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Discussion Starter · #1 · (Edited)
For 6 years now I've owned, daily-driven and constantly maintained a 1985 Jeep CJ7. Several years ago I swapped in a 4.0 from a '98 Grand Cherokee but would like to some day convert to electric if I'm able to meet my needs.

I've read around on here and many other websites off and on over the past couple of years, trying to figure out if it would work and what it would cost. With so many various options, opinions and versions, I would just get lost in the mix and give up for a while.

I'm not getting into the specifics and exact parts of an EV right now, just trying to figure out if my dream is possible and/or makes sense both physically and financially.

What I have:
- 4.0 HP: 185hp @ 4600 rpm / 75hp @ 2100 for 60 mph highway cruising
- 4.0 Torque: 230ft-lbs @ 2400 rpm / 224ft-lbs @ 2100 for 60 mph highway cruising. Torque decreases as rpm increase with this engine.
- Curb Weight: 2,800 lbs
- 0-60 in 9 to 10 seconds
- 4x4 part time. Permanent rear, front engaged manually, disconnect at both transfer case and wheel hubs.
- Manual Brakes
- Power Steering
- 33 inch tires that are actually 32 inch. Spin 2100 rpm at 60 mph highway driving.
- Brick aerodynamics however I am an easy driver averaging 19 mpg GPS certified which is very rare with this vehicle.
- Majority of lights, including headlights, are LED.


What I need after conversion:
- Same engine/motor specs. Not looking for increase or decrease. Never have gotten above 3500 rpm = 130hp when accelerating.
- Range capacity: 24 mile commute + 24 mile round-trip job/client visit + 20% contingency (?) = 58-60 miles
- 16 miles of commute + 16 miles of visit distance is highway cruising at around 60 mph. Rest is around 40-45 mph start & stop.
- retain 4x4 capabilities for jobsite visits
- retain manual brakes
- retain power steering
- drive with lights on for safety
- ability to do 70 mph for about 8 miles of rare Interstate traveling.
- retain 9-10 sec for 0-60 mph capability for getting on interstates & highways in rare circumstances. 13-20 sec normally.
- Want to keep all 4 seats for short family trips on weekends.
- Thinking might only have battery space at old gas tank location & misc area around motor under hood.

So is this possible or asking too much? I know enough money will buy me what I want but within common sense, are my wants obtainable?

I'm a big time newb, so please be easy on me! From what I've read I do know that I want an AC system and regenerative braking. I do know that my driving style will be completely different. Just please remember that for right now, I'm trying to look at the forest as a whole instead of the individual trees so I know if I'm wasting my time and should stop dreaming/wondering.

I've tried to look up other Jeep/4x4 conversions to see what they did, what it cost and how they perform but they were all so different from mine. They wouldn't retain 4x4, wouldn't drive over 45mph or only used it for offroading or rock crawling so I thought I'd post.

Thank you!
Neuner
 

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I've tried to look up other Jeep/4x4 conversions to see what they did, what it cost and how they perform but they were all so different from mine. They wouldn't retain 4x4, wouldn't drive over 45mph or only used it for offroading or rock crawling so I thought I'd post.
Welcome to the forum :)

I'd recommend you give Anne at New Electric a call (here)... he can answer your questions and the jeep they converted is amazing :cool:
 

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I think your expectations are pretty good and quite well articulated (rare thing on these forums).

The only thing I would mention is that in EV terms you don't need quite the same power to achieve the same performance. The higher torque and flat power curve compensates for a lower peak power figure.

It is difficult to predict what exact power to aim for to achieve the same performance. Torque is what gives most of the acceleration. Power gives you speed. So given that you only aim to do highway speeds I would recommend focusing more on the torque characteristics and a little less on the power characteristics. Take a look at the figures quote for similar sized vehicles in the Garage list. It will give some clues for what to aim for.
 

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Discussion Starter · #4 ·
I'd recommend you give Anne at New Electric a call (here)... he can answer your questions and the jeep they converted is amazing :cool:
Thanks, but I'm in the U.S.

The only thing I would mention is that in EV terms you don't need quite the same power to achieve the same performance. The higher torque and flat power curve compensates for a lower peak power figure.

It is difficult to predict what exact power to aim for to achieve the same performance.
Correct and why I was looking at charts and plots of my engine's power curve. For an ICE, the Jeep 4.0 is a torque monster. It starts off around 240 ft-lbs at low/idle rpm and goes down from there as rpm increases so during my normal driving, I'm almost at it's max.

As I have noted above, according to the power graph, I should be at around 75hp at 2100-2400 rpm so I don't think I'd need more than this?
 

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For an ICE, the Jeep 4.0 is a torque monster. It starts off around 240 ft-lbs at low/idle rpm and goes down from there as rpm increases...
That's extremely unlikely, and a bit of research confirms that isn't true. Just look at any published torque curve for the 4.0 (from a real engine dyno) and you'll see torque climbing to about 3000 rpm (which is five times idle speed). However, this engine can put out substantial torque over a wide speed range.

As I have noted above, according to the power graph, I should be at around 75hp at 2100-2400 rpm so I don't think I'd need more than this?
Keep in mind that just as the engine's available torque and power depend on speed, so does the available output of the electric motor. A high-voltage AC PM or induction motor will have roughly constant torque output up to a transition speed (so it reaches 75 hp at that speed there will be only 38 hp available at half that speed), and then constant power above that; the power output of lower-voltage motors in typical DIY EVs drops off (sometimes dramatically) with increasing speed.

If you retain a multi-speed transmission you can work around the speed limitations; if you eliminate the opportunity to shift you need that peak power over a broad speed range (like production EV motors with their 360 volt batteries), or a higher peak power so you can accelerate at off-peak motor speed.
 

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Discussion Starter · #6 · (Edited)
That's extremely unlikely, and a bit of research confirms that isn't true. Just look at any published torque curve for the 4.0 (from a real engine dyno) and you'll see torque climbing to about 3000 rpm (which is five times idle speed). However, this engine can put out substantial torque over a wide speed range.
You're assuming that my 4.0 is stock and follows such graphs..... :D. BTW, not all 4.0s are created equal and a general search of the engine is like doing a general search on a 350. Just not the right thing to do. I'd post the graph I have from a build I copied but it's not allowing me to upload it for some reason. Think it's corrupted because I can't even load it into photoshop to resize it.

Keep in mind that just as the engine's available torque and power depend on speed, so does the available output of the electric motor. A high-voltage AC PM or induction motor will have roughly constant torque output up to a transition speed (so it reaches 75 hp at that speed there will be only 38 hp available at half that speed), and then constant power above that; the power output of lower-voltage motors in typical DIY EVs drops off (sometimes dramatically) with increasing speed.

If you retain a multi-speed transmission you can work around the speed limitations; if you eliminate the opportunity to shift you need that peak power over a broad speed range (like production EV motors with their 360 volt batteries), or a higher peak power so you can accelerate at off-peak motor speed.
Sort of lost me there but that's fine. Not looking for further explanation yet. Not until I decide to get into further details. I'm a visual learner so I'd probably have to see it in some sort of graph to understand and remember. You did answer a question of mine though as to whether or not I'd have to or want to retain the tranny. If I get the gist of what you're saying, I'll definitely want to keep it even with the negatives.

That's the other part that I haven't found much on. If anyone has a tranny with their conversion and how they drive it. Do they find one of the gears to be the right match for their setup and leave it in that gear full time or do they up-shift and down-shift like they did before?
 

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I'm a visual learner so I'd probably have to see it in some sort of graph to understand and remember.
Most brushed DC motor manufacturers appear to be afraid of publishing usable power and torque curves.
Power and torque curves for decent AC motors but at modest voltage:

HPEVS AC-51 (induction)


NetGain/ Hyper9 (PM)
 

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Transmission or not

You did answer a question of mine though as to whether or not I'd have to or want to retain the tranny. If I get the gist of what you're saying, I'll definitely want to keep it even with the negatives.
... unless you use a modern motor such as one from a production EV (Tesla and Leaf are the popular choices) and run it from a battery at or near the design voltage (typically 360 V or so, not the 120 V of common DIY EVs).
 

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Discussion Starter · #9 ·
Thank you! Those help a lot.

I was thinking about a salvaged Leaf after just recently reading more about it on a Land Rover conversion. Seems like the best way to go. Have everything you need in one package for relatively cheap in comparison and able to just stack batteries for your needs.
 

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Discussion Starter · #11 ·
Yes, thank you, I saw that on the latest LR post. Problem is that, as usual, I can't find any real world info about it, only a quick clip. Is it direct drive? Did he have it floored in the video? If so, then it's substantially weaker than what I have and need. Does he have a transmission and what gear was he in?
 

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Discussion Starter · #12 ·
With this possibly being more of a PITA than what I'm expecting, I have been keeping my eye open for the Bollinger if it ever gets produced, http://bollingermotors.com/. Not DIY but the concept is very cool and any repairs, updates or improvements are intended to be very DIY.
 

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Yes, thank you, I saw that on the latest LR post. Problem is that, as usual, I can't find any real world info about it, only a quick clip. Is it direct drive? Did he have it floored in the video? If so, then it's substantially weaker than what I have and need. Does he have a transmission and what gear was he in?
Mike is on DIY Electric but rather busy with his growing company... try leaving him a PM (here).
 

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Discussion Starter · #15 ·
this is an old post now, but i am just finishing a very similar project, using an ac-51 in cj-5: http://www.evalbum.com/preview.php?vid=5432
Thanks for sharing! That is exactly what I want to do. I even have the solar array for our home as well. If you don't want to share the cost, would you mind PMing it to me? It's my go/no-go decision right now.
 

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I was thinking about a CJ/Bronco conversion myself:

https://www.diyelectriccar.com/forums/showthread.php/planning-early-bronco-conversion-199747.html

The simplest solution for you would seem to be to keep everything from the transmission back. This would keep 4WD, provide wicked rock crawling torque, and allow for highway speeds with most motors. There are adapter bellhousings for the "Warp 9" pattern, and I think someone adapted a Leaf motor to the Warp 9 pattern...It's all pretty custom stuff.

The tricky bits would be mating the motor to the transmission, as well as the output shaft. Then you just need to find homes for the batteries and components and wire everything up. Be aware that almost nothing in a CJ keeps water out...

The Leaf sure seems to be the bang-for-buck champ for components at the moment (particularly if battery weight/volume aren't much concern), and there are some aftermarket alternatives if you only want to use the battery or motors. I'm attempting this with my own conversion, but I still haven't quite gotten the motor spinning outside of the car yet...If you buy a wreck, I think it's worth getting a wreck that can still drive under its own power. Then you'll know if there are problems, it's not the components, it's something else...

https://www.diyelectriccar.com/forums/showthread.php/nissan-leaf-into-rover-mini-129310-200007.html
 
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