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Discussion Starter · #1 ·
I'm considering converting my 924 to electric, mainly as I think it would be a good project and potentially make a cracking car?

My main concern is that electrics aren't really my thing, if anything, they are my weakness, especially if I have to try and work out how to wire something up!

I'm competent with greasy and oily things but, this is a big leap for me!

However, I am one of those people if I was told I needed to buy an A, B and C and then wire it up as per this youtube link - I'd be absolutely fine.

However, when it comes to fabrication, this isn't going to be a problem. My best mate who is also quite interested in this project is a professional welder/fabricator so I have access to all types materials and welding techniques.

I'm going to use my '86 924 S as the vehicle that will receive the final fit but, I have an '83 car minus the engine that I am going to use as a test bed to build everything on so I can keep my S on the road and running until I've got a sorted system and am ready to go!

I expect I may have expectations that are unrealistic but, I'd love a car that could do a minimum range of 100 miles and was comparatively as quick as the S (not that quick by modern standards!) but, using a fairly simple system - I read a lot about forklift truck motors being used (?) but, spending a good portion of my budget on buying a good battery pack -Tesla etc so hopefully my range would be realistic?

I'm planning on dumbing down my vehicle, electric windows and mirrors are going and anything else I can get rid of, I will - especially weight which I'm guessing has a direct impact on the range?

At this point in the infancy of my plan, I have a few major questions (for me).

1. My car is rear wheel drive, driven by a torque tube to a gear box at the rear. How much of the original drive train will I need to keep? Do I need a gearbox?

2. How do I mate the new electrics with the existing electrical system in my vehicle? Is it a simple process? Is there benefits to uprating my lighting to LED's to save power? Is there a simple way around having a heater in the vehicle?

3. What bits do I actually need to buy for the conversion? Is it better to buy a ready made kit (not really my thing - I prefer to fiddle!) or can I source everything I need from other (potentially) cheaper sources?

In essence, what do I need to rip out of my project car, what do I need to buy and, is there a wealth of diagrams and videos that will show me how to do the tricky bits?

Cheers in advance for any info!
 

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I'm considering converting my 924 to electric, mainly as I think it would be a good project and potentially make a cracking car?
Yes. And a moderately common one I think.

l receive the final fit but, I have an '83 car minus the engine that I am going to use as a test bed to build everything on so I can keep my S on the road and running until I've got a sorted system and am ready to go!
That's an excellent idea. Very convenient.

I read a lot about forklift truck motors being used (?) but, spending a good portion of my budget on buying a good battery pack -Tesla etc so hopefully my range would be realistic?
100 mile range is perfectly achievable on a cheap budget. You'll need a 25,000 kwh pack.

Tesla packs are expensive and performance oriented. Not your best bang for your buck.

I'm planning on dumbing down my vehicle, electric windows and mirrors are going and anything else I can get rid of, I will - especially weight which I'm guessing has a direct impact on the range?
Nope.

And why would you spend all this time converting a vehicle, so that you have a purposefully shittier vehicle to drive?

Weight has a minimal, almost trivial impact on range. Usually when people give rules of thumb for weight vs. range, it's based on the fact that heavier vehicles tend to be larger, and larger vehicles have higher wind resistance, and higher wind resistance is 90% of what costs you energy to keep moving through.

Weight has an impact on acceleration, which is mostly lost in braking (ignore regen, it has little impact), so if you're doing a ton of low speed starts and stops then your range is going to have a little more impact from weight, but otherwise, almost none.

If you can lighten the vehicle by say, half? Maybe go for it.

But to strip out useful features to save at most dozens of pounds? Never. I'd say it literally won't make 300 feet of difference to your range.

1. My car is rear wheel drive, driven by a torque tube to a gear box at the rear. How much of the original drive train will I need to keep? Do I need a gearbox?
Wheels, axles, diff - Keep for sure.

Driveshaft/Trans - Up to you.

A transmission is nice to have a physical disconnect in emergency. It also gives you a mechanical reverse (rather than electric reversing). Realistically you don't need a transmission. You have enough torque from zero, and it's a light car, you're probably fine. Just FYI, most EV conversions that leave the transmission just keep the car in 3rd gear all the time, even when starting, and occasionally slip into 4th gear on the highway. They might go weeks or months of daily use without shifting gears. You'll be a little less zippy off the line to kill the trans entirely, but you have more fitment options and less weight if you scratch it.

You'll have to add electric reverse (contactors to flip two big cables) without a trans. If you are doing a super, super cheap build you might want to save a few bucks on those by keeping the trans but, as soon as you're buying batteries the cost of penny pinching elsewhere goes out the window.

2. How do I mate the new electrics with the existing electrical system in my vehicle? Is it a simple process? Is there benefits to uprating my lighting to LED's to save power? Is there a simple way around having a heater in the vehicle?
You keep all your 12v electronics, probably even your starter battery just as a reserve. Then you just have a DC-DC converter to buck down from your pack voltage to 12v.

Take all the money you'd spend on LEDs and spend it on batteries.

Headlights are ~150 watts for the pair. Driving highway speed is 15,000 watts. So you'd see literally 1 mile of difference if you could remove the headlights entirely. Less if just converting to LED. Don't bother.

Simple way of having a heater? Use a plug in ceramic space heater from a thrift store. Or use something from a scrap EV. Or plumb waste heat from the speed controller.

3. What bits do I actually need to buy for the conversion? Is it better to buy a ready made kit (not really my thing - I prefer to fiddle!) or can I source everything I need from other (potentially) cheaper sources?
1 - Motor.
2 - Controller.
3 - Batteries.
4 - Vacuum pump to run the brakes.
5 - All the little bits and pieces unique to your build, wiring, connectors, etc.

You can buy something like a kit for 10x the cost and you'll still have to do a lot of custom work to it.

Motor will be nearly free. Controller you'll have to build or buy, $500-$1000. Batteries you'll have to buy (a few thousand).

This is very doable for someone with little or not electrical knowledge.
 

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Discussion Starter · #3 ·
Firstly, thanks for the info and the time taken to write it!

Re the transmission, I know this is probably a bit of an obvious question but, if I remove the gearbox and torque tube, I’m assuming that the electric motor will then be fitted somehow directly to the diff?
If so, I take it that it’s just a case of fabricating an adaptor plate to mate the two parts?
Re the reverse, it sounds simple enough to have a switch for reverse but, I’m not missing anything there am I? It’s just a case of flicking a switch and I’ll be going backwards?
If I have got things right and the motor was mounted at the rear, I suppose the obvious choice would to be to put the batteries up the front, somewhere in the void left by the engine - along with all the ‘new’ electrics?

I thought it would be a sensible option to go for the Tesla batteries as I was under the impression that they were the best available but, with regards to your comments, what battery system would you recommend?

I’m UK based but I although there will be some variation in EV models available here, I’m guessing a lot of manufacturers ‘share’ so I should be able to get something similar to your recommendations?

The controller. You mentioned making one - that sounds a little bit electrical and potentially difficult? Is it simple enough to do or should I save myself the pain and buy one?

Finally, before I go off and do more research, what motor would you recommend? If I’m being honest, I would like some performance but, I need to balance this against range. It’s pointless to have a road-rocket that only has a range of 30 miles but conversely, I don’t want to drive a slug for a 100 miles!!
I can start looking at motors now as I’m guessing that it’s going to be the first step, getting it mated up correctly.
 

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Re the transmission, I know this is probably a bit of an obvious question but, if I remove the gearbox and torque tube, I’m assuming that the electric motor will then be fitted somehow directly to the diff?
Depends on the suspension, of which I'm a novice at understanding so I can't be too specific.

You might need a pair of U-Joints to handle misalignment.

The bigger concern is whether you can actually fit a motor there, and whether the 924 has room, or you are okay with making room by modifying the underside of the body. And, perhaps clearance issues too. But if you can make it work it'd be a nice setup.

You could buy a replacement rear end from a salvaged OEM EV, but there's lots of fitment issues there too to troubleshoot. And it's probably out of your dollarstore budget.

If so, I take it that it’s just a case of fabricating an adaptor plate to mate the two parts?
That will be needed regardless of what you're mating to what. Brackets and mounts and things to hold things to other things.

Re the reverse, it sounds simple enough to have a switch for reverse but, I’m not missing anything there am I? It’s just a case of flicking a switch and I’ll be going backwards?
Electrically, it's very simple.

On a DC motor, all it's doing it taking positive and negative, and swapping places.

In order to do that, you need an electromechanical switch for each wire, which both switch at the same time. This is just a part you can buy, it's a Double-Throw-Double-Pole contactor (a contactor is a big relay). But to get one rated for big enough voltage and current is a bit expensive (high dozens of dollars at least).

To make the contactor toggle, you just control it with a small switch, anything will do.

If you want to go with a really ghetto setup, (as in, you want to save every dollar and do the bare minimum to make the vehicle functional at first), you could make your own switch from chunks of copper or a wallet-sized plug that you pull out and put back in backwards every time you want to change direction. You're (hopefully) never changing from forward to reverse and back when there's any power flowing, so, it's pretty simple in design. Depends on your priorities though.

If I have got things right and the motor was mounted at the rear, I suppose the obvious choice would to be to put the batteries up the front, somewhere in the void left by the engine - along with all the ‘new’ electrics?
It's a unique challenge to each vehicle. Generally yes. And, even if you (honestly, likely) mount the motor up front still, a motor is going to be way smaller than an engine, so, batteries will still probably go up front. Maybe a few more wherever the gas tank used to be. Under seats are another popular option. Wherever you can stuff them basically.

I thought it would be a sensible option to go for the Tesla batteries as I was under the impression that they were the best available but, with regards to your comments, what battery system would you recommend?
You have to go to a scrappers to have a chance at doing this affordably. And then the answer is, anything. Literally any OEM EV vehicle battery pack is fine for you. Form factor is probably something to consider (different models have different shapes and sizes that will be more or less suitable to you).

The controller. You mentioned making one - that sounds a little bit electrical and potentially difficult? Is it simple enough to do or should I save myself the pain and buy one?
You don't design one. You buy plans and follow instructions to build one, or a kit. (Or maybe find someone who built one but never finished their project). A DC power supply is pretty straight forward. If you can build a LEGO set and smoke a cigarette without lighting your eyeballs on fire, you are qualified.

Finally, before I go off and do more research, what motor would you recommend? If I’m being honest, I would like some performance but, I need to balance this against range.
A forklift motor. There's a gigantic thread stickied at the top of the Motor subforum.

Basically, chances are any old forklift motor you pull yourself is going to cost you a couple hundred bucks (scrap value), and you'll want to make sure it's roughly the right size (usually diameter is the lingo), with decent brushes, and, obviously the right type. You take a spare car battery and some jumper cables, maybe a chunk of wire with you to spin it up and test it. Most shops will have a shelf in the back of a few "just in case" motors but the other 99% of them get hauled off for scrap.

I can start looking at motors now as I’m guessing that it’s going to be the first step, getting it mated up correctly.
Yep. You're probably looking for something 11" in diameter. There's not a lot of variation. Chances are the first mid-sized junk forklift you see will have a suitable motor. If you're unlucky you might have to poke around 3 or 4.
 

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You'll need a way to charge the batteries, which involves a charger, a battery management system (BMS), controller(s) for them, and some display to tell you the state of charge and what not. Thunderstruck sells this stuff, as well as Orion. Total cost will likely run over $2k.

You'll want to keep your transmission, as a lot of these forklift/aftermarket electric motors have redlines of around 3,000 RPM (OEM motors spin much faster). The sticky wicket with the 924 is that the transmission is in the rear even though the motor is in the front. That's rare. I don't know how the engine couples with the torque tube, but it might just be similar to any other bellhousing.



All that said, you might want to look into ditching the whole transaxle and torque tube and putting something like a Nissan Leaf motor (with 8:1 reduction gear intact) in the rear. You would need custom axles, and a way to mount the motor to the car, but the rest is finding locations for the other components, and wiring more or less.

If I were you, I'd leave the rest of the car intact and unmodified as much as possible.
 

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Discussion Starter · #7 ·
To remove a few possible options to make the path slightly clearer, if I decide to start using axles etc from other EV vehicles, I’m probably going to fall foul of some of the registration legislation here in the UK regarding modifications and make my life exceptionally painful!

In light of this I will have to use the (major) components as fitted. This does in some way, clarify my path.

Re the 924 set up, yes, the torque tube essentially has a bell housing on that mates to the engine so, if it utilised the torque tube and gearbox, it wouldn’t be too much of an issue to mount the motor at the front.

I’ve had a look on eBay today at electric forklift motors and there seem to be only a few for sale (maybe I just searched on the wrong day?) but, loads were available from the U.S.
Maybe we do forklifting differently here?! Apparently most of them run on LPG?

Anyway, I found a reconditioned one with the following spec. It it the sort of thing I should be looking at?

Motor Specs

Power 5KW

Voltage 48v fed from a logic controller

Current 157A

Rated speed 1500 rpm

Maximum speed 4500 rpm

Frequency 75 Hz

Cos 0.72

Service S2 60

Insulation class F

Protective Degree IP10

Bearings 6206 2RS

weight 38.5kg

As ever, many thanks for your help!!
 

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As I suspect you now understand, there is no way to remove the transmission without removing the differential (because they are both within the transaxle), so connecting a motor directly to the original differential is not an option.

It would be beneficial to keep the motor out of the engine compartment, because you need space for battery and the motor both takes space and is heavy. If the entire transaxle is retained, but the torque tube is removed, it would be great to put the motor directly on the from of the transaxle; unfortunately, there isn't enough space for a motor (especially those old "forklift" brushed DC motors) between the transaxle and the torsion bar housing of the rear suspension.

For more discussion of 924 configuration options, I suggest reading the other recent 924 discussion in this forum.
https://www.diyelectriccar.com/forums/showthread.php/showthread.php?t=201041&amp=1
 

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Matt's suggested battery capacity of "24,000 kWh" was, of course, supposed to be just 24 kWh, or 24,000 Wh. For perspective, this is the capacity of an early Nissan Leaf pack; new production EVs tend to have 40 kWh or larger capacity.
 

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I think you will find the other post you referred to is the same OP just trying to move the discussion to an appropriate section of the forum
 

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I’m not sure you could not fit a motor onto the transaxle. I’m pretty intimate back there on 924’s and you will have to support the transaxle once you remove the torque tube. Depending on if you intend to keep the non functional rear seats you may find a slight rotation in the transaxle will accommodate the forklift motor. It’s not a route I chose so I never thought about measuring up for that but there is a fair amount of room and a plate to a transaxle that already has a spline coupler is a rare treat.
 

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I think you will find the other post you referred to is the same OP just trying to move the discussion to an appropriate section of the forum
LOL
I didn't check the member name, because the questions seemed like they were from someone who had not been in the previous discussion.
 

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I’m not sure you could not fit a motor onto the transaxle. I’m pretty intimate back there on 924’s and you will have to support the transaxle once you remove the torque tube.
I (still) agree with the space concern.

One way to address the support issue is to replace the torque tube with a beam (all the way to the battery box structure, or to a convenient intermediate location). The situation is similar to the Miata, which has a Power Plant Frame performing this function.
 

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Discussion Starter · #15 ·
I’ve tracked a breakers down who have a few motors available and I’m going to give them a call tomorrow and hopefully, finally get my hands on a motor!

However, I don’t really know what I’m talking about - what do I need to ask?

Everyone seems to mention the size - 11” motor etc and I’m guessing I want a 48v DC but when it comes to the max rpm, do I need a certain or, minimum rpm speed?
 

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Everyone seems to mention the size - 11” motor etc and I’m guessing I want a 48v DC but when it comes to the max rpm, do I need a certain or, minimum rpm speed?
Knowing the context of where they were used, you're probably fine to just pick a general motor. The specs are going to be in the same ballpark.

What you want to look for are brushes and a commutator in good shape.

You'll want 4 terminals accessible. You'll want it to be a series-wound motor.

Show up with a spare car battery and some jumper cables, and a jumper wire (to connect between coils that your jumper cables aren't on). Make sure it spins. If it squeels, not a big deal, you'll want new bearings anyways and a bearing set is $20.
 

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If I were you, I would use one of the new Netgain Hyper 9 AC motors.
This will give you regen and especially no brushes to wear out.

These come as kit complete with controller, meter, foot pedal, contactor and LV wiring.

It would be a lot more expensive that a fork lift motor, but much better in the long run.

Simple replace the ICE with the AC motor, leaving the rest in place.
 

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If I were you, I would use one of the new Netgain Hyper 9 AC motors.
This will give you regen and especially no brushes to wear out.

These come as kit complete with controller, meter, foot pedal, contactor and LV wiring.

It would be a lot more expensive that a fork lift motor, but much better in the long run.

Simple replace the ICE with the AC motor, leaving the rest in place.
A Porsche with a wimpy Hyper 9 - !!!
 
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