# Lotus Excel conversion



## Fightingtorque (Nov 30, 2020)

Hi all,
I've been following the subject of DIY EV conversions for a while and am now making a start. Target vehicle is a Lotus Excel that I found for sale with the ICE bits (and some other bits) already missing. I've got some work to do to put the car back together and then I want to create the chassis as a CAD model and see what might fit - for example Nissan Leaf or Lexus GS450H motors, whether to aim for batteries in the engine compartment, boot, rear seat space etc.

Main interest is in "the project". I've no experience in EVs but quite a lot of experience in rebuilding and modifying classic cars in general. I have built a full engine swap car over recent years.

I'm hoping for performance that approaches that of the original car (160bhp), I am sure top speed will be lower but I'll be happy with reasonable acceleration up to 80mph and not interested beyone that. I'd like sufficient range for local use - let's say 50-80 miles. I work about 15 miles from home, nearest city is also about 15 miles, I live in Norfolk UK where it is pretty flat which probably helps. I'll still use ICE cars for long trips for as long as I can. So I don't really need fast charging for example, I expect it could all be done from home.

Budget wise, I am hoping I can do most of it over a few years on boy's hobby money and then stump up for the batteries when the end is in sight. I can see it is going to be more expensive than an equivalent ICE project but I'm hoping it will be usable as a daily driver once everything is ironed out.

Looking forward to interaction with the members of the forum!

Not expecting this to be a quick project.........

Gav


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## Fightingtorque (Nov 30, 2020)

This is an earlier project: 1969 Scimitar GTE with 24V Alfa Romeo V6, Mazda 6 speed transmission, LSD etc. In total its the product of about 5 different vehicles. Goes like hell.


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## Fightingtorque (Nov 30, 2020)

A better picture of the Excel. So far, I've just about got the doors back on....


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## Fightingtorque (Nov 30, 2020)

Thanks for approving the post!
Still at the thinking stage as it is too cold to do much outside and it can't come into the garage until another project is finished.


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## MattsAwesomeStuff (Aug 10, 2017)

Always happy to see another Lotus project


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## Fightingtorque (Nov 30, 2020)

As the weather is getting slightly better, I took a few measurements and started to look at possible layouts. Hyper 9 with a manual transmission and 4 Tesla modules will fit in the front, I can get 2 or 3 Tesla modules in the boot where the fuel tank normally goes.
Having the manual transmission pushes the motor a long way forward and those batteries are high up. Next I will look at whether the transmission can go further back, whether I can fit a transaxle in the back so that the motor can go right back in the tunnel, or whether I can somehow get the motor installed in the back using an FWD transmission.


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## brian_ (Feb 7, 2017)

Fightingtorque said:


> Having the manual transmission pushes the motor a long way forward and those batteries are high up. Next I will look at whether the transmission can go further back, whether I can fit a transaxle in the back so that the motor can go right back in the tunnel, or whether I can somehow get the motor installed in the back using an FWD transmission.


The Excel appears to use a Toyota W58 transmission, although Lotus used a lot of different transmissions in related models. If it does have that one, the bellhousing is removable (it is bolted on, not an integral part of the transmission case). If you're not going to use a clutch, and you can find a way to shorten the input shaft of the transmission and couple to it, you might be able to shift the motor back by using a shorter housing as an adapter and replacement for the bellhousing. The point of this would just be to get the motor far enough back to let the front drop behind that crossmember which appears to be in the way.

To put a motor in the transmission tunnel, if you can get a final drive with a short enough (high enough reduction ratio) ring and pinion gears you could go without any other transmission.

If you're going to use a motor and transaxle in the back, the easiest design would be to use a complete salvaged EV drive unit (motor and transaxle), rather than adapting a HyPer 9 to a bulkier transaxle that doesn't easily fit in the car.


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## Fightingtorque (Nov 30, 2020)

Hi Brian.... I'm in a few different quandries, mainly:

1. Leaf motor vs. Hyper 9
Hyper 9: performance seems ok, can only buy new so a bit expensive, easier to connect to a transmission, lower voltage so typically would work with 5-7 Tesla modules, meaning good performance lower risk of electrocution during build, cannot be fast charged.

Leaf: performance seems ok, would probably source an entire car, probably the cheapest option, existing transmission might be useable but if it can't then it is harder to mate, 360V means for a lightweight car (i.e. 24-30kWh) you really need to use Leaf betteries, which are not as good as Tesla. More chance of electrocution, or rather death by electrocution, during build.

In my opinion the biggest factor here is the different voltage of the two motors which drives choice of battery (important), ability to fast charge or not (less important for me), and likelihood of death by electrocution (would be interested in advice on that).


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## Fightingtorque (Nov 30, 2020)

2. Manual transmission or single speed.
These motor options, whether Leaf or Hyper9, are a bit marginal performance wise. The car was originally a 2.2 litre with 160Bhp, revved to 7000 rpm. It's going to be a lot of work and quite a bit of money to build, I want it to be fun to drive. I think the different ratios afforded by having a manual transmission would enable this, even moreso if it is possible to shift on the move, but quite well even if not.
On the other hand, the extra space taken up by the transmission may compromise the layout, leading to for example high centre of gravity, the extra weight of the transmission is also a negative but that's a secondary factor. As Brian mentioned above, the Excel came with a Toyota transmission, but I got the car with the transmission already missing so I am open on that. My go-to would be MX-5 because I've got an MX-5 transmission in my Scimitar, so I have an adaptor plate on CAD already and they are cheap and strong enough, but they do seem to be pretty long.
If not using a manual transmission then what? Well, the Leaf has a single speed transmission which would work if I can get the motor and trans in the back. There are some single speed transmissions coming on the market for in-line applications, but I'm not sure I've seen a price yet. I'm guessing £2k which is quite expensive compared to a used MX-5 transmission and adpator.


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## Fightingtorque (Nov 30, 2020)

3. Overall layout
This will drive the packaging efficiency, centre of gravity height, weight distribution and polar moment of inertia. Having half the batteries in the front and half in the boot might make for good weight distribution but the polar moment of inertia will be high. Similarly with a rear mounted motor, might not be great.....

1. *The obvious one - front motor, with manual or single speed transmission, rear wheel drive*. 
Probably 4 Tesla modules under the bonnet. I think I could fit 3 in the space where the petrol tank was. I think I can maybe get one under each of the seats, although it will compromise the rear footwell. 
Another possible battery location would be the rear seats and convert it from being a 2+2 to a 2 seater. This location for batteries would be great for weight distribution, the shape isn't convenient for Tesla batteries but could be suitable for others (LG Chem, Leaf). I have another 2+2 car (my Scimitar) and I almost never use the rear seats.

2. *Front motor, rear transaxle*. 
I am interested to see whether a transaxle such as that used in Porsche 924 or 944 would fit in place of the diff. This would solve packaging problems by allowing the front mounted motor to go a long way back into the transmission tunnel, probably meaning that the batteries can start from right down near in line with the bottom of the chassis.

3. *Transverse mounted rear motor*. 
I've got to build a CAD model of the rear part of the chassis to see if this is viable. This could be an ideal one for the Leaf motor and trans or a Hyper9 with an FWD manual trans.

4. *Rear motor, rear transaxle.* 
Following from idea 2 above, I did wonder whether I can put something like a Beetle transmission in the back and rear mounted motor.

Options 2,3,4 all depend on how things go when I get the rear part of the chassis measured up. The issues are overall space without modifying the actual chassis, and also being able to provide the mounting points for the rear suspension links. That part that provides the mountings is a bolt on part on the Excel, so it can be modified but obviously those mounts need to be in the right location and well supported. The transmission could be made a structural member. On the earlier Lotus Eclat and Elite, those suspension mountings were part of the actual chassis. This was one of the attractions to me of the Excel. In the UK, the rules around retaining a cars original registration make it highly preferable to retain an "original, unmodified chassis". 

In general with fibreglass bodied cars in the UK, you can then cut as many chunks out the fibreglass as you like. I'm not quite sure of the situation with these Lotus models, because the early Elites and Eclats suffered from corrosion of the chassis, so Lotus went to some trouble to convince the DVLA that the chassis was a subframe and registration should go with the body. They did this so that their customers could replace the rusty chassis.

Here are some pics - not my own, I haven't taken the body off..... yet.


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## Fightingtorque (Nov 30, 2020)

4. Awesomeness.

Not to be overlooked..... it should look good under the bonnet. Here is my Alfa powered Scimitar (not quite finished at this point but in action already). After spending some years working on something, you need to be able to look at it and be proud of it, and ready to be judged for what you've done.


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## Duncan (Dec 8, 2008)

Stick a Leaf motor and transmission in the back - you can get 300 hp out of those units with an aftermarket controller


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## Fightingtorque (Nov 30, 2020)

Hi Duncan, thanks for that. It was what I was thinking when I first got the car. 

What would you reccommend for batteries to get the required 360V but I probably only want 24-30kWh. Would you use Leaf batteires? I've heard good things about Chevy Bolt but I'm in UK and not seen them for sale here.


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## Duncan (Dec 8, 2008)

Its going to be a case of use whatever you can get your hands on!
Batteries from a production EV are going to be much better than "new" batteries and cheaper
Leaf batteries are about the worst - but they are still pretty good
Can you find a complete crashed Leaf?
What does a Leaf go for in the UK these days? - if you get the whole thing then you have everything that you need 
A quick look at Ebay shows Leafs for about 4000 pounds - as a road legal operating car 
That gives motor, controller, batteries, charger - plus lots of Leaf bits you may be able to sell

Or look at other EVs


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## brian_ (Feb 7, 2017)

Fightingtorque said:


> Hi Brian.... I'm in a few different quandries, mainly:
> 
> 1. Leaf motor vs. Hyper 9
> Hyper 9: performance seems ok, can only buy new so a bit expensive, easier to connect to a transmission, lower voltage so typically would work with 5-7 Tesla modules, meaning good performance lower risk of electrocution during build, cannot be fast charged.
> ...


Mostly valid, but I personally wouldn't worry about the risk of higher voltage. If you accidentally make your body part of a circuit for a source capable of delivering hundreds of amps, I doubt it matters a lot whether it is at 120 V or 360 V, but I could be wrong.

Any production EV is a potential source of battery modules, but if you need 360 V it does mean using an entire pack worth, and Tesla packs are too big while plug-in hybrid packs are too small... that's certainly an issue. In a similar capacity to the Leaf (40 to 60 kWh) there are the various Hyundai/Kia models and the Bolt, for instance. There are also modules not identified as from any specific production EV.

I don't see why using a Leaf motor would mean that you need to use Leaf battery modules, unless you would be planning a "whole system" transplant in which the stock Leaf controls are used and every component of the system needs to be talking on the CAN bus as Nissan intended.


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## brian_ (Feb 7, 2017)

Fightingtorque said:


> What would you reccommend for batteries to get the required 360V but I probably only want 24-30kWh. Would you use Leaf batteires? I've heard good things about Chevy Bolt but I'm in UK and not seen them for sale here.


The problem with using modules from a pack that is much larger than you want, at the same original voltage, is that using a fraction of a pack gives you the same fraction of the voltage. 30 kWh of the 60 kWh Bolt (or Leaf+) pack would only be 180 volts. There's no point in using the 24 kWh or 30 kWh Leaf packs if you can get the 40 kWh Leaf pack, since they're all the same physical size (volume and weight).

24 to 30 kWh at 360 V is an awkward size for using salvaged production battery components, because plug-in hybrids are half that capacity or less (so modules would need to be paralleled) and modern battery-electric vehicles typically have at least 40 kWh. Perhaps practical approaches might include:

use all of a 40 kWh pack (from a recent Leaf, Kia, Hyundai, etc) and accommodate the larger-than-desired battery pack
use most of a 40 kWh pack and settle for somewhat lower voltage
use aftermarket modules: for example, 16 of the 2.2 kWh 6S2P CALB modules from Zero EV would be about 35 kWh and 360 V (and 192 kg and £9120 GBP)


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## MattsAwesomeStuff (Aug 10, 2017)

brian_ said:


> Mostly valid, but I personally wouldn't worry about the risk of higher voltage. If you accidentally make your body part of a circuit for a source capable of delivering hundreds of amps, I doubt it matters a lot whether it is at 120 V or 360 V, but I could be wrong.


It doesn't matter how many amps they can deliver, an AA battery can deliver enough current to kill you 10 times over. All that matters is whether the voltage is high enough to cause a lethal amount of amps to flow.

120V DC isn't especially dangerous. You can touch it, and it might sting a bit in most circumstances (it could be fatal, but you'd almost have to be trying). Even 120V AC will generally, hurt, but not kill you, though it's 10x as dangerous as DC because of capacative coupling.

Above 120V, AC or DC, is going to start to be regularly lethal. 240V ... almost certainly. 360V, yep.

That said, I do agree with your conclusion, I wouldn't let the battery voltage weigh into danger. You don't play around with it, you have a safety plug right near the battery that disconnects it, you don't work on it while it's live, etc. The electricity doesn't reach out at you like a monster in the night.


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## Duncan (Dec 8, 2008)

MattsAwesomeStuff said:


> It doesn't matter how many amps they can deliver, an AA battery can deliver enough current to kill you 10 times over. All that matters is whether the voltage is high enough to cause a lethal amount of amps to flow.
> 
> 120V DC isn't especially dangerous. You can touch it, and it might sting a bit in most circumstances (it could be fatal, but you'd almost have to be trying). Even 120V AC will generally, hurt, but not kill you, though it's 10x as dangerous as DC because of capacative coupling.
> 
> ...


Nope its the other way around AC is a LOT safer than DC - AC will deliver a fluctuating voltage/current - your heart can cope with that
DC delivers a continuous flow and THAT buggers up your hearts control system

ALWAYS treat DC above 48 volts as lethal - 

240v AC as used in most of the world is not very dangerous 
120v DC is DANGEROUS


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## Duncan (Dec 8, 2008)

brian_ said:


> Mostly valid, but I personally wouldn't worry about the risk of higher voltage. If you accidentally make your body part of a circuit for a source capable of delivering hundreds of amps, I doubt it matters a lot whether it is at 120 V or 360 V, but I could be wrong.
> 
> Any production EV is a potential source of battery modules, but if you need 360 V it does mean using an entire pack worth, and Tesla packs are too big while plug-in hybrid packs are too small... that's certainly an issue. In a similar capacity to the Leaf (40 to 60 kWh) there are the various Hyundai/Kia models and the Bolt, for instance. There are also modules not identified as from any specific production EV.
> 
> I don't see why using a Leaf motor would mean that you need to use Leaf battery modules, unless you would be planning a "whole system" transplant in which the stock Leaf controls are used and every component of the system needs to be talking on the CAN bus as Nissan intended.


Using a leaf as a donor car
There are effectively three ways
(1) Use the whole lot and convince the electronics that it still in the Leaf
This should be the cheapest way to get all of the functionality - HOWEVER a number of people have tried that and I'm not aware of anybody actually making it work

(2) Use all of the Leaf bits and your super skills with CanBus to get it all to work nicely
Requires skills I don't have - but YOU may be able to "tool up" and do it

(3) Use the physical bits and the expensive electronics - the power handling stuff - and substitute the "brain boards" for aftermarket parts that you can tell what to do


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## MattsAwesomeStuff (Aug 10, 2017)

Duncan said:


> Nope its the other way around AC is a LOT safer than DC - AC will deliver a fluctuating voltage/current - your heart can cope with that
> DC delivers a continuous flow and THAT buggers up your hearts control system


You won't find many who hold that opinion. Not in that specific context or in that general conclusion.

AC is generally thought of as about 5x as dangerous as DC (I said 10x earlier, that was a bit exaggerated), due to the effects of capacative coupling.









Which Current Is More Dangerous, AC Or DC?


Have you ever had an electric shock? Well, many people think that DC current is more dangerous than AC current as far as an Electric shock is concerned.




www.electronicsforu.com





Also, even if 5x more current wasn't flowing with AC and it was the same amount of current flowing, you're wrong about the effect on the heart. Your heart can handle DC, in fact that's what a defibrillator does, stops your heart so that it can restart itself with a regular rhythm. 60hz AC is about the worst case for your heart.









AC or DC - Which One is More Dangerous And Why ?


Which is More Dangerous - AC or DC? Why AC is More Dangerous than DC? Is DC Voltage really Dangerous than AC Voltage. Which is Harmful, AC Current or DC Current.




www.electricaltechnology.org





"Due to the alternating nature behavior of AC, it causes to heart’s pacemaker neurons into *atrial fibrillation* which is more dangerous than DC, where *cardiac standstill* (due to ventricular fibrillation) occurs in case of electric shock. In this case, there is a better chance for “frozen heart” to get back on the normal track as compared to fibrillating heart caused by AC. In that cases, defibrillating equipment (which supply DC units to halt the fibrillation and bring back the heart to the normal condition) are used as emergency medical service. "



Physics 516 & 616: Intermediate & Advanced Undergrad Labs








IEC 60479-1 - Effects of current on human beings and livestock – Part 1: General aspects | Engineering360


Find the most up-to-date version of IEC 60479-1 at Engineering360.



standards.globalspec.com





“Accidents with direct current are much less frequent than would be expected from the number of DC applications, and fatal electrical accidents occur only under very unfavourable conditions, for example, in mines. This is partly due to the fact that with direct current, the letgo of parts gripped is less difficult and that for shock durations longer than the period of the cardiac cycle, the threshold of ventricular fibrillation is considerably higher than for alternating current.”



> 240v AC as used in most of the world is not very dangerous. 120v DC is DANGEROUS


Yeah, I wouldn't agree. 240v AC is regularly fatal. 120v DC can literally be played with and is somewhat considered the bottom threshold for danger.

Electrical slapstick aside, Medhi is an electrical engineer, and has actually used himself as a human guinea pig to test pain thresholds with both AC and DC. And, even sweaty, bare hands, touching 120VDC he can barely feel a tingle:


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## Fightingtorque (Nov 30, 2020)

Thanks for the info. I'm still thinking about it. I'll know more when I get the whole chassis done in CAD. Had a bit of a setback with one of my ICE cars which will take a little time to fix.


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## EddyM (Nov 16, 2021)

How is the Excel conversion progressing? I've just bought a beaten up 1985 Excel for a conversion project - a busy winter awaits!


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## remy_martian (Feb 4, 2019)

MattsAwesomeStuff said:


> It doesn't matter how many amps they can deliver, an AA battery can deliver enough current to kill you 10 times over. All that matters is whether the voltage is high enough to cause a lethal amount of amps to flow.
> 
> 120V DC isn't especially dangerous. You can touch it, and it might sting a bit in most circumstances (it could be fatal, but you'd almost have to be trying). Even 120V AC will generally, hurt, but not kill you, though it's 10x as dangerous as DC because of capacative coupling.


AC is dangerous because it induces fibrillation in the heart, not because of AC coupling. 0.008A or so through the heart will do it. Skin is high impedance, less so when wet, which is why higher AC is lethal, but it's the current through the heart that kills (ignoring getting cooked by high currents, AC or DC). Correct practice when working on HV is to keep your left hand in your pocket.



> The electricity doesn't reach out at you like a monster in the night.


There are a lot of dead guys, who carried aluminum ladders NEAR a HV power line, who would disagree with you if they could. There's a macabre video on the Intertubes that shows a mentally ill guy dancing/taunting authorities on top of a train - he's instantly barbequed when his proximity to the train caternary line is such that a spark jumps at his grounded azz. High voltage WILL jump to a grounded (or return polarity) without touching it. At our voltages, unlikely, but a number of factors enable it to, so treat HV with the respect that it CAN reach out to you like a monster in the night.


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## schelle63 (Jan 3, 2018)

Both high voltage and high current deserve lots of respect.
There are devices available, which constantly measure the resistance between both plus and minus from the HV-battery and the chassis' ground (should be in the range of M-ohms), and which will instantly open the battery's main contactors if needed. Our Renault Clio électrique from 1996 already had it.

As far as I know, AC will affect you (much) more than DC, but DC makes it impossible to release any cable if you managed to grab it.

Anyway, if everything goes right, we should never know.


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