On 18/12/2020 12:51:55, The Natural Philosopher wrote:
On 18/12/2020 12:38, Fredxx wrote:
On 18/12/2020 12:06:39, The Natural Philosopher wrote:
On 18/12/2020 11:18, Andy Burns wrote:
PeterC wrote:

Bosch 10.8V are now 12V but can be used with the 10.8V battery.

That's just the old marketing vs technical MOAAR POWAH! argument

3x3.6V = 10.8V nominal or 3x4V=12V fully charged
5x3.6V = 18V nominal or 5x4V=20V fully charged
10x3.6V = 36V nominal or 10x4V=40V fully charged

Actually its 3.7V and 4.2V

3x3.7V = 11.1V nominal or 3x4.2V=12.6V fully charged
5x3.7V = 18.5V nominal or 5x4.2V=21V fully charged
10x3.7V = 37V nominal or 10x4.2V=42V fully charged

Of course the voltage is supremely irrelevant and goes back to the
days when all there was was a 600mAh 1.2v sub C nickel cell. If you
wanted more capacity you had to stack em in series.

And you can wind a motor for any voltage you want. And build a
lithium cell to any capacity you want...

Contact resistance and electronics tend to favour a higher voltage
lower current. The limit being what is considered safe for the human
body and how many cells you can get in a package.


Not necessarily. There is a broad sweet spot between 10v and 200V. and
10A an 100A. Contact resistance doesn't come into a modern variable
speed brushless.

Battery contact resistance and general wiring in a cordless tool can be
significant. I think an earlier post established a typical stall current.

100V would not be tolerated in a system that has unshrouded terminals.
Hence why 60V systems are going to be as high as they're going to get.

And calculations show that where motors are concerned the same weight of
copper in a few fat turns or a lot of thin ones ends up the same if you
adjust the voltage..

There is a gradual loss of efficiency of windings with thin wire where
insulation takes a higher proportion of wire diameter. I doubt that will
be much of an issue with cordless tools.

To be sure if you are cheapskating the power FETS a higher voltage lower
current is a bit less demanding in terms of 'on resistance'

This is all about cost.

And wires in excess of 100A get pretty unweildy.


For extended periods, yes, as do contacts.