# Three Phase Electric riding mower utility vehicle project



## PStechPaul (May 1, 2012)

I thought I had a thread here on my electric riding mower project, but apparently I only briefly mentioned it in my introductory post, and then posted some pictures, videos, and information in various places. I have a more complete thread at http://www.mytractorforum.com/showthread.php?t=230278.

Perhaps I should have a complete build thread, or a web page with all the details and the trial and error process that I've gone through on this project, but for now I'll post the latest video of what I have done on this "toy":





 
It's been about a year since I last did anything with it, and when I pulled the tarp off I found part of a mouse nest in the opening on top of the motor. But it was not really very much and I was able to fish it out with my fingers and a screwdriver. Some time ago I had left the tarp off and there was water in the motor from a heavy thunderstorm, but I dumped it out and it seems not to have caused any damage.

First I put the machine on its side and I found that the drive pulley of the transmission could be turned two revolutions before it would start rotating the chain drive to the rear axle differential. But it seems that it has this excessive free play only in reverse, although the forward gears still require about 1/4 turn to engage. 

I used an old (1999?) vintage 17 Ah 12V SLA battery that I have frankly abused and neglected, but it still holds a charge and was able to supply about 15 amps to a 12V to 220VAC 1000W inverter that I modified to get 270 VDC, which I connected to the DC link of my 2HP VFD to the motor. The motor turns but it is noisy and draws about 120 watts with the transmission in neutral, but I think most of that power and noise is the transmission and drive pulleys.

The battery is back on charge and tomorrow I plan to use it to take a short ride to see what sort of power I can get. I think I should be able to run on about 400 watts which is the continuous rating of the inverter, as long as the voltage doesn't sag below the 200 VDC limit. Already it is down to about 220, but the battery voltage was sagging to about 11.5 volts even at 15 amps. Hopefully the fresh charge will work for a short run. 

For this little tractor, I will probably complete it using either the 4 12V 12Ah SLAs I have, in parallel, or maybe a deep cycle 100 Ah marine battery I can get from Walmart for about $75:
http://www.walmart.com/ip/EverStart-27DC-6-Marine-Battery/16795212

It should provide the 30-40 amps I will probably need for about 20 minutes to 1/2 hour or so. That's enough for now. Then I might get a 1500W inverter with 24VDC input, and get another battery so I'll be able to run for about an hour of light duty and hopefully be able to tow a cart with several hundred pounds of firewood. The real test will be (if I dare) to take it up to the top of the hill which is a rough 10-20% grade. It would go up empty, and down with a load. But I'm a little concerned about the braking ability of the tractor. Like many small tractors, it uses a small disc brake on the transmission, but if a rear tire loses contact with the ground, the other can spin. On my Simplicity Broadmoor, one of the axle pins sheared off, which is even worse. Maybe I'll install a set of disk wheel brakes designed for a go-cart, or maybe some brakes from junk motorcycles...


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## PStechPaul (May 1, 2012)

I decided to take some of the tractor apart and do a good cleaning and inspection. I pulled off the hood and seat assembly and found some rust, but nothing too serious. However, I found that the brake seemed to be inoperable, and I think it may be missing a part. I wire brushed most of the deck where it was rusty, and it looks much better, especially after a quick spray with gray primer. There are two metal pins that seem to function as caliper brake pads which would press against the disk, but they are too short to make contact. The actuation lever has a bent portion that would push on these pins if they were longer, or if there were an extra part like a real brake pad with pins to match the pins already there.


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## toddshotrods (Feb 10, 2009)

Hey Paul, great to see a thread and progress on this. You suggested it in my thread asking if there was a way to test AC motors with a 12v battery like we do DC motors.

I actually came up with a way to make the motor I have functional in an upcoming project. Not a cheap 12v test, but a marginally useful motorcycle. I have been using these little Razor scooter batteries in Scrape for a year now and I am really impressed with them. Of course, being lead, the range is horrible but I have completely abused these things, running them far below any reasonable DOD, and drawing (for what they are) huge amounts of current from them repeatedly.

So, I started thinking that I could actually string up 20 of them in series, to the DC bus of a VFD and use my little motor in the bike. They should last even longer, and perform much better, because I wouldn't be pulling as much current with the high(er) voltage AC motor/drive. Battery weight would be reasonable at 100lbs, and the box size would lend itself well to upgrading to lithium later. For the time being, the bike would have (in theory) 5-10 miles of range with very light surface street usage.

Now I just need to get enough irons out of the firs to give it a shot...

I'm don't know if they would work in your tractor, but thought it might be worth mentioning.


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## PStechPaul (May 1, 2012)

I'm planning on using that approach for my other tractor project which will use my 1967 Simplicity Broadmoor which has a cutting deck, dozer plow, and traction chains, and originally had an 8 HP B&S engine which I plan to replace with a 5HP three phase motor which I bought for $50. I have a thread on that at:
http://www.mytractorforum.com/showthread.php?t=344129

I found some 100 Ah 12V deep cycle batteries at Walmart for only $68 each, so I will try one and maybe eventually use two of them with a 24V 1500W inverter. I figure an average power of about 600W and I should get about an hour of riding time with one and more than 2 hours with both. I won't have regeneration at first, but I might be able to rig up a switchmode power supply/charger to the DC bus and charge the batteries from that. It sounds like an over-unity range extender but I will set it up so that it only kicks in when the bus exceeds the 270 VDC nominal I get from the batteries and inverter, so it should only charge them when going downhill.


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