New electric tractor build

DanC · 04-08-11, 11:03 PM

Hello everyone, i'm new to this site but i've read through a few of the threads and this seems like a great place to get/share ideas. I'm just in the very beginning stages of building a electric riding lawn mower and I was hoping someone with more experience could help me make some decisions. First off, I got my hands on two used motors, both came out of treadmills and both work perfectly. One is considerably older than the other but still in great shape. I've attached pictures of the ratings for each motor but i'm not sure if they will work for my application and if so, which one is the better choice. Secondly, I have yet to actually get a mower to convert. They are posted daily on Craigslist so getting one isn't a problem but i'm wondering if anyone has suggestions on the best (or worst) mower to convert. Really looking forward to starting this project. Thanks for any help.

Dan

Daox · 04-09-11, 08:10 AM

Welcome to the site DanC! We'd love to help out with the mower and I'm glad to see another conversion starting.

Those motors will probably work, but aren't really ideal. The first thing I see is that they're rated at 90V and 120V. That is a lot of batteries. Most mowers are 24-48V. Once you drop those motors down to these voltages, they will spin slower (a good thing since their rated rpms are pretty high), but they'll also consume more amps for the same power output (Volts * Amps = Watts, less volts means you need more amps to get the same watts). The rated amperages for these motors are also very low compared to what you'd see mowing @ 48V for instance. My mower takes ~75A while mowing and it is 48V. If you double the voltage to 96V, you'd be around 37A which is still above the rating on your beefier motor by double what its rated. Now, you can go above the rating on a motor, but then you have to deal with heat. I ran into the same problem with my last motor on my mower. I ended up wrecking it by running too many amps through it for too long without cooling.

As for what mower to pick, just look for one that its going to be easy to mount a motor to and hook it up. That aspect is probably the most difficult part of putting the mower together. I'd also tend to steer toward a slightly smaller mower as it'll use less power and thus smaller motors will be required and less batteries.

I'd highly recommend checking out EV Album to see what others have done. This'll give you some ideas of how others did their conversions, and give you a feel for the stuff you'll need to get it done.

DanC · 04-09-11, 11:58 AM

Thanks for replying Daox. I was afraid that these motors might not be what I was looking for. I'm on a fairly tight budget and I was thinking I would probably end up spending the majority of my money on the batteries so any recommendations on where to find cheap motors? I know fork lifts have good motors but I would think those would be too large. I'm scouring CL and yard sales looking for a tractor, once I find one i'll start posting some pictures of the project.

Daox · 04-09-11, 05:48 PM

For the mower, I'd try freecycle.org. That is where I got my mower chassis. I just requested a mower chassis, or one that was broken down and the person didn't want to fix. I also explained the project a little bit. I even followed up with the guy after getting it put together since he was interested in the project. Perhaps you can even find someone who wants to get rid of a golf cart motor or something. Other than that, I got my new motor off ebay. I was able to nab a mars permanent magnet motor for a fair price which works really well for a mower.

Ryland · 04-09-11, 05:49 PM

Check salvage yards that handle heavy equipment, there are a handful of motors in forklifts, with a range of sizes.
If you have use of a machine shop then I would say to get a golf cart motor, but they don't have an end plate so they are hard to use without being able to fabricate an end plate and mount a support bearing.

mejunkhound · 04-10-11, 05:58 PM

the first motor, 90V @ 10 A does not compute to 2.25HP, more like just 1HP. Typical cunsumer 'hype' rating, no idea how they claim 2.25 HP

the 2nd motor, 120V@18A does compute, and computes to 86% efficient. THus, I's say if you want to use a motor you have, that is the one to use. Motor ratings when stamped with technically accurate ratings tend to be good motors. But you will need to gear it down more than the first motor.

8 ea motorcycle batteries would work. Even better would be a stack of commercial li-ion cells, but you would need electronic skills for the charger. Many of the DIY electric car afficianados use a big pack of AA li-ion cell stacks - but like mentioned, you do need electronic skills to build a good cell charge equalization charger, etc..

For 1/2 hr run time and long battery life you would need about 120 LI 18650 cells MINIMUM, in bulk you should be able to find those new for under $5 each - still an expensive battery pack plus the labor to build the pack and charger.
How do you plan to control the speed? PWM buck drive, or other?

You can also check out surpluscenter.com, they have a bunch of DC batteries.

I've picked up riding mowers for $50 at garage sales, those make great 'donor' vehicles to start with.

mejunkhound · 04-10-11, 06:08 PM

PS: You could always use both motors, one for the tractor motive power and the other for the mower.
More complicated controls though.

DanC · 04-11-11, 10:44 AM

Thanks for the ideas. I believe I have located a free tractor about 1/2 hour from my house. I'm going to go take a look at it on Wednesday. As long as it isn't a total rust bucket I will bring it home and be ready to start the project. As for the motors, I think I will just buy a nice new one. My tax return is coming in soon so I might as well get something decent instead of fighting with a known problem. I also want to build a soil/compost sifter soon so one of these motors might work nicely for that project.

On a side note, I've decided I really don't like Craigslist. I posted a simple post saying that I was looking for a free riding lawn mower and I explained that it didn't need to run etc... and it has been flagged/removed 5 times so far. I have no idea why but re-posting it is really getting annoying.

nibs · 04-16-11, 03:52 PM

I have started a conversion, found a couple of golf cart motors that were chain or belt drive, and therefore had bearings at each end. If the mower final drive pulley is verticle you may want to use a motor which is happy running on its side, otherwise the Mars or similar is perhaps the better choice. The two motors I have were both mounted originally on their side, and am lucky that the tractor has a verticle final drive pulley.

04-08-11, 11:03 PM	#1
DanC Lurking Renovator Join Date: Apr 2011 Location: New Hampshire Posts: 3 Thanks: 0 Thanked 0 Times in 0 Posts	New electric tractor build Hello everyone, i'm new to this site but i've read through a few of the threads and this seems like a great place to get/share ideas. I'm just in the very beginning stages of building a electric riding lawn mower and I was hoping someone with more experience could help me make some decisions. First off, I got my hands on two used motors, both came out of treadmills and both work perfectly. One is considerably older than the other but still in great shape. I've attached pictures of the ratings for each motor but i'm not sure if they will work for my application and if so, which one is the better choice. Secondly, I have yet to actually get a mower to convert. They are posted daily on Craigslist so getting one isn't a problem but i'm wondering if anyone has suggestions on the best (or worst) mower to convert. Really looking forward to starting this project. Thanks for any help. Dan Attached Thumbnails

04-09-11, 08:10 AM	#2
Daox Administrator Join Date: Aug 2008 Location: Germantown, WI Posts: 5,525 Thanks: 1,162 Thanked 374 Times in 305 Posts	Welcome to the site DanC! We'd love to help out with the mower and I'm glad to see another conversion starting. Those motors will probably work, but aren't really ideal. The first thing I see is that they're rated at 90V and 120V. That is a lot of batteries. Most mowers are 24-48V. Once you drop those motors down to these voltages, they will spin slower (a good thing since their rated rpms are pretty high), but they'll also consume more amps for the same power output (Volts * Amps = Watts, less volts means you need more amps to get the same watts). The rated amperages for these motors are also very low compared to what you'd see mowing @ 48V for instance. My mower takes ~75A while mowing and it is 48V. If you double the voltage to 96V, you'd be around 37A which is still above the rating on your beefier motor by double what its rated. Now, you can go above the rating on a motor, but then you have to deal with heat. I ran into the same problem with my last motor on my mower. I ended up wrecking it by running too many amps through it for too long without cooling. As for what mower to pick, just look for one that its going to be easy to mount a motor to and hook it up. That aspect is probably the most difficult part of putting the mower together. I'd also tend to steer toward a slightly smaller mower as it'll use less power and thus smaller motors will be required and less batteries. I'd highly recommend checking out EV Album to see what others have done. This'll give you some ideas of how others did their conversions, and give you a feel for the stuff you'll need to get it done. __________________ Current project - To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. & To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.

04-09-11, 05:48 PM	#4
Daox Administrator Join Date: Aug 2008 Location: Germantown, WI Posts: 5,525 Thanks: 1,162 Thanked 374 Times in 305 Posts	For the mower, I'd try freecycle.org. That is where I got my mower chassis. I just requested a mower chassis, or one that was broken down and the person didn't want to fix. I also explained the project a little bit. I even followed up with the guy after getting it put together since he was interested in the project. Perhaps you can even find someone who wants to get rid of a golf cart motor or something. Other than that, I got my new motor off ebay. I was able to nab a mars permanent magnet motor for a fair price which works really well for a mower. __________________ Current project - To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. & To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.

04-11-11, 10:44 AM	#8
DanC Lurking Renovator Join Date: Apr 2011 Location: New Hampshire Posts: 3 Thanks: 0 Thanked 0 Times in 0 Posts	Thanks Thanks for the ideas. I believe I have located a free tractor about 1/2 hour from my house. I'm going to go take a look at it on Wednesday. As long as it isn't a total rust bucket I will bring it home and be ready to start the project. As for the motors, I think I will just buy a nice new one. My tax return is coming in soon so I might as well get something decent instead of fighting with a known problem. I also want to build a soil/compost sifter soon so one of these motors might work nicely for that project. On a side note, I've decided I really don't like Craigslist. I posted a simple post saying that I was looking for a free riding lawn mower and I explained that it didn't need to run etc... and it has been flagged/removed 5 times so far. I have no idea why but re-posting it is really getting annoying.

04-09-11, 11:58 AM	#3
DanC Lurking Renovator Join Date: Apr 2011 Location: New Hampshire Posts: 3 Thanks: 0 Thanked 0 Times in 0 Posts	Thanks for replying Daox. I was afraid that these motors might not be what I was looking for. I'm on a fairly tight budget and I was thinking I would probably end up spending the majority of my money on the batteries so any recommendations on where to find cheap motors? I know fork lifts have good motors but I would think those would be too large. I'm scouring CL and yard sales looking for a tractor, once I find one i'll start posting some pictures of the project.

04-09-11, 05:49 PM	#5
Ryland Master EcoRenovator Join Date: Mar 2009 Location: Western Wisconsin. Posts: 913 Thanks: 127 Thanked 82 Times in 71 Posts	Check salvage yards that handle heavy equipment, there are a handful of motors in forklifts, with a range of sizes. If you have use of a machine shop then I would say to get a golf cart motor, but they don't have an end plate so they are hard to use without being able to fabricate an end plate and mount a support bearing.

04-10-11, 05:58 PM	#6
mejunkhound Apprentice EcoRenovator Join Date: Apr 2011 Location: PNW Posts: 197 Thanks: 0 Thanked 47 Times in 31 Posts	the first motor, 90V @ 10 A does not compute to 2.25HP, more like just 1HP. Typical cunsumer 'hype' rating, no idea how they claim 2.25 HP the 2nd motor, 120V@18A does compute, and computes to 86% efficient. THus, I's say if you want to use a motor you have, that is the one to use. Motor ratings when stamped with technically accurate ratings tend to be good motors. But you will need to gear it down more than the first motor. 8 ea motorcycle batteries would work. Even better would be a stack of commercial li-ion cells, but you would need electronic skills for the charger. Many of the DIY electric car afficianados use a big pack of AA li-ion cell stacks - but like mentioned, you do need electronic skills to build a good cell charge equalization charger, etc.. For 1/2 hr run time and long battery life you would need about 120 LI 18650 cells MINIMUM, in bulk you should be able to find those new for under $5 each - still an expensive battery pack plus the labor to build the pack and charger. How do you plan to control the speed? PWM buck drive, or other? You can also check out surpluscenter.com, they have a bunch of DC batteries. I've picked up riding mowers for $50 at garage sales, those make great 'donor' vehicles to start with.

04-10-11, 06:08 PM	#7
mejunkhound Apprentice EcoRenovator Join Date: Apr 2011 Location: PNW Posts: 197 Thanks: 0 Thanked 47 Times in 31 Posts	PS: You could always use both motors, one for the tractor motive power and the other for the mower. More complicated controls though.

04-16-11, 03:52 PM	#9
nibs Apprentice EcoRenovator Join Date: Jun 2010 Posts: 206 Thanks: 1 Thanked 18 Times in 17 Posts	I have started a conversion, found a couple of golf cart motors that were chain or belt drive, and therefore had bearings at each end. If the mower final drive pulley is verticle you may want to use a motor which is happy running on its side, otherwise the Mars or similar is perhaps the better choice. The two motors I have were both mounted originally on their side, and am lucky that the tractor has a verticle final drive pulley.