Battery Powered Lawn Mowers - All Junk - Why?

In article <1114529565.980999.315670@g14g2000cwa.googlegroups .com>,
h_markston@hotmail.com says...

I would love to buy or build a high
quality battery powered lawn mower.
Most of the manufacturers that briefly
entered this market got out real quick!
There were a few 36 volt models that
had all sorts of problems. The only
one left is Black & Decker. They've
got a 24 volt unit that runs off a heavy
lead-acid battery. The power to weight
ratio is terrible. Also, they used
a lot of flimsy plastic parts which
forced a recall a couple of years ago.

I know some of the people involved with some of these (nothing currently
on the market that I'm aware of). THe basic reason you see what you see
is cost. Lead-acid batterries are amp-hour for amp-hour a lot cheaper
than the alternatives. They are still, however, more expensive than a
Briggs & Stratton.


Robert

In article <426e8a5b$0$1164$5402220f@news.sunrise.ch>, none@none.net
says...

John Larkin wrote:
On Tue, 26 Apr 2005 18:36:38 +0200, Rene Tschaggelar <none@none.net
wrote:

[snip]

Another aspect beside battery capacity is the
safety aspect. While a petrol powered engine
stops when encountering a root or a stone or such,
an electric engine starts drawing much more power
when braked. Thus a normal motor is inherently safer.



Controls, or even a circuit breaker, would take care of that. An
electric motor has, potentially, less moment of inertia, which would
make it safer in lots of situations.

John,
Are you sure that a 1 or 2 HP electric engine has
less inertia than a 1 or 2HP petrol powered machine ?
While the pseudothreephase asynchroneous machine with
a 90degree cap delivers torque moreless constantly,
a twostroke engine delivers torque only downwards,
requires a flywheel to keep it going plus the balanced
pistons.

The bigger advantage, as far as stopping, is that these (battery
powered mowers) usually use brushed PM motors and shorting them on stop
reduces the speed rather quickly.

Robert

On Tue, 26 Apr 2005 08:32:46 -0700, Holophote wrote:

I would love to buy or build a high
quality battery powered lawn mower.

Just use an ordinary push reel-type mower, and adapt an electric
wheelchair mechanics to drive it.

They're a lot easier on the grass, too, because they shear it instead
of beating the hell out of it.

Have Fun!
Rich

Spehro Pefhany <speffSNIP@interlogdotyou.knowwhat> wrote:

On 26 Apr 2005 19:59:46 GMT, the renowned Ian Stirling
root@mauve.demon.co.uk> wrote:

John Larkin <jjlarkin@highnotlandthistechnologypart.com> wrote:
On 26 Apr 2005 08:32:46 -0700, "Holophote" <h_markston@hotmail.com
wrote:

Electronics has been my hobby and
profession for most of my life.
I use a lot of high quality battery
powered shop and garden tools.
snip
What will, say, 5 hp-hour worth of batteries weigh? Or cost?

Why do we need it to be battery?
AC power, with integral cable reeling would seem an obvious alternative.

After you've spent half your time dragging the cord around trees and
shrubs, and then another half your time splicing cuts in the wires,
you'll most likely happily shell out for a noisy, stinky gas mower.

You miss the point.
It's automatic.
And contains its own wire splicer

Joel Kolstad <JKolstad71HatesSpam@yahoo.com> wrote:

"Spehro Pefhany" <speffSNIP@interlogDOTyou.knowwhat> wrote in message
news:p9ps61lq070cl663hi3cupi06f9b6vicmv@4ax.com...
But maybe it could be 1/5 or 1/10 of that, I'm not sure about your
assumption.

I think you're onto something here -- presumably grass is effectively cut with
the blade spinning a certain minimal speed, so with a feedback control system
the power delivered by the motor could be increased or decreased as needed to
maintain the cutting speed, and in 'light' grass probably nothing near 5HP
would be needed.

Existing petrol ones do this, owing to a nasty tendancy to explode if they
don't.
I suspect that if you really wanted to optimise for energy use,
taking a petrol mower, and replacing the engine with a motor,
and the fuel tank with a battery is a bad plan.

Especially if you're automating it, and the time it takes isn't so important.
Take the speed way down, and go with a more shearing action, rather
than trying to beat the grass into submission with a bluntish blade
going at thousands of RPM.
Of course, as you drop the cutting speed, you can decrease the damage that
happens when you hit a rock.

Hello Spehro,

I figure about $2K and 30kg, ...

That will make for some nice furrows in the lawn. Unless you also throw
in monster tires which can add another few hundred.

Regards, Joerg

http://www.analogconsultants.com

Spehro Pefhany <speffSNIP@interlogDOTyou.knowwhat> wrote:

Briggs and Stratton 4.5 HP, on my third in 10 years.

I think I was overtaken by one of those on the M4 last week!

--
Terry Pinnell
Hobbyist, West Sussex, UK

I don't post very often on any forum.
What usually happens is I think of
some idea or question and by the
time I sit down to type the actual
message my brain power (such as it
is) has been redirected to something
else.

I'm very happy and surprised so
many of you are interested in this
topic.

Batteries have always been 80%
science and 20% alchemy. I'm sure
many of you have read about the
primitive batteries found in the
ruins of several ancient civilizations.
They usually look like a cup made of
stone with a metal rod stuck in the
middle. Anyway, us humans have been
experimenting with batteries for a
very long time!

Batteries have been the biggest curse
and blessing of every circuit designers
life. I can't remember how many times
I breadboarded a circuit with a certain
battery in mind. Every component had
to be chosen with extreme care so that
in end the selected battery would be
adequate for the job.

Maybe in the next few years there will
batteries (or even some kind of fuel cell)
that will allow for the construction of a
really good battery powered electric mower.
It's always nice to dream a little, even if
you're not a kid anymore.

In article <c66u619718buontm7u9eocse63o6a3u423@4ax.com>,
Terry Pinnell <terrypinDELETE@THESEdial.pipex.com> wrote:

I think I was overtaken by one of those on the M4 last week!

That was me in my Skoda Fabia Terry.

Didn't you see the hand waving at you? :-)

--
Tony Williams.

I read in sci.electronics.design that Spehro Pefhany
<speffSNIP@interlogDOTyou.knowwhat> wrote (in
<n5ct61dejtd486io8g9oq6ngv8oggsg3n0@4ax.com>) about 'Battery Powered
Lawn Mowers - All Junk - Why?', on Tue, 26 Apr 2005:

Another never really liked to start after I ignored it for 6 years or
so (even after new plugs etc.).

I found the hard way that *fresh gas* is ***essential***. It's
surprising how gas 'goes off' after a month or three in the tank.

So, out they go in the trash. Some handy(er) man can have them and fix
them (they usually disappear before the garbage man comes).

Yes, I've rescued several. One (electric hover) is on its third owner
after the Lazarus job! It needed one nut and bolt, two washers and
cleaning out.
--
Regards, John Woodgate, OOO - Own Opinions Only.
There are two sides to every question, except
'What is a Moebius strip?'
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk