Friday, October 17, 2014

How long 18v 3Ah lithium ion drill battery last until recharge

Given data:
DEWALT 1/4 inch, 18 volt
Cordless Drill Driver ($100 price)
Average Power consumption: 250 watts
Ave. Amperage/Current draw: 7 Amperes
No Load Speed: 0-4,000 RPM
Chuck Size: 1/4 inch (6mm)
Gear Reduction: Single
Maximum Torque: 1300 in-lbs (150 Nm)
Power Source: 18v 3Ah Lithium Ion battery
Battery Recharge time: 30 minutes

Calculation of Running Time:

(Example: Carpentry, Home Project Renovation)

If I use this power drill to drive 2 inch screws in wood,
how long does the 18 volt, 3 ampere hour capacity
Li Ion battery last until my next recharge?

Total Available Energy at full charge = 3 ampere hour = 180 ampere minutes

Average time to drive one 2 inch screw in wood: 3 seconds (0.05 minutes)

Average Energy used to drive one 2 inch screw = 7 ampere x .05 minutes = 0.35 Amp min

Battery Run Time = 180/0.35 =  500 minutes = 8 hours

Recharge the battery after 8 hours of total usage
This calculation is based on drill being used on 2 inch screws only
Battery will last longer or shorter depending on load and application
The harder the task (bigger screws, harder wood, etc.),
the more current draw, the more power consumption,
the more energy required,
the lesser the battery life before the next recharge

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