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Old 03-24-12, 07:59 PM   #1
dh1
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Default Sears Lawn Tractor EV Conversion

I have this little Blue Sears, this was the first tractor I converted to battery electric drive and I did to see if I could do it.
http://ecorenovator.org/forum/lawn-g...craftsman.html
I have recently picked up another Sears lawn tractor complete working unit identical to the 1st one, even the model#s are the same, it's a 1981 Sears LT11 lawn tractor. The plan is convert this one into a working lawn tractor that cuts grass.
-Basically remove the 11hp gas engine and install an Etek motor in it's place.
-Remove the pulley off the gas engine and put it on the electric motor.
-Mount the electric motor so that the pulley is in the same spot, position as the it was in the gas version. This way all the belts line up, the trans-axle, clutch, mower deck drive and it's clutch all work the same as before.
-Motor needs 48volts, 4 x 12volt batteries to run at 3456rpm. This is almost the same rpms as the 3600rpms gas engine runs at full speed which is what you would run it at to cut your grass.
-There is no need for a controller since the motor will not over rev, at no load it turns 3456rpm, as you increase the load on it draws more current and try's to maintain the same rpms, acts like a governor on a gas engine. This saves an expense in doing the conversion. All you need is a 48volt contactor which you would have to have if you used a controller, basically a big switch to turn the motor on and off.
-The Etek motor I'm using has a 8HP continuous and 15HP peak 1 minute.
-The output shaft on the Etek that I have is 1"dia, 2-7/8" long, most vertical shaft gas engines have a 1"dia, 3" long output shaft on them. This makes the conversion easy as the gas engines pulley fits right on the electric motor.
-The hardest part is going to be where to put the 4, 12volt Batteries, the bigger the batteries, the more amp/hrs, the better, more run time.
Right now I have the tractor and electric motor.
There are many guys who have done this conversion without a controller using similar parts that I am.
The Motenergy ME1004 is the new version of the Etek that I have, it has the same 1" x 3" shaft and is a more powerful motor.
200amps continuous, 12.5hp
400amps for 1 minute, 25hp peak.
at 48volts.
ME1004 Brush-Type DC Motor
Motor Motenergy ME1004 Permanent Magnet DC Pancake Brushed Double Magnet

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Old 03-25-12, 09:31 AM   #2
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Woohoo, another one.

Yeah thats pretty much the same as my simplicity setup except I have the ME0708 motor with a shorter and smaller diameter shaft. It works awesome.
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Old 03-25-12, 09:27 PM   #3
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How long do these conversions run for on the 4 batteries ? What is the rough cost?
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Old 03-25-12, 09:40 PM   #4
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Quote:
Originally Posted by strider3700 View Post
How long do these conversions run for on the 4 batteries ? What is the rough cost?
I'm not sure on run time, 30 to 90 minuets???
It all depends on the batteries used.
I think the batteries are going to be the biggest expense in the project.
I could go with used batteries, or buy a set from WallMart, or get a set of Trojan 1275's, of spend some real $ on a Lithium pack.

When it's all done I'll post a list of what I spent for this project.
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Old 03-26-12, 07:51 AM   #5
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I'd say I could probably run mine for 90 minutes or so. That would be discharging the batterys very far though. I have 150 Ah batteries which are pretty large capacity wise too. I like to keep run times down to 45 minutes or less though.
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Old 03-26-12, 11:48 AM   #6
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OK so how much lawn are you cutting on a charge then?
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Old 03-26-12, 12:08 PM   #7
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I honestly haven't ever kept track of the time it takes me to mow, but here are my estimates. I have a little over an acre. Its not all grass. I'd say about 3/4 acre to mow. I do about 1/2 of that at once. Its hard to say. It takes (I'm guessing) roughly 30-35 minutes to do the yard area (red). The field (yellow) gets mowed ever 2-3 weeks depending on the weather. It doesn't take but 25 minutes I'd guess since there isn't things to mow around. It also grows much slower than the yellow area.

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Old 03-26-12, 03:59 PM   #8
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Ditto for rough cost please.
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Old 03-26-12, 04:18 PM   #9
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Here is my break down:

~$1235 total

(3) Batteries = $295
Pulleys = $35
Battery rack material = $35
Misc. hardware = $15
Rest = Free (freecycle.org and buddies at the local EV club)
Snowblower attachment (9/9/09) - $100
Two new batteries = $265 (6/4/10) (blew one up & upgraded to 48V)
Chargers = $195 (8/14/10)
Mars ME0708 Motor = $295 (10/22/10)

More info:
http://www.evalbum.com/2984


I could have saved a lot of money by buying more used parts (brand new batteries were almost 1/2 the total cost of the project). However, I didn't have a lawn mower at the time and needed something working to cut the grass! Now that its all together I wouldn't ever want anything else. I really do love it.
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Last edited by Daox; 03-26-12 at 04:25 PM..
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Old 03-26-12, 04:38 PM   #10
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THanks for the info. I'm house shopping for something with acreage and know that my push corded mower probably won't be making the trip with me and would be insane for the property sizes I'm looking at. Also your conversion costs aren't bad at all assuming you can get a free or very inexpensive tractor with a dead engine to start with. Most of the New lawn tractors I've seen are in the $2,000-$4,000 range

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