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Hi everyone. This might be a bit uncommon but I was planning on doing a conversion of a tractor, this cool old thing: https://en.wikipedia.org/wiki/Allis-Chalmers_Model_G. I was hoping to use a 2013 Nissan Leaf (might be a bit overkill but not afraid to pop wheelies haha) that I might buy, it is going on auction soon.
I already own the tractor. I also currently own a 2015 Nissan Leaf, but I am saving that for personal use. I'm a software engineer (hopefully that can be of some use) and I don't have too much mechanical experience but my brother is a mechanic who works a lot on farm tractors. I've seen these two methods for controlling the Nissan Leaf motor: http://productions.8dromeda.net/c55-leaf-inverter-protocol.html (this looks best) and https://www.thunderstruck-ev.com/dilithium-vcu.html but I have trouble understanding what I am looking at as I don't have much experience.
It looks like the motor can be controlled over the CAN bus but it seems like additional pre charging circuit or something is needed, was hoping to just use all the components in the leaf. I was hoping to use the batteries (preferably 1/4 of the batteries in a leaf since it's a small tractor), battery charger, and the motor from the leaf and do as little soldering/wiring as possible. Any guidance is greatly appreciated
 

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Sounds interesting - have not seen an electric tractor on here before :)

One point - if you plan to use 1/4 of the Leaf's batteries yet use the complete drivetrain from the Leaf - you're going to run into voltage problems. The Leaf battery pack is relatively straightforward to dismantle into its modules - but the modules themselves do not readily break down any further. I don't know the minimum operating voltage of the Leaf's motor controller - but if you plan to use only 1/4 of the batteries - you will not reach the 380VDC that the Leaf runs at stock. The older Leaf modules each contain 4 cells, configured as 2 series groups of 2 cells in parallel. The newer modules can be considered the same as two older ones stuck together - they're 4 series groups of 2 parallel cells.

If you use 1/4 of the modules of an old Leaf (so 12 modules) you will have a 24s battery configuration - meaning your voltage will only be ~90V. A 90V battery pack is definitely not going to run the Leaf drivetrain. So your options are either to find smaller batteries (i.e. each cell/module is lower in capacity, but you connect more in series), or to find a drive solution that is capable of being run at the lower voltage of your 1/4 Leaf battery pack.
 

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Lower than the Leaf's design voltage is an issue. As far as the motor itself is concerned, lower voltage mostly means a lack of power at higher speeds, so even 1/4 of the stock 360 volts might be enough for the low power and probably less than 2000 rpm needed to substitute for the original engine. The biggest problem is likely that the inverter is designed for use with a battery which is never at less than 300 volts, so it might not even turn on - let alone work properly - at a significantly lower voltage.

This is an issue with the components from almost any EV. Batteries are all configured with modules in series so using a fraction of them means the same fraction of the stock voltage. 96 cells in series resulting in 360 volts (nominal) is nearly an industry standard; some EVs and plug-in hybrids use slightly lower voltage (e.g. a Mitsubishi Outlander PHEV is only 80S so 300 volts), but none are designed for anything close to 100 volts. That's industrial vehicle and do-it-yourself conversion kit territory.
 

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For a smaller pack than using a full EV pack, the plug-in hybrid batteries are smaller (simply because they have less energy capacity) and yet similar voltage. It might be possible to stack an entire set of modules from a Chevrolet Volt or Chrysler Pacifica Hybrid around and on top of the motor - although the original engine cover wouldn't cover them - for 360 volts. The Outlander PHEV modules are interesting, too, because they are air-cooled for simplicity.

With any battery configuration weight is going to be a concern. This tractor is too tail-heavy anyway due to the engine location (apparently nose counterweights are routinely used), and any motor plus any significant fraction of a typical EV battery pack will be even heavier and centred even further back. Is is possible to mount some battery modules somewhere further forward? The trick in existing conversions of this model of tractor seems to be stacking battery over the axle, rather than back over the motor, as much as possible.
 

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Discussion Starter #6 (Edited)
Thanks everyone for your input. It looks like using the Nissan leaf drivetrain is not feasible for the tractor given its small size. Does anyone have any recommendations for a motor/drivetrain and battery/bms configuration? I was hoping to use lithium batteries and could wire the motor and controller all together. The article from 2003 about converting an Allis Chalmers G was very helpful https://cdn.sare.org/wp-content/upl...tivating-tractor-into-an-electric-vehicle.pdf and references a motor but are there better options out there with newer technology? The original gas engine was only 10 hp and the top speed of the tractor is about 7 mph and the engine had rated rpm of 1800. I was potentially thinking of hooking up a raspberry pi and controlling the speed through a joystick as well
 

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For a tractor, you don't care about power. You care about torque. A 65 HP tractor, for example, is HUGE and 40HP will run a bush hog or pull a three furrow plow.

What you want is TORQUE. Since you probably want to keep the tractor's gearbox, that means coupling your electric engine-replacement to the input shaft of the transmission. You want to get the RPM as close to 1800 as possible, which means a gear reduction for most motors and, likely, coupling the axle drive to the input shaft of the tranny. Check the top speed of the donor car and then work backwards to get the wheel/halfshaft RPM.

For many vehicle donors, getting the torque you want
means turning the drive unit so the half shafts are longitudinal in the tractor, as well as jamming the differential (most do this by welding the spider gears), then coupling that to the tractor transmission. Not as horrible as it sounds. You want your gear reduction to ideally be from the peak horsepower part of the RPM curve, but you will likely be overpowering the tractor with most small car drive units, anyway, so being anal retentive about milking every ft-lb of torque is pointless.

I think a Leaf drive unit is major overkill, but you can always limit the output, I guess. You might want to look at a Smart Fortwo, or other pipsqueak EV. You can get a ForTwo with a dent in it for under 2 grand. Just make sure you can do 1800 RPM ***at the axles of the drive unit***, because that's the RPM implements are geared to run at. The motor in your leaf is so overkill, you *might* be able to direct drive it to the trans and have enough torque at 1800 without doing anything, now that I think about it.

If you're running a loader, rear-bias the batteries. If you're running implements, batteries go where the engine was if you don't want it to look too redneck. If you do both, there's nothing stopping you from moving the pack around, depending on what you're doing.

Unlike a car, a tractor runs at full rated power all the time it's working, so factor that into your cooling and current calcs..

Keep us posted here with a build log topic. As you can probably tell, I have a project lined up behind about a half dozen others to convert a farm tractor.

Have been down with severe Covid the past 6 weeks or so, so finishing one project would make me happy to have the chance to do at this point. Maybe I'll have a new sense of urgency when I'm clear of this calamity and my loss of part of a lung is not going to have me dragging an oxygen tank around (the part you don't hear about with "survivors"), though that could come in handy if I can find a cutting torch splitter.
 
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