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Discussion Starter #1
Hi, if I wanted to convert a 600-700kg road car to be fully electric, is there an off-the-shelf powertrain that I could consider other than using Tesla components? A previous suggestion focussed on:

1 x Tesla Rear SDU (Small Drive Unit)
12 x Tesla Battery Modules
1 x Tesla DCDC
1 x Orion BMS
1 x Tesla Gen 2 Charger
1 x Junction Box

This would produce around 300bhp and a top speed of ~150mph, apparently...

Any help or advice would be gratefully received!
 

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Hi, if I wanted to convert a 600-700kg road car to be fully electric, is there an off-the-shelf powertrain that I could consider other than using Tesla components? A previous suggestion focussed on:



1 x Tesla Rear SDU (Small Drive Unit)

12 x Tesla Battery Modules

1 x Tesla DCDC

1 x Orion BMS

1 x Tesla Gen 2 Charger

1 x Junction Box



This would produce around 300bhp and a top speed of ~150mph, apparently...



Any help or advice would be gratefully received!
What is your goal? Those components would be both very expensive and way overkill, most likely...

That's almost 700lbs of lithium batteries in a car that weighs almost 1,600lbs. 64 kWh is a big pack, too.

Let's work backwards from your requirements to design a system instead. You'll get a better car. Are you building a drag car? Daily driver? Etc.

Sent from my SM-N960U using Tapatalk
 

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Discussion Starter #3
Hi, if I wanted to convert a 600-700kg road car to be fully electric, is there an off-the-shelf powertrain that I could consider other than using Tesla components? A previous suggestion focussed on:



1 x Tesla Rear SDU (Small Drive Unit)

12 x Tesla Battery Modules

1 x Tesla DCDC

1 x Orion BMS

1 x Tesla Gen 2 Charger

1 x Junction Box



This would produce around 300bhp and a top speed of ~150mph, apparently...



Any help or advice would be gratefully received!
What is your goal? Those components would be both very expensive and way overkill, most likely...

That's almost 700lbs of lithium batteries in a car that weighs almost 1,600lbs. 64 kWh is a big pack, too.

Let's work backwards from your requirements to design a system instead. You'll get a better car. Are you building a drag car? Daily driver? Etc.

Sent from my SM-N960U using Tapatalk
Hi jbman, thank you for your reply. I thought as much regarding weight, cost and power. So, I am basically looking to convert a small mid-engined kit car from ICE to EV. The objective is to build a unique hillclimb/track car for personal use. However, this does not mean that I’m happy to compromise on quality. So, I’m looking to keep the vehicle under 800kg (ideally), top speed of around 150mph, 0-60mph of 3-4 seconds and to have a range of 100-150 miles. I’d also like the charging system to be onboard...

Does this sound possible or more like fantasy?!?
 

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So, I am basically looking to convert a small mid-engined kit car from ICE to EV.
Since the car is mid-engined, it already has the engine and transaxle together, so they could be replaced by a typical EV "drive unit" (consisting of motor and transaxle) without having to adapt a motor to a transmission. The Tesla drive unit is an example of this.

The big problem is also fitting in a huge and massive battery pack.

If you take this approach, when selecting between the many EV drive units, here are some factors to consider:
  • most EVs are front wheel drive, but their drive units could be placed at the rear
  • essentially all drive units place the motor transversely, so they are configured with the transaxle much like a common transverse engine configuration in a front wheel drive car (and some mid-engine cars); however, the motor can be in different positions (ahead of, on, or behind the axle line), which changes how the unit packages into the car
  • the shape and position of the drive unit will affect how it fits with the car's rear suspension... and so whether you can keep that suspension or change it
  • the peak power output of a production EV motor could be much higher than the stock value if a modified or alternative controller is used
What engine, transaxle, and rear suspension does this car use? The small details don't matter - I'm just wondering about the size and position of the components. A "small mid-engined kit car" could use a transverse 4-cylinder engine from a production car, or a longitudinal engine on a transaxle that extends rearward (like classic formula cars and most mid-engine exotic road cars), or even some other unusual arrangement.

The objective is to build a unique hillclimb/track car for personal use.
...
I’d also like the charging system to be onboard...
Essentially all EVs include an on-board charger, which can be salvaged from a production EV, such as the Tesla charger that you listed. On the other hand, if this is a competition car, is it also intended to roadworthy? If it must be transported to events on a trailer anyway, I wouldn't want to carry the charger in the car, especially when targeting very low weight; it can just go with all the rest of the tools and supplies.
 

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... I’m looking to keep the vehicle under 800kg (ideally), top speed of around 150mph, 0-60mph of 3-4 seconds and to have a range of 100-150 miles. I’d also like the charging system to be onboard...

Does this sound possible or more like fantasy?!?
That sounds very optimistic to me. For the mass, I think it would make sense to do some simple calculations:
  1. start with the current mass
  2. subtract the mass of the engine, transmission, exhaust system, and fuel tank
  3. add the mass of all of the EV components
    • motor
    • controller
    • transaxle
    • battery, with cables and housings
    • charger
    • other electrical devices (contactors, etc)
What do you get? You are wanting to do this with a mass increase of only 100- 200 kg, but with the very large battery planned I don't think that will be possible.

A major variable is the battery. You need it to be large enough to have the energy capacity required to reach the range (or endurance, in racing terms) target. Even if you needed minimal range, it needs to be large enough to deliver the power required for your performance target.

The target weight of the Tesla Powered Cobra Race Car in this forum was 1800 pounds (816 kg) with a 30 kWh Kia Soul EV battery; I didn't search the whole thread for the final weight with the original battery pack, or the later upgrade to a 40 kWh Nissan Leaf battery. This vehicle is very similar to this project, in size, construction, and intended use - even using a Tesla drive unit - but is carrying much less battery than 12 Tesla Model S/X modules.
 

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Hi
The problem with your requirements is the range

My "device" is 800 kg with over 300 hp - but less than 40 miles range - quadrupling the range would add over 300 kg

Do an analysis on your driving - I found that I either drove for less than 40 km OR over 150 km
 

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Discussion Starter #7
Hi
The problem with your requirements is the range

My "device" is 800 kg with over 300 hp - but less than 40 miles range - quadrupling the range would add over 300 kg

Do an analysis on your driving - I found that I either drove for less than 40 km OR over 150 km
Hi Duncan, thank you for your reply. The car doesn't necessarily require 300bhp. I simply need enough power to deliver a top speed of 125mph+ and 0-60mph of 3-4 seconds, ideally. I guess a range of around 50km would suffice for hillclimbs and track days as you could recharge the batteries between runs. I'm just thinking about future-proofing the design in case I ever did wish to make it roadworthy. Does that help? I need to do a few calculations!
 

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Discussion Starter #8
That sounds very optimistic to me. For the mass, I think it would make sense to do some simple calculations:
  1. start with the current mass
  2. subtract the mass of the engine, transmission, exhaust system, and fuel tank
  3. add the mass of all of the EV components
    • motor
    • controller
    • transaxle
    • battery, with cables and housings
    • charger
    • other electrical devices (contactors, etc)
What do you get? You are wanting to do this with a mass increase of only 100- 200 kg, but with the very large battery planned I don't think that will be possible.

A major variable is the battery. You need it to be large enough to have the energy capacity required to reach the range (or endurance, in racing terms) target. Even if you needed minimal range, it needs to be large enough to deliver the power required for your performance target.

The target weight of the Tesla Powered Cobra Race Car in this forum was 1800 pounds (816 kg) with a 30 kWh Kia Soul EV battery; I didn't search the whole thread for the final weight with the original battery pack, or the later upgrade to a 40 kWh Nissan Leaf battery. This vehicle is very similar to this project, in size, construction, and intended use - even using a Tesla drive unit - but is carrying much less battery than 12 Tesla Model S/X modules.
Hi Brian, thank you for your replies. The arrangement I've currently got in mind is locating 12 x Tesla Battery Modules directly behind the driver, with the DCDC, BMS and Junction Box mounted directly above this sizeable block. The Tesla SDU (Rear) would then be mounted behind the batteries in exactly the same way as it is in a Tesla Model S, driving the rear wheels via a Quaife LSD. Finally, the charge would sit above the SDU. This is the best arrangement I've managed to establish diagrammatically so far! As you say, however, the major issue is the huge mass of batteries. This is predominantly where I feel there's potential for improvement as I feel 12 x Tesla Battery Modules is potentially overkill. Yet, I guess I need this quantity if batteries to produce the power and range required!

I should mention that I'd envisaged fitting 255/40 R18s on the rear and 205/40 17s on the front...

The overall layout would be very similar to that of an F1 car, I suppose.
 

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Discussion Starter #9
Actually, thinking about it, 200-250bhp would probably suffice in a car of this size and weight. The issue I'm having is fitting all the components within the chassis. Ideally whatever EV powertrain I end up using wouldn't necessarily be salvaged from scrapped vehicles. Rather bought off-the-shelf...
 

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Ideally whatever EV powertrain I end up using wouldn't necessarily be salvaged from scrapped vehicles. Rather bought off-the-shelf...
That's not really a thing.

An EV powertrain doesn't ever really break, so, there's not really a market for that kind of thing.

There's hardly any market for DIY conversions, certainly not enough to justify a factor run of any components.

The cheapest place and best place to get an EV drivetrain is from an existing EV.
 

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Hi

Have you looked at my device?

https://www.diyelectriccar.com/forums/showthread.php/duncans-dubious-device-44370p15.html?highlight=duncan

It's the old Caterham/Mallock type layout rather than your mid engined approach

I'm using a forklift motor and a Subaru LSD

If I was starting again now I would use a power unit from an EV - something like a Leaf with a new "brain board" - should be able to get 300 hp easily

I'm using most of a Chevy Volt battery - it's in handy modules so it can be re-configured

For motorsport we normally overload stuff - the Volt uses a maximum of 100 kW - I'm maxing out at 400 kW - but only for a couple of seconds

You can buy bespoke power units - but expect to pay an arm both legs and at least one nut

My car cost less than 4000 pounds all up

Expect to pay in excess of 10,000 for one of the "off the self" motors at a LOWER power output

Best bet get hold of a lightly crashed EV and start there - a Leaf or one of those small BMW I3

Are speeds really getting up to the 150 mph levels in hill climbs and sprints? - here the organisers keep the speeds lower by shortening the straights - this enables them to have lower requirements for safety equipment and driver licencing

I used to use a mini with a Lancia twin cam (170 hp) in sprints in the UK in the 80's - the highest speed I achieved was 130 mph on the back straight at Goodwood
 

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Discussion Starter #13
Hi

Have you looked at my device?

https://www.diyelectriccar.com/forums/showthread.php/duncans-dubious-device-44370p15.html?highlight=duncan

It's the old Caterham/Mallock type layout rather than your mid engined approach

I'm using a forklift motor and a Subaru LSD

If I was starting again now I would use a power unit from an EV - something like a Leaf with a new "brain board" - should be able to get 300 hp easily

I'm using most of a Chevy Volt battery - it's in handy modules so it can be re-configured

For motorsport we normally overload stuff - the Volt uses a maximum of 100 kW - I'm maxing out at 400 kW - but only for a couple of seconds

You can buy bespoke power units - but expect to pay an arm both legs and at least one nut

My car cost less than 4000 pounds all up

Expect to pay in excess of 10,000 for one of the "off the self" motors at a LOWER power output

Best bet get hold of a lightly crashed EV and start there - a Leaf or one of those small BMW I3

Are speeds really getting up to the 150 mph levels in hill climbs and sprints? - here the organisers keep the speeds lower by shortening the straights - this enables them to have lower requirements for safety equipment and driver licencing

I used to use a mini with a Lancia twin cam (170 hp) in sprints in the UK in the 80's - the highest speed I achieved was 130 mph on the back straight at Goodwood
That’s very cool! Very similar to what I’m trying to achieve other than the layout, as you say.

I guess a lot of my specifications above are focussed on future-proofing the car, if you will. I would ideally like to make this vehicle roadworthy eventually, even though I know this is extremely difficult. As it is clearly a sports car, I’m keen to give it more credibility by affording a higher top speed. It’s the holy grail isn’t it, even though we rarely reach those speeds on track.

I think I need to revise my specifications, starting lower and extracting more power/speed as the vehicle potentially develops over the years.
 

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Discussion Starter #14
Keeping things simple, then, what setup could you envisage that would provide a little less power than the Tesla configuration I originally posted for less cash and smaller mass? Those Chevy Volt cells look like a good option. Is there an alternative to the Tesla SDU? I’d rather not bolt a motor onto a transmission or transaxle. I like the compactness of this unit and think that perhaps it’s my best bet right now. Correct?
 

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Hi
How much is your Tesla unit going to cost?

For cost effectiveness I would try and get a complete car

The Tesla unit is better in it's actual designed home - under the car

The Leaf unit is more like a FWD IC unit - which makes it relatively easy to fit into a mid engined layout
The BMW unit looks like it could be easy as well

I started some 11 years ago - my car has been on the road for the last 6 years - the options have changed since then!

The mechanical work of building your chassis and sorting the suspension are all as an IC car

The actual mechanical parts of the power unit are also fairly simple

Then you need to mount the batteries
In my car everything is on the floor - I have relatively low rate springs and no anti-roll bars and it does not roll at all

All of that is simple

Then you get to the electronics! - which is well beyond me! - having a complete car means that you can try and con the electronics that it is still in the Leaf or whatever

In your shoes I would be looking at what I can find as a crashed EV
Preferably one that is crashed but still drivable

Decades ago I put a Lancia unit in my mini - start off with a rusty Lancia - left the whole thing in my garden until I had it all working in the mini

See what you can find
Drive some options - we had a BMW I3 at our last 1/8th mile drags
They put it in with "European Sports cars" - in this instance an SLK 230 - the merc won - but by 1/10th of a second

Drive a Leaf

Dunno what else is available these days

Remember the power unit in these cars is expected to last for 300,000 miles with almost no warranty failure

You CAN turn the wick up a LOT and still get respectable "motorsport" reliability
 

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The two big fit issues currently appear to be:
  • the unreasonably large battery, which is being reconsidered
  • the unknown structure and suspension in the rear, which affect what drive units will fit well
Can you name the car design, or provide a photo of the engine/transaxle/suspension area?

Ideally whatever EV powertrain I end up using wouldn't necessarily be salvaged from scrapped vehicles. Rather bought off-the-shelf...
That's not really a thing.

An EV powertrain doesn't ever really break, so, there's not really a market for that kind of thing.

There's hardly any market for DIY conversions, certainly not enough to justify a factor run of any components.

The cheapest place and best place to get an EV drivetrain is from an existing EV.
I generally agree with Matt's assessment, although Tesla proved for years that they can screw up simple gearboxes, so lots of them did fail. There are suitable components manufactured, but they are generally not available to end customers, only to manufacturers who will commit to some substantial quantity; if you find one, it will be very expensive. One problem is that there are so many configuration options that they are not built until ordered in a specific configuration, and that's not practical for small quantities.

One option is to use the drive unit of a production EV, but buy it new. That's expensive, and unlikely to be even possible with a Tesla, but some of us have noticed that a lot of GM parts (including the entire battery pack of the Bolt) are available like any other replacement part, through dealers. I just don't see the value in buying - for instance - a complete new Bolt drive unit when the same thing from a wrecked Bolt will be perfectly reliable.

The advantage of something built for custom or conversion vehicles would be that it would presumably be sold with technical documentation and support; the challenge with motors and associated controllers from production EVs (with or without the stock transaxle) is that they can't be reprogrammed and will only operate by getting the computer network messages which would be expected in the production vehicle.
 

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The Tesla SDU (Rear) would then be mounted behind the batteries in exactly the same way as it is in a Tesla Model S, driving the rear wheels via a Quaife LSD.
That really is the only way to use any of these complete drive units (with transaxle) - they typically can't be rotated to another orientation. That means a Tesla Model S/X motor will be behind the axle line, most others will be ahead of it, and the Chevrolet Spark EV and Bolt motors will be on the axle line.

The fact that someone else has already worked out the installation of a Quaife in the Tesla Model S/X drive units is valuable, since the car presumably wouldn't retain the brake-based traction control functionality of the production EV, and none of these EVs have a limited-slip differential from the factory. I'm sure a Quaife or similar could be installed in other drive units, but work would be required in disassembly, examination of dimensions and bearings, and searching of available parts... and it's not guaranteed that anything will fit.

Is there an alternative to the Tesla SDU? I’d rather not bolt a motor onto a transmission or transaxle. I like the compactness of this unit and think that perhaps it’s my best bet right now. Correct?
Any of the drive units from other EVs (the Leaf is most commonly used in or considered for conversions) have the same advantages as the Tesla units in compactness and inclusion of a suitable transaxle (reduction gearing and differential). There is the motor placement difference that I mentioned above, and of course the aftermarket support for ways to control them varies.
 

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Discussion Starter #18
Hi
How much is your Tesla unit going to cost?

For cost effectiveness I would try and get a complete car

The Tesla unit is better in it's actual designed home - under the car

The Leaf unit is more like a FWD IC unit - which makes it relatively easy to fit into a mid engined layout
The BMW unit looks like it could be easy as well

I started some 11 years ago - my car has been on the road for the last 6 years - the options have changed since then!

The mechanical work of building your chassis and sorting the suspension are all as an IC car

The actual mechanical parts of the power unit are also fairly simple

Then you need to mount the batteries
In my car everything is on the floor - I have relatively low rate springs and no anti-roll bars and it does not roll at all

All of that is simple

Then you get to the electronics! - which is well beyond me! - having a complete car means that you can try and con the electronics that it is still in the Leaf or whatever

In your shoes I would be looking at what I can find as a crashed EV
Preferably one that is crashed but still drivable

Decades ago I put a Lancia unit in my mini - start off with a rusty Lancia - left the whole thing in my garden until I had it all working in the mini

See what you can find
Drive some options - we had a BMW I3 at our last 1/8th mile drags
They put it in with "European Sports cars" - in this instance an SLK 230 - the merc won - but by 1/10th of a second

Drive a Leaf

Dunno what else is available these days

Remember the power unit in these cars is expected to last for 300,000 miles with almost no warranty failure

You CAN turn the wick up a LOT and still get respectable "motorsport" reliability
Thank you for your help thus far. It's much appreciated!

My quote for the entire conversion kit was £33,500... That includes absolutely everything I'd need for the powertrain, apparently.

Unfortunately there's absolutely no chance of getting the battery modules under the car as the driver practically sits directly on the chassis floor and I don't want to increase the overall height of the vehicle. I'm actually quite happy with locating the battery box directly behind the driver as this means I can avoid issues with firewalls at motorsport events. The driver can be protected from potential battery fires more effectively with the configuration I have in mind. The battery box would actually form an integral part of the chassis itself, being mounted as low as possible with two banks of 6 modules side-by-side arranged longitudinally. I am happy this would provide a low enough centre of gravity.

I think I will take a look at the options you've suggested above. Namely the Leaf and Volt. Extracting components from lightly crashed examples does sound like a more cost effective option to the quote mentioned above.
 

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Thank you for your help thus far. It's much appreciated!

My quote for the entire conversion kit was £33,500... That includes absolutely everything I'd need for the powertrain, apparently.

Unfortunately there's absolutely no chance of getting the battery modules under the car as the driver practically sits directly on the chassis floor and I don't want to increase the overall height of the vehicle. I'm actually quite happy with locating the battery box directly behind the driver as this means I can avoid issues with firewalls at motorsport events. The driver can be protected from potential battery fires more effectively with the configuration I have in mind. The battery box would actually form an integral part of the chassis itself, being mounted as low as possible with two banks of 6 modules side-by-side arranged longitudinally. I am happy this would provide a low enough centre of gravity.

I think I will take a look at the options you've suggested above. Namely the Leaf and Volt. Extracting components from lightly crashed examples does sound like a more cost effective option to the quote mentioned above.
33,000 is nearly ten times what I spent! - for the whole car! suspension brakes, body, chassis, certification, the electric car bits - the lot

Getting space for the batteries is one of the most difficult things - I am using the "engine bay" for batteries - the gearbox location for the motor and everything else as per usual

With a mid engined installation the driver is further forwards -
The space between the driver and passenger is now free
Or you could move the driver and passenger closer together and give room for the batteries along the "sills"

I do fancy making another car - I'm thinking of a Jaguar C type look alike but with a leaf power unit in the back and running the batteries along the sills as well as in the "engine bay"

The Tesla modules are not well suited to this type of messing about - the Leaf modules would be easy to configure
Chevy Volt ones are bit larger and have water cooling
 

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Placing the battery modules

If we knew the specific car design it would be easier to make helpful suggestions about configuration.

Regardless of the design, there must be a fuel tank... and that's a potential location for one or more battery modules, depending on volume, proportions, and module dimensions. Although front-engine vehicles essentially always have the fuel tank just ahead of the axle or behind it, mid-engine and rear-engine cars routinely have the tank in the front, just ahead of the cowl (base of the windshield). Since an EV conversion tends to increase vehicle mass, and the full fuel tank had significant mass anyway, it's probably a good idea to place some of the battery there. At the very least, a fuel tank location up front would be a good place for the charger.

Some mid-engine cars have a central fuel tank, in a tunnel between the seats (although that's unlikely in a kit). The Chevrolet Volt actually runs half of the battery in that location - the Volt modules are designed to fit in a tunnel like that, and might also be a good fit in the sills, if the sills are very large. The Volt's tunnel is long because it runs through both front and back seat areas; a two-seat mid-engine car wouldn't have this length of tunnel between the seats, but the "tunnel" row of modules could continue right up to between the front wheels (depending on vehicle structure and body design). Of course a car has either a large tunnel (and wide-spread seats) or large sills (and seats jammed against each other), not both.

I wouldn't want battery modules in sills unless they had very good enclosures and protective structure, because I wouldn't want a damaged (and therefore possibly flaming) module jammed into me in a severe collision.

The Tesla Model S/X modules are designed to lay flat under a floor, and so they work well for that. They can also stack in a large box-shaped area, such as a reasonably long or wide engine bay. They are a pain to fit in most other possible areas. I haven't heard of anyone using Tesla Model 3 modules yet; they are longer and narrower, so might be candidates for sill or tunnel locations. Most other modules are rectangular boxes which are closer to cubes, rather than very flat and wide.
 
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