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I have embarked on an adventure to convert my really loud 12.5 hp Snapper RER to electric. The main pieces so far are a 48V module from a chevy Volt paired with a ME-1004 48V Shunt motor. This kind of motor is suited for this conversion, as it will pull as many amps as required to run at about 3,800 rpm, which is pretty close to the old Briggs and Stratton. It has the right size and left shaft to allow for the pulley to be swapped over. Because the motor will use a constant voltage and vary the amps, I won't be needing a motor controller. I have a power switch to turn it on, and a contactor to close the circuit on the 48V side and enable the circuit safely. I have pulled off the old engine, and all the wiring harness, 12V battery, throttle cable, etc... We (son and I) cleaned, wires brushed, primed and painted the bad paint areas. So far, we have mounted the switch, the contactor, and the emergency disconnect. I am waiting for a motor mounting plate to arrive, then we'll mount the motor and battery.

I Dunno how much run time, energy to mow... none of that yet. All I have really done so far is take apart a working mower and half build an electric conversion. I am charging it using a computer controlled timer and a big laptop power supply. That part is up and running. It might take a full day to recharge from one mow, but slow charging is better for the battery, and I will literally have a week between mowings to recharge.
 

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A couple of these pics are a few days old. The ignition switch has been replaced by a pushbutton. It's a latching on/off switch. I will be able to reuse a couple of the wires from the old ignition switch.
 

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The throttle cable has been replaced by a big red button that I can push to kill the power to the motor if something goes wrong. The area where the 12volt battery was located was corroded and the paint was bad. It was wire brushed to bare metal, naval jelly applied, then primer and paint. Looks pretty good now. Up under there, you can see the contactor that will act on the info from the power button. It should apply voltage to the contactor, which will close big contacts to let power to the motor.
 

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This is where I am today. I got the 1/2" thick, water jetted mounting plate for the motor yesterday. Here it is in position on the motor, and a second pic of it where it will go on the mower. I am currently trying to get the pulley off the old engine to transfer it to the electric motor. Looks like I'll have 3 of the 4 bolt holes needed already. Will have to drill one. I need to make sure that the crankshaft centerline is in the exact same place as it was with the gas engine.
 

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Hey Richard!

Funny enough, I just bought pretty much the same Snapper RER as you, except mine came with the Honda engine. Should it ever blow up, perhaps I'll run with what you're doing here. Well, maybe after I try to put an extra spark plug in the combustion chamber first!

Look forward to the updates.
 

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Here is the pulley on the old engine. I had to heat the pulley with a butane torch, and quench it. Then, I buzzed it with an air hammer and it came off. I got it set to the same measurement from the bracket and tightened the set screws. The photo with the paper shows the old boltholes with pencils stuck in them. The edge of the blue tape is about the centerline of the two axis. The star shaped paper is a rubbing of the new motor bolt pattern. 3 of the 4 required holes are already there. I had to drill a single hole, and the plate lines up well. It should be fine, but I did want to double check the electric motor centerline versus the prior gas engine centerline.
 

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Discussion Starter #7
I built a thick wooden spacer to set the battery on. I need this, as the deck has some ribs in it for strength, also the cable that actuates the drive passes under where I wanted to place the battery. The wooded shim was made from blocks of 3/4" maple, two layers high, with a deck of a single piece of plywood that fits between the seat bracket and the motor. I extended the threaded rods that hold the battery pack together thru the metal deck, with fender washers and nyloc nuts below.

I found a place in Houston called Texford battery that made some custom battery cables for me. I bought him some 1/0 copper welding cable for him to cut, strip, and put new ends on. They also sell colored rubber boots, either black or red, to cover the bolted lugs at the motor, battery, and other devices. I wired up the big wires, then pulled out the ignition harness that fed the ignition switch at the steering shaft. I replaced it with some 10 conductor irrigation wire, which gave me enough wires to control both the on/off switch, and the gauges.
 

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Test drive has gone really well. It makes noise, but nothing like before. No big deal to hop off and move a dog toy, then get back on and start it up again. I'll have to keep an eye on what the discharge rate is while mowing the lawn. Swinging the blade takes more juice than just driving around, about double in fact. The current draw is not too bad. 20 amps rolling, 50 amps cutting. I calibrated the meter last night. I'll post a link to it running on youtube when I get a video up.
 

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No, I bought it on eBay. Nearly everything was from eBay, in fact. Motor, battery, guages, contactor, disconnect.

I haven't been to a junkyard in Tooooo long. Do you come down to Houston at all anymore, Brad ? We'll go.
 

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How are you handling the blade engagement? Electric or mechanical engagement clutch? I have a MTD Yardbug I have been noodling doing the same thing with, but in the effort to extend battery life, I am considering using separate motors (different ratings) for propulsion and blade control. Starting with the blade operation to determine the torque required to move varying types and growth of grass to determine proper motor sizing. Propulsion is much simpler as my land is pretty much flat so torque load is just what is needed to move my fat but around the yard. Your thoughts?
 

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If the mowing blade has much "wing'' on it you could try cutting it down to lessen the amount of air the blade is moving. I had a Simplicity that came with high lift blades for a long missing bagger. The amount of air those blades moved was amazing. I cut off about 75% of the wing and dramatically reduced the air flow and noise.
 

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I haven't been to a junkyard in Tooooo long. Do you come down to Houston at all anymore, Brad ? We'll go.
No, I'm long gone from NetIQ, which was my excuse to visit Houston (and the 3 Houston Pull-A-Parts). I actually visited Harry's U-Pull-It in PA last week. I'll likely visit my favorite PA yard in PA on the way to Carlisle in 5 weeks. They also have a lawn mower section! :tango_face_smile_bi
 

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Just a couple of observations.

#1. I see some excess toe out. This causes drag so it would be worth your time to get the wheels pointed dead straight with no slop in all the steering joints.

#2. I hear what I take to be a lot of bearing noise from the transmission and the deck. If the bearings are noisy they are creating more drag. Check them out. Also, if the chain and sprockets are worn they create a lot of drag.

I would use double sealed bearings in the deck spindle with just a bit of grease wiped on everything else inside the spindle to stop corrosion.

It would be interesting to do before and after amp tests of these changes. Hopefully the repairs would make a noticeable difference but sometimes you do a lot of work for very little gain :)
 

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Discussion Starter #17
Thank you for the advice. I actually already had bought the steering bushing kit, but had not done anything with it until yesterday, after your post. I re-did the steering and replaced the worn parts. It is much nicer to drive now.

I don't know what to think about the noise you heard. Some of it is the belt that runs the blade that is flapping around when the blade is not engaged. There is no chain or other parts... ?? I am not sure about the sealed bearings in the spindles. Perhaps you are thinking of a different mower design ?
 
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