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Discussion Starter #1
Hello all...110% new to the forum and EV cars in general. SO much good stuff to read on here!

Ive had a lot of experience building several IC cars, but want to dive in head first with an EV conversion. In general my mechanical skill level is good, my electrical level not so much (insert mechanical vs electrical engineer jokes here). I'm considering two options, keeping the standard gearbox or getting rid of it and mating the motor directly to the transfer case.

Ive selected a Defender 90 as a conversion vehicle for a few reasons, the body on frame construction helps a lot in the ease of installation of motor, battery brackets etc. even though aerodynamic and drivetrain efficiency are laughable. A large part of it is practicality from a cargo/hose down point of view.

That being said the range I'm looking for isn't huge. This will be mainly my wife's car to commute 50 miles round trip every day in mixed stop and go and 70 mph traffic. So ideally 100 mile range (excuse my ignorance if this is wildly unrealistic).

Performance wise anything that is an improvement on the standard 122 hp (91 kW) / 221 lb⋅ft (300 N⋅m) diesel engine would be welcome.

This is where things get sticky. I haven't selected any components yet, but have read several of the Wiki articles. The 4 steps in sizing a battery seem to me to be excellent if working with a lot of known variables. But...since the existing diesel power of the vehicle is already known, and this takes the vehicle to top speed and gives a certain acceleration, can this not be used as a basis and work backwards from there to reach a needed battery power and energy?

Naturally at a steady cruise speed not all of the diesels 91kW are being used, only a fraction of that. So if anything, in my mind choosing a 91kW motor would give increased performance, albeit a battery to go with it would be unnecessarily large for 100 miles of range. Or just plain not fit in the available packaging space of a Defender 90.

In the end is that a good starting point or not even close?
 

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Discussion Starter #3
Right...an important part.Well, as I'm very unfamiliar with the topic and don't know exactly what size motor/battery Ill need I'm a bit in the dark. That being said going from other conversions Ive seen I know I'm not up to spending Tesla motor money, but neither do I want to go with a forklift motor. So for an AC motor and parts Id guess it'd be in the 10-16k US dollar range.

Unfortunately this project will take shape in the UK, so there would be the matter of importing or sourcing here. But I haven't so far seen prices for parts sourced directly in the UK. I know this is just because I haven't looked around enough though...
 

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So for an AC motor and parts Id guess it'd be in the 10-16k US dollar range.
Ok, that helps... I'd probably start by looking at a wrecked Nissan Leaf which should cost you ~2500 GBP then add more Nissan battery modules if you need more range.

Take a look at Mike Schooling's Leaf based Defender conversion if you need inspiration :)

https://twitter.com/Indra_rt/status/976508071718596608

Unfortunately this project will take shape in the UK, so there would be the matter of importing or sourcing here.
Lots activity in the UK, look up projects by Mike Schooling (here), Chris Hazell (here), Tom De Bree (here), and myself. Damien (here) is also just across the water :)

If you want to see any of these cars let me know...
 

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Discussion Starter #5
Hi Kevin

Those are all very helpful...thanks!

I had seen that Defender you sent but havent seen any project details so far. Interesting to know it uses a Leaf motor...it certainly looks like it moves it along quite well!

What other options would there be as far as aftermarket? Im thinking more in the sense of future support, upgrade-ability or even if the first one works out making a second conversion.

Im still very curious though about the correlation between the existing diesel and choosing an electric motor to replace it.
 

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What other options would there be as far as aftermarket? Im thinking more in the sense of future support, upgrade-ability or even if the first one works out making a second conversion.
You could go more old school and use an motor from one of the smaller manufacturers (see here). However, those solutions are much more expensive than the OEM parts we buy from wrecks (Leaf drive units have been changing hands for 600 Euros). That said, If you are serious about series production then talk to Mike Schooling at Indra or Anne Kloppenborg at New Electric about their certified and supported drive trains :cool:
 

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You could also give the guys at Electric Classic Cars a call, I know they've got 2 Defenders they're converting for customers at the moment, maybe you could buy a kit from them.
 

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Discussion Starter #8 (Edited)
Thanks Dave, Kevin...excellent info. I didn't think the Leaf stuff would be as inexpensive. That being said it did give that Defender 100 very good acceleration! I'm now curious about cruising speed/range with that motor and how many batteries it would take to get to the 100 mile range goal.

I'm still curious about the correlation/conversion factor between an IC engine and an electric motor. Even if just for my own information as for the Defender in particular there's already the Leaf powered one which does very well.
 

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I'm now curious about cruising speed/range with that motor and how many batteries it would take to get to the 100 mile range goal.
Given the Leaf curb weight is 3,300lbs, it's pretty aerodynamic, and has an EPA range of 84 miles (24kWh battery), I think you should assume you'll need ~48kWh for a real world 100 miles range, given the weight and aerodynamics of the Defender.

I've attached a Leaf range chart estimator :cool:
 

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I think Kevins about right on the kWh estimate. The electric classic Range Rover that Electric Classic Cars built last year was 80kWh and had a max range of 200 miles, so I would have thought that 48kWh should be good for 100 mile range. The weight, aerodynamics and parasitic load of the drivetrain in a Defender are all against you though. When I picked up my Tesla Model S batteries off ECC a few weeks back the main guy there took me out for a spin in his mental Beetle, which had 48kWh too. He said it would get 200 mile range at a push but it's probably half the weight of a Defender.

Whats the plan? are you going to attached a motor to the gearbox via an adapter plate or direct drive it?
 

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Discussion Starter #11
Given the Leaf curb weight is 3,300lbs, it's pretty aerodynamic, and has an EPA range of 84 miles (24kWh battery), I think you should assume you'll need ~48kWh for a real world 100 miles range, given the weight and aerodynamics of the Defender.

I've attached a Leaf range chart estimator :cool:

Cool...thanks for that!
 

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Discussion Starter #12
I think Kevins about right on the kWh estimate. The electric classic Range Rover that Electric Classic Cars built last year was 80kWh and had a max range of 200 miles, so I would have thought that 48kWh should be good for 100 mile range. The weight, aerodynamics and parasitic load of the drivetrain in a Defender are all against you though. When I picked up my Tesla Model S batteries off ECC a few weeks back the main guy there took me out for a spin in his mental Beetle, which had 48kWh too. He said it would get 200 mile range at a push but it's probably half the weight of a Defender.

Whats the plan? are you going to attached a motor to the gearbox via an adapter plate or direct drive it?
Looking at the Leaf battery pack as an example it looks like this to me...

24kWh = 48 modules
48kWh = 96 modules

Lets round up to 100 modules just for the math...50kWh, each module is 303 x 223 x 55 mm then a battery pack of 100 modules (only modules no other hardware) split into 4 stacks of 25 modules would be a box of 606 x x446 x 1375 mm. Is that math making sense? If so splitting that box into two taking up the space where the fuel tank used to be and on top of the motor at the front looks to be totally doable.

As for the motor attachment plan there's two options, attached to the gearbox or dump the gearbox and attach it to the transfer case. If they would have made 2 wheels drive Defenders with IFS then Id consider direct drive. But doing that on the Defender would make the front axle completely useless. I think the gearbox attachment route would be best as it gives the option of the 5 gears to play with.
 

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I think the gearbox attachment route would be best as it gives the option of the 5 gears to play with.
No electric OEM cars have a shiftable gearbox today, they just don't need it... that said however, you may find it simplifies the conversion and I suspect that's what Mike did with the Leaf based Defender :cool:
 

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some time ago I done some calculations for my friend as he wanted to convert it to electric, we discussed about an option to use leaf motor and connect it to central diff (it have 2 speeds, low and high, as I know) so you get couple possible reductions to wheels and can place motor in gearbox place.
unfortunately my friend went to a different car, so not done defender project...
 

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No electric OEM cars have a shiftable gearbox today, they just don't need it... that said however, you may find it simplifies the conversion...
Well, no mass-production pure battery electric cars have a multi-speed gearbox, since the original Tesla Roadster transaxle failed and is long gone, the Rimac cars are nearly custom exotics, the cars using GKN's two-speed eTwinsterX are all hybrids, and no one is currently using any of the several available two-speed transaxles intended for electric drive in production.

I agree that with a modern motor (not so much for a forklift motor) only one ratio is needed, and that's the current normal practice.

I also agree that
  • you likely need some gear reduction between the motor and the final drive, and the stock transmission may be the cheapest and easiest (although not lightest or most compact) way to get it, and
  • you may not know the best gear ratio in advance, and shifting the stock transmission is an effective way to change ratios.
 

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Discussion Starter #17
some time ago I done some calculations for my friend as he wanted to convert it to electric, we discussed about an option to use leaf motor and connect it to central diff (it have 2 speeds, low and high, as I know) so you get couple possible reductions to wheels and can place motor in gearbox place.
unfortunately my friend went to a different car, so not done defender project...

That's only sort of accurate though. Yes, it does have 2 speeds, but only in 4WD, and the Defender 4WD system can not be used on asphalt as it doesn't have a central differential. In 2WD its only 1 speed. The only reason to connect it directly to the transfer case is to lose the gearbox.
 

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I think attaching the motor directly to the transfer box and placing it where the gearbox is would free up a lot of space in the engine bay for batteries. Although you'd need to do all the calculations on ratios, both transfer box and diff to see what rpm vs road speed gives you. This page I've just Googled might help.

If I remember rightly the ECC guys were going both ways, one Defender was having the motor attached to the gearbox the other was going to be direct drive. I'm not sure why they're trying both routes, maybe to see which works best, more than that you'd need to ask them. My thinking is that if you're planning on going serious off roading or towing you should keep the gearbox, if it's simply going to be on road then direct drive or through the transfer box could be a viable option, as long as all the ratios are in your favour.
 

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Discussion Starter #19
Well, no mass-production pure battery electric cars have a multi-speed gearbox, since the original Tesla Roadster transaxle failed and is long gone, the Rimac cars are nearly custom exotics, the cars using GKN's two-speed eTwinsterX are all hybrids, and no one is currently using any of the several available two-speed transaxles intended for electric drive in production.

I agree that with a modern motor (not so much for a forklift motor) only one ratio is needed, and that's the current normal practice.

I also agree that
  • you likely need some gear reduction between the motor and the final drive, and the stock transmission may be the cheapest and easiest (although not lightest or most compact) way to get it, and
  • you may not know the best gear ratio in advance, and shifting the stock transmission is an effective way to change ratios.

Yes, that's true that no current EVs have a gearbox...this would only be for simplicity sake. That being said though, would there not be a benefit to keep the electric motor in a certain RPM range to extend the battery life? Or is that completely irrelevant for electric motors, and they use the same amount of power regardless at what RPM they're running at?

The other option which I forgot to mention is getting rid of the gearbox, and replacing it with a 2 speed over drive unit which would give 2 speeds.
 

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I think attaching the motor directly to the transfer box and placing it where the gearbox is would free up a lot of space in the engine bay for batteries. Although you'd need to do all the calculations on ratios, both transfer box and diff to see what rpm vs road speed gives you. This page I've just Googled might help.

If I remember rightly the ECC guys were going both ways, one Defender was having the motor attached to the gearbox the other was going to be direct drive. I'm not sure why they're trying both routes, maybe to see which works best, more than that you'd need to ask them. My thinking is that if you're planning on going serious off roading or towing you should keep the gearbox, if it's simply going to be on road then direct drive or through the transfer box could be a viable option, as long as all the ratios are in your favour.
Thanks for that...Ill have a look at the ratio calculator and input a chosen motor in there to see the rpm/speed it would give.

This would be 99% for onroad driving, and getting rid of the gearbox and just connecting it to the transfer case would be the easiest/neatest installation. Direct drive isn't really an option though as it would render the front solid axle useless and way overkill to just do the suspension/steering work. For a direct drive the ideal thing is a 2WD pick up, or an SUV that is sold both in 2WD and 4WD versions like a Toyota 4Runner.
 
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