Battery Powered Lawn Mowers - All Junk - Why?

What will, say, 5 hp-hour worth of batteries weigh? Or cost?

John

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.

Panasonic makes electric razors that use this principle (the cutting speed is kept constant regardless of beard thickness).

---Joel Kolstad

Naaah! Why waste your time. Around here you can get a free electric (with a cord) mower by turning in your gasoline-powered version to the Salt River Project (one of the major power companies here in Phoenix).

Me, I don't own either, my yard/garden maintenance man uses all gasoline-powered tools ;-)

...Jim Thompson

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

Actually, to cut the 300 sq. ft back yard I have, I just have a rotary push mower... 8-)

Charlie

(who might like a battery operated mower, but only if it was self propelled and self guiding... 8-) )

I figure about $2K and 30kg, assuming the density is the same as NiMH AA cells. More cost and less weight for Li cells.

But maybe it could be 1/5 or 1/10 of that, I'm not sure about your assumption. A 1/2 HP DC motor for 2 hours should be fine- and maybe then it's only putting out full power 1/2 the time. At $200-$400 and

Best regards, Spehro Pefhany

Lessee. 5HP-hr is what, 3750WH or optimistically (1.2V/cell) 3125AH. Batteries America has AA 2.3AH NiMH batteries for $2.50ea, so that's about 1360 'AA' batteries, cost $3400 and weigh 40.8kg. ;-)

So did ours, but I decided the exercise was worth the -$600/year it cost to get rid of him. Got rid of the electric mower at the same time and got a midrange gas mower. When it starts to show trouble, it will end up and the end of the driveway and a new one will be bought. Those little IC engines are just too much trouble to fool with, IMHO.

But.. I bet top quality electric mowers would sell well to a certain set. The same kind who were sanctimoniously using Gardena push mowers

Best regards, Spehro Pefhany

We just use Roundup.

John

As a kid in WV I mowed a half acre using a Huffy (brand) electric mower. The only risk, in WV, was you had to mow twice a week in the summer. Otherwise you could lose the cord in the grass and mow over it and cut it into multiple pieces ;-)

...Jim Thompson

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

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.

Best regards, Spehro Pefhany

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

Best regards, Spehro Pefhany

Maybe I don't cut it often enough. If it stalls a lot, is that a sign it's not being cut often enough? ;-) But usually that silliness stops after the spring (have not had to cut it yet in 2005, but all this incessant cold rain will eventually lead to it shooting up once it warms up). In midsummer it's relatively dry and sunny, and the grass slows right down. Anyway, if I cared, which I don't, I'd buy a Honda.

Actually, I may just have been unlucky with those mowers- one seemed to have a material defect- a "rubber" part on one dissolved in the gas, and completely plugged a tiny hole in the carb with goop so the dish wouldn't fill, or couldn't fill fast enough. Another never really liked to start after I ignored it for 6 years or so (even after new plugs etc.). 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).

Best regards, Spehro Pefhany

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

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

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.

Rene

You know those hand mowers? My uncle once mounted a 380V 3 phase 1HP motor on such a mower. He replaced one axle by one he made so the rotating part could be driven by a V-belt. Worked like a charm and not too heavy to handle.

I suppose you could do the same with a 12V or 24V motor and some batteries. Be sure to mount an emergency stop on it.

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