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Discussion Starter · #1 ·
Hello, all -- been reading these forums for over a year trying to learn the ins and outs of EV conversions.

My obsession is with building a first gen Bronco EV conversion, a few have been done by high dollar custom shops but none well-documented.

If money were no object I'd do a model 3 motor and torque box, with as many tesla batteries as I could make room for, I think. Sadly, I don't have 20k to spend on motor/drivetrain/controller.

I wondering what the consensus is on a hyper9 + torquebox, as far as power goes? I'm not an off-roader, so I'd ditch 4WD, and really I'm just looking for a fun cruiser on Tennessee's windy state highways. 200 mile range would be delightful but 150 would honestly work fine too. I feel like the hyper9 stats are pretty close to the original 302 motor, except the hyper9 will make that power basically from 0-4800rpm rather than just in one narrow power band. But the bronc does have a curb weight of 4500lbs, so maybe I'm wrong on that.
 

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I don't understand "Model 3 Motor and a Torquebox".

Why Tesla batteries?

Why do you need so much range when you plug in every night at home? Do you have such mad skills that you are confident you won't break down 500 miles grom home in a car nobody will touch for repairs (meaning a $500 tow home)?

Why ditch the 4WD which is the heart of the beast?

Is it a stick, 3 in the tree, or auto trans?

What kind of grades are on these TN roads?
 

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I wondering what the consensus is on a hyper9 + torquebox, as far as power goes? I'm not an off-roader, so I'd ditch 4WD, and really I'm just looking for a fun cruiser on Tennessee's windy state highways. 200 mile range would be delightful but 150 would honestly work fine too. I feel like the hyper9 stats are pretty close to the original 302 motor, except the hyper9 will make that power basically from 0-4800rpm rather than just in one narrow power band.
No, the HyPer9 will not make rated power at any speed under 3600 RPM (std version) or 4000 RPM (HV version), because below that point it is current (and therefore torque) limited. According to NetGain's published charts, full power is available over roughly 4000 to 5500 RPM (either version).

The 1969 Bronco 302 was rated at 153 kW gross; testing at the time didn't include net output, but it would certainly be more than the 90 kW of a HyPer 9. Performance with the HyPer 9 and appropriate shifting might still be acceptable.
 

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Discussion Starter · #4 ·
No, the HyPer9 will not make rated power at any speed under 3600 RPM (std version) or 4000 RPM (HV version), because below that point it is current (and therefore torque) limited. According to NetGain's published charts, full power is available over roughly 4000 to 5500 RPM (either version).
Wait, really? I'm looking here (https://www.go-ev.com/PDFs/HyPer_9_132V_Performance.pdf) and it seems to indicate torque values are steady/maxed from 0RPM to ~4500RPM. Is there another chart I should be using instead?

The 1969 Bronco 302 was rated at 153 kW gross; testing at the time didn't include net output, but it would certainly be more than the 90 kW of a HyPer 9. Performance with the HyPer 9 and appropriate shifting might still be acceptable.
I have a buddy who's dyno'ed his early bronco with original 302 and, as you would expect, it made barely 120hp during a very narrow powerband. Those 302's just didn't breathe all that well, I guess. That's what led me to wonder if a similarly sized electric motor could match or exceed that stock performance if I'm not trying to climb mountains or drag race.
 

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Discussion Starter · #5 ·
Why Tesla batteries?
Energy density and availability. Why not Tesla batteries?

Why do you need so much range when you plug in every night at home? Do you have such mad skills that you are confident you won't break down 500 miles grom home in a car nobody will touch for repairs (meaning a $500 tow home)?
I don't recall saying I needed that range. And I definitely never used the number "500 miles", so I'm not sure where you got that one from. 150-200 is what was in my post. 500 is considerably more than 150-200, if I remember my counting correctly. Your response reads as though you're annoyed with what was to me a very typical request for information from someone pondering a build. When you register for the forum you're instructed to post in this sub and ask questions about what you're wanting to do, which is exactly what I did. If there's something about that that has annoyed you it would be helpful to a new poster such as myself if you'd explain why rather than posting something snarky.

Why ditch the 4WD which is the heart of the beast?
Initially I was thinking it would save weight and mechanical complexity, since I wouldn't need a 4WD vehicle. But looking at what it would take to ditch it it actually seems as though that would actually be way more work than just using the existing transfer case and keeping it. So for the moment I've dropped that idea.

Is it a stick, 3 in the tree, or auto trans?
It doesn't exist right now, so I'm happy to hear suggestions one way or the other. My preference is not to re-use a transmission, but to spend more money on a motor and gearbox that would allow me to ditch that. I know the standard conversion suggestion is to re-use the tranny so that you can open up a wider variety of motors, but I'd love to save the weight and space if there are some feasible ways to do that. I've seen a few options, but they're spendy. Personally, I don't mind sourcing the bronco, getting body and frame nice, and driving it with the original bits and pieces for a year or two while I finalize exactly what type of conversion I want to do. I expect that the longer I am willing to wait the more options we'll see for bolt on conversion parts.

What kind of grades are on these TN roads?
I'm in central TN, which is hilly compared to, say, Kansas, but not compared to the Smokies in east TN. We're not hill climbing here.
 

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For 150 miles of range in a Bronco you will need minimum 100kwh I'm guessing based on my experience with my Land Cruiser. Not sure where you would fit that. That would probably be 800-1000lbs just for the battery cells themselves. Others have done small 4x4s usually they put batteries both up front and in the back.

The TorqueBox is an attractive option because it has just a normal driveshaft yoke which would be pretty easy to adapt to your rear end differential if you don't desire 4WD.

Also Kansas is very hilly.
 

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Discussion Starter · #7 ·
For 150 miles of range in a Bronco you will need minimum 100kwh I'm guessing based on my experience with my Land Cruiser. Not sure where you would fit that. That would probably be 800-1000lbs just for the battery cells themselves. Others have done small 4x4s usually they put batteries both up front and in the back.

The TorqueBox is an attractive option because it has just a normal driveshaft yoke which would be pretty easy to adapt to your rear end differential if you don't desire 4WD.

Also Kansas is very hilly.
Cool, that's good to know! 100kW-hr is about what I'd calculated for batteries, and front, back, and underneath was the tentative plan for locating them.

What're you using as your motor? I've seen Land Cruiser conversions running the Hyper9, but I'm hearing in this thread that that's way under-powered.
 

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Discussion Starter · #8 ·
Wait, really? I'm looking here (https://www.go-ev.com/PDFs/HyPer_9_132V_Performance.pdf) and it seems to indicate torque values are steady/maxed from 0RPM to ~4500RPM. Is there another chart I should be using instead?



I have a buddy who's dyno'ed his early bronco with original 302 and, as you would expect, it made barely 120hp during a very narrow powerband. Those 302's just didn't breathe all that well, I guess. That's what led me to wonder if a similarly sized electric motor could match or exceed that stock performance if I'm not trying to climb mountains or drag race.
@brian_ if you get a chance, I'd love to make sure I'm not looking at the wrong torque values for the Hyper9, because all I can find is what I linked above.
 

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Wait, really? I'm looking here (https://www.go-ev.com/PDFs/HyPer_9_132V_Performance.pdf) and it seems to indicate torque values are steady/maxed from 0RPM to ~4500RPM. Is there another chart I should be using instead?
No, there isn't a better source, but the torque on that graph is in blue, and drops off after 3600 RPM.

Because power is torque multiplied by speed, power rises in proportion to speed from zero at zero speed to until the torque starts dropping off, and doesn't reach its peak value until over 5,000 RPM.

@brian_ if you get a chance, I'd love to make sure I'm not looking at the wrong torque values for the Hyper9, because all I can find is what I linked above.
Those charts from NetGain are all that is really available... but note that there are different versions for regular and high-voltage motors, and with different supply voltages, and all are limited by the current limit of the controller used for testing.
 

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Discussion Starter · #10 ·
No, there isn't a better source, but the torque on that graph is in blue, and drops off after 3600 RPM.

Because power is torque multiplied by speed, power rises in proportion to speed from zero at zero speed to until the torque starts dropping off, and doesn't reach its peak value until over 5,000 RPM.


Those charts from NetGain are all that is really available... but note that there are different versions for regular and high-voltage motors, and with different supply voltages, and all are limited by the current limit of the controller used for testing.
Torque is what I was looking at. I think my confusion was your claim that the hyper9 is torque limited until 3600RPMs, which isn't what that chart shows. It shows constant torque until 3600RPMs, with a slight drop-off to 5000RPMs, and pretty steep beyond 5000.

I hear what you're saying about not making peak power until 3600RPMs, although power isn't torque * speed but rather torque * Vrms (as long as we're nitpicking let's do it all the way), so that's actually not a big deal to me. I was mistaken to say the motor will provide rated power through the RPM range -- what I should've said is it'll provide rated torque through that range, which it will, and torque is also the thing I care about as opposed to peak power.

I know the claim is that the bronco 302 would produce 150kW, but as I said I've got a friend who dyno'd his 302 early bronco and he got 120hp peak, which is 90kW, which is dead on what a Hyper9 will do. And with a hyper9 offering much better low speed torque through that peak power, I just keep staring at it wondering it it's workable.

Which, full disclosure, is largely motivated by how affordable it is compared to larger motors and controllers.

I appreciate the education!

I saw an EV bronco yesterday at SuperCell in TN, and it's got a stealth drive, which they don't seem thrilled with. Rather have an underpowered conversion with a 5k motor than with a 20k one, I guess is my thought process.
 

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I'm using a Nissan Leaf motor and just about everything else too. You can search my thread on here. I'm limited to 160kw if I swap an inverter but no more which is the only downside of my Leaf/Resolve-EV path.

If you don't drive off-road you can mount a Tesla drivetrain sideways and get RWD (with a spool) or AWD.

See this video at 10:38 for an example:
 

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Discussion Starter · #12 ·
I'm using a Nissan Leaf motor and just about everything else too. You can search my thread on here. I'm limited to 160kw if I swap an inverter but no more which is the only downside of my Leaf/Resolve-EV path.

If you don't drive off-road you can mount a Tesla drivetrain sideways and get RWD (with a spool) or AWD.

See this video at 10:38 for an example:
Nice! Yeah, I've looked at that tesla LDU longitudinal install in the trans-tunnel, but I'm worried that the bronco driveshafts aren't offset, so I'm not sure how easy it would be to adapt driveshafts for them. But I love that idea.

The leaf setup isn't one I've looked too hard at, I'm gonna read your build thread and get some inspiration. Thanks!
 

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Torque is what I was looking at. I think my confusion was your claim that the hyper9 is torque limited until 3600RPMs, which isn't what that chart shows. It shows constant torque until 3600RPMs...
Aren't those the same statement? From zero until 3600 RPM, the performance of the motor is limited by torque - it can't produce more power because it can't produce more torque.

I hear what you're saying about not making peak power until 3600RPMs, although power isn't torque * speed but rather torque * Vrms (as long as we're nitpicking let's do it all the way)...
No, combining the mechanical measurement of torque with the electrical measurement of voltage isn't useful.
  • Mechanical power output of the motor is the product of shaft torque and shaft speed.
  • Electrical power input to the motor is the product of current and voltage (yes, in RMS values of amps and volts, multiplied by power factor, for each phase, and accumulated across all phases if you want to be more precise).
  • Often in EVs motor current and voltage are not mentioned at all, since the motor and controller-inverter are considered as one "black box" system. Electrical power input to the motor-inverter system is the product of current and voltage from the DC link to the battery; they're just DC, so the amp and volt values are simply multiplied.
In an electric motor at low speed and moderate current, torque is approximately proportional to current, so they are certainly related, but they're not the same thing.
In an electric motor in an operating region not limited in current and with constant rotor magnetic field strength, the voltage required to overcome back EMF is proportional to speed (for a given stator current and therefore stator field)... so voltage is related to speed, but they're not the same thing.

I was mistaken to say the motor will provide rated power through the RPM range -- what I should've said is it'll provide rated torque through that range, which it will, and torque is also the thing I care about as opposed to peak power.
But the rated torque is not provided through the motor's whole RPM range, unless you restrict it to never running faste than 3600 RPM so it doesn't.

Torque by itself doesn't matter. You can put a breaker bar on a wrench and apply a thousand pound-feet of torque to a stationary shaft, but that doesn't make you capable of driving that shaft like an engine that can produce a thousand pound-feet of torque at a couple thousand RPM. The engine of a 60-ton Abrams M1 tank can only produce 279 lb-ft of torque, but it moves the tank very capably because it delivers that torque at 30,000 RPM. A 10:1 reduction gear set integrated with the engine makes that into 2768 lb-ft @ 3,000 RPM to feed to the transmission, which makes it into far more torque at far lower speed to drive the tracks. Torque is only meaningful to performance with the corresponding speed.

I know the claim is that the bronco 302 would produce 150kW, but as I said I've got a friend who dyno'd his 302 early bronco and he got 120hp peak, which is 90kW, which is dead on what a Hyper9 will do. And with a hyper9 offering much better low speed torque through that peak power, I just keep staring at it wondering it it's workable.

Which, full disclosure, is largely motivated by how affordable it is compared to larger motors and controllers.
That makes sense to me.

Except that the motor's peak torque (up to 3600 RPM) and the motors peak power (at around 5000 RPM) are choices - you can't have both at the same time.

And except that the dyno test would likely have been on a chassis dyno, measuring power after all losses in the transmission, driveline, and most importantly tires. The stock engine power rating and the electric motor power rating are at the motor output shaft.
 

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Discussion Starter · #15 ·
Torque by itself doesn't matter. You can put a breaker bar on a wrench and apply a thousand pound-feet of torque to a stationary shaft, but that doesn't make you capable of driving that shaft like an engine that can produce a thousand pound-feet of torque at a couple thousand RPM. The engine of a 60-ton Abrams M1 tank can only produce 279 lb-ft of torque, but it moves the tank very capably because it delivers that torque at 30,000 RPM. A 10:1 reduction gear set integrated with the engine makes that into 2768 lb-ft @ 3,000 RPM to feed to the transmission, which makes it into far more torque at far lower speed to drive the tracks. Torque is only meaningful to performance with the corresponding speed.
That's a very helpful way to mentally model what's happening here, much appreciated for sharing it. :)
 
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