Mower conversion

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Central Island Lawn
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Joined: 09/20/2010
Points: 3

Okay,
So I'm new to the EV thing and I'm looking for some basic information. I have an older Snapper Rear Engine Rider that I picked up for dirt cheap. The motor is just about expired so I'm looking at replacing it with something more powerful. I would like to have a single motor to power the drive and blade systems, so I would mount it in the same place as the ICE motor was. The motor would have a single on/off switch and I can use the existing clutch and "disk drive" transmission to change speeds. The motor needs to be regulated at a constant 3400 to 3800 RPM for the blade to cut properly.
Alternatively, I would use a dual motor system. The larger motor would replace the transmission and be mounted directly to the clutch/drive chain and I would have a speed and direction control for the drive motor. There is a single clutch/brake pedal which would be used as a engine-shutoff/brake pedal. I would have a smaller second motor to power the blade. The second motor would need to be regulated at 3400 to 3800 RPM as above with a single on/off switch. This would obviously mean more work but would give me more room for batteries as the motors would be out of the way. Either the single or dual motor system would have some sort of operator presence switch, like a grip on the handle or something.
From what I understand about batteries is that they loose voltage as you drain power from them, so a DC-DC converter is on the list of things to have, along with a charge meter and some sort of low voltage cut out so as to not damage the batteries.
My questions are:
1 - How much motor do I need to match a 12HP gas engine? Would golf cart motors work?
2 - How much voltage should I look for? Bear in mind that this machine will see some light commercial duty work.
3 - If the motor is rated at 2000 watts, does it draw 2000 watts constantly or does it draw enough power to keep it's regulated speed up to 2000 watts?

Thanks

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Anderson
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Joined: 10/11/2008
Points: 142
Re: Mower conversion

I have something the size of a garden tractor w/front bucket that I would like to do the same thing with, but in my case I will be using it with the front bucket only which doesn't require continues horse power and the engine/transaxle is connected by a floating drive shaft to the engine which makes the conversion easier.

General Electric long ago made an electric tractor and if you could get one of those that might be the way to go, here's a link
http://www2.ald.net/~roden/ev/pages/et.htm

There was a 12 HP hybrid robotic mower that was similar to a garden tractor but never went into production, see;
http://web.archive.org/web/20060205103505/http://selfguidedsystems.com/

antiscab
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Joined: 07/07/2007
Points: 1686
Re: Mower conversion

Central Island Lawn wrote:

1 - How much motor do I need to match a 12HP gas engine? Would golf cart motors work?
2 - How much voltage should I look for? Bear in mind that this machine will see some light commercial duty work.
3 - If the motor is rated at 2000 watts, does it draw 2000 watts constantly or does it draw enough power to keep it's regulated speed up to 2000 watts?

Thanks

1 - the real question is more like how much power is your current motor actually needing to put out. one way of calculating that is to work out how much fuel it uses in say an hour, and calculate back to energy.

2 - I would suggest somewhere between 24v and 48v.
above 48v and the batteries are too tricky to work with on a mower. below 24v you wont be able to find a powerful enough motor.

3 - motors aren't regulated by power:
A shunt motor will draw however many watts is necessary to hold 3800rpm.
if its rated to 2000W, that just means it can draw 2000W continuous without overheating, and lots more for a short time till it gets to temperature.

If you can't fit much battery (in energy terms) you can get away with a smaller motor, knowing the batteries will go flat before the motor overheats.

I would suggest looking a golf cart motors, or load shift equipment.
Electric forklifts tend to use shunt motors for the hyrdaulic pumps.

Matt

__________________

Daily Ride:
2007 Vectrix, modified with 42 x Thundersky 60Ah
Vectrix 60Ah Lithium Tyres Fuel Registration Insurance cycle analyst 2 x TC Charger & MC
conversion
Spent so far: $5800 + $7000 + $2040 + $1200 + $425 + $800 + $140 + $3000
Cost to do it again: $1000 + $3800 + $2040 + $1200 + $425 + $800 + $140 + $1500 (lasts longer)
Cost for a Petrol bike:$6000 + + $1440 + $7560 + $1000 + $1600 + $4000 servicing
Total spent: $20405
Total to do again: $10905
Total to have used a petrol bike: $21600
Total distance travelled so far: 102'120km

Other vehicles:
2008 Mazda 2 conversion
2009 Blade Electron
1997 Prius - plugin hybrid mod

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