Re: (ET) dynamic braking

[Michael Neverdosky <MichaelN cycat com>]

Well, 40A at 12V is only 480 watts or about 2/3 HP.
If a 26ah Hawker lasts about 1 hour then the current draw
is only about 20A for about 240 watts, or about 1/3 HP.

Most of the circulat saws I have had are about 10-12 amps 
at 115V, for 1150-1380 watts or about 1.5 to 1.8 HP.
One problem is that these ratings are not listed as to
any time limit or duty cycle.

Horsepower ratings on mowers, like those on air compressors
generally are a product of marketing and have no basis in
reality.
Most gas engines can be counted on to make about half their
rated horsepower. When in very good condition they can do more
but reliablility goes down rapidly. Older engines, like a
typical gas mower after a season or two of use will not do
as well.

Even aircraft engines which seem to be way overbuilt, are usually
only rated for continuous output of 70% of max power.

For electric cars, tractors, movers, etc., the 1 hour rating
is more important than the continuous rating as it is hard to 
carry batteries for much more than 1 hour at high power.

A typical EV motor that is rated 20 HP continous is good for
about 30 HP for 1 hour and often more than 70 HP for a minute
or two.

michael

christopher meier cwix com wrote:
> 
> >Anybody know the hp rating on an electric push mower?
> 
> My B&D 12v 18" model is rated for 3.5hp. I believe the
> power circuit is rated for something like 40amps continuous.
> A 26ah hawker runs it for about 1 hour.  The motor is unmarked
> so I don't know the electrical power rating.  The 3.5hp is
> the gas equivalent number.  It definitely has less power than
> the electrak 3 motor mower deck, which I've never heard struggle
> despite the (grass) load, whereas the B&D will struggle with
> (overly) deep grass (like 2 weeks growth (in MN)).  I normally
> mow every 5-7 days in the summer.  If you want the thing to
> have enough power to cut tall grass, I'd count on something
> like 1kw per 16-18" motor/blade.  If I get around to calibrating
> my power draw meter on my E16 I'll post the current draw for
> my machine.