On Thu, 22 Sep 2005 12:31:44 +0100, wrote:

Batteries: higher voltage doesnt just mean more drilling power, it also
means a longer work time from each charge.

I think it has been said before, but drilling time is related to watt
hours in the battery.
Drilling any particular hole requires more or less the same amount of
energy. Whether the cells are the cheap ones or premium makes a large
difference, i.e a factor of about 2. AhxV is where it is at. For any type
of cell, the work time is more or less proportional to the volume of the
battery. As the higher voltages require multiple cells, the cells become
smaller and therefore their Ah rating must necessarily fall. Working on
the approximation that each cell in an 18V battery is the volume of an AA
cell the present ceiling appears to be in the region of 2600 mAh for NiMH,
which if I have done my sums correctly means about 20 minutes at 250W. The
load on the drill is of course variable depending on going conditions.

John Schmitt.

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