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-   -   Cordless drills, take two (http://www.diychatroom.com/f29/cordless-drills-take-two-151529/)

 Yoyizit 07-25-2012 05:36 PM

Cordless drills, take two

Drilliing many holes needs energy delivery = watt-hour delivery = voltage x amp-hour delivery

Fast drilling of holes needs power delivery = watts = volts x amps = high (rpm x torque)

This example Ragone chart
shows that, for a battery of a given weight, you can't have a battery optimized for power delivery and energy delivery at the same time, so you are kind of forced to decide which is more important.
If weight is important, this same chart can steer you toward a weight/energy/power tradeoff.
The trick is to find a chart showing all the battery technologies commonly used today in cordless tools.

In the event of a tie between tools, for which do you get the more w or w-h or the less weight, per dollar spent?

 toolaholic 07-26-2012 06:18 AM

Quote:
 Originally Posted by Yoyizit Drilliing many holes needs energy delivery = watt-hour delivery = voltage x amp-hour delivery Fast drilling of holes needs power delivery = watts = volts x amps = high (rpm x torque) This example Ragone chart http://www.google.com/imgres?imgurl=...Q9QEwAw&dur=95 shows that, for a battery of a given weight, you can't have a battery optimized for power delivery and energy delivery at the same time, so you are kind of forced to decide which is more important. If weight is important, this same chart can steer you toward a weight/energy/power tradeoff. The trick is to find a chart showing all the battery technologies commonly used today in cordless tools. In the event of a tie between tools, for which do you get the more w or w-h or the less weight, per dollar spent?
Boy your really into science of batteries. I use the Milwaukee 18 nicad/ V18s for the heavier stuff if they don't cut it, out comes the corded stuff. And some projects like drilling out tree stumps and drilling holes in the ground with a earth auger dictate passing on cordless and going straight for the cord!

 Yoyizit 07-27-2012 08:33 AM

Yeah, the cord gives you high watts and almost infinite watt-hours.

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