likely has brushes (lossy) and may not be designed for efficiency (no real need). The cordless might be brushless (more efficient) but there are losses in charging and discharging a battery.
For a particular set of example drills, you could measure and compare. But there's no general answer.
But then the next question is, "Who believes that a corded drill will run for 2 hrs at full load and not melt?"Quote:
Originally Posted by David Buchhauser
Followed by, "Who makes it?"
Followed by, "How does it compare to Festool?"
Followed by, "When do they go on sale?"
Followed by, "Does that include shipping?"
;)