DIY Electric Car Forums banner

Suzuki Cappuccino Conversion

40116 Views 96 Replies 11 Participants Last post by  tylerwatts
Hi all.

I’ve been lurking on these forums for quite a while but I have finally begun a conversion.

The donor is a 1994 Suzuki Cappuccino. For those who don’t know it’s a tiny Japanese kei sports car weighing around 725kg stock. It comes with a 660cc 3 cylinder twin cam turbo engine as standard in front engine RWD layout. Great fun to drive even with its 64hp power output.

I have begun work on the car to get it ready for the conversion. They all have a problem with rusty floors and although mine is a good example it needs some welding before I can go any further.

I have one of the Enova 90kW AC induction motors which I have been able to get turning on the bench using Damien’s combi control PCB controlling the original Enova power electronics. The plan is to connect the motor directly to the prop-shaft for direct drive (diff ratio is 5.125:1). I believe this should give me pretty good performance considering the motor has around twice the power of the stock ICE.

Recently, I obtained some Boston Power Swing 4400 batteries. They have been used but seem to be in pretty good condition. I have around 20kWh in total but I’m unsure whether I will be able to fit them all in! I will be using the car for my commute which is 19 miles each way. I can charge at work but would like to be able to get there and back comfortably on one charge so I’m aiming for a 50 mile range.

The biggest unknowns at the moment are the charger and BMS options. I need to do some research on this as this is the area I know the least about and seems to be the biggest minefield!

I’ll try to keep you updated with progress and I’m sure I will have plenty of questions!

41 - 60 of 97 Posts
i've got an old jaguar and i can completely understand the frustration of having to weld up rust. it seems whenever i finish some i find more and small jobs turn into big ones. I'm an amateur welder as well so my skills never meets the requirements. like you i wondered if i should find another car and then decided to stick with it but persist with the conversion as is, leaving the remaining rust bits. that way i dont feel like i'm never going to complete it. I'll keep an eye out for a better example and may reshell the conversion in the future. That or wait until i win lotto and pay someone else to fix it for me.
I did a test fit of the motor and inverter at the weekend. Unfortunately I wasn't able to get the motor fully into position as it wouldn't slide underneath on a jack and is too heavy to lift in from above. I'll need to borrow an engine hoist again to do this. It looks like it will fit and will mount quite easily on the subframe though.

The inverter is a really snug fit - I didn't realise how big it was until I put it in the car! A photo is attached. I had forgotten about the water cooling pipe outlets which mean that it sticks further out into the space that I was planning to use for batteries. With the inverter in place I think I'm only going to be able to fit 8 batteries in the front and even that is going to be quite a squeeze. This will bring the number down to 21 (233V nominal, 16.4kWh). I'm not sure that I'm going to be happy with this so I'm considering a few different options.

I could try to reduce the size of the inverter. There is a fair amount of empty space inside but I'm not sure that I will be able to reduce the size enough to gain much/any more space for batteries. It would mean machining a new water cooled base plate so I don't think the slight gain in space would be worth the effort.

Another option I'm considering is removing the passenger seat. I could fit the entire battery pack (28 units, 310V, 21.8kWh) in the passenger space and it would simplify the conversion quite a lot. The main purpose of this car is a fun and cheap car for me to commute in (40 mile round trip) so not having a passsenger seat wouldn't be the end of the world.

The issues with the plan to split the pack between the engine bay, boot, and fuel tank are:

  • smaller than ideal pack size
  • lots of batteries just behind the front bumper and just in front of the rear bumper worries me from a safety point of view
  • weight distribution probably isn't ideal (batteries in front of front axle and behind rear axle)
  • radiator would need to be relocated
  • no room for spare wheel or roof panels in the boot
  • quite a lot of design work needed for three seperate battery boxes
  • complex wiring and long cables between different parts of the pack
  • not much room left for things like vacuum pump, water pump, contactors and charger
Putting the batteries in the passenger space would solve all of this. The only downside is the loneliness! :D

I'm still weighing it up at the moment. I don't really need to make a final decision until I've had the welding done so I will see if there is any other way around it over the next few weeks.


See less See more
Putting the batteries in the passenger space would solve all of this. The only downside is the loneliness! :D
Quite a few racing cars have been built with a side-mounted engine, and it works well, for the same reasons (central mass position, large volume available) and others.

Only you can decide how important passengers are. Do you want to let people experience your car without letting them drive? If you do want to let them drive, do you want to ride along?

Here's an out-of-the-box idea: build it with the battery in the passenger seat area, get the EV system sorted out, then as a follow-up project do a scratch-built structure and body with more room for the battery and transfer all of the components (possibly including the Cappuccino chassis bits) so it can have two seats.
So I test fitted the motor today. Thankfully there were no suprises - it actually fits quite nicely! I should be able to use one of the mounts that came with the motor along with a simple bar to support the back of the motor.

What is the general consensus on rubber motor mounts? It will be easier and simpler for me to just bolt/weld the solid mounts directly to the subframe. I've read a few threads giving pros and cons but personally I don't really see the need for rubber mounts.

The attached photo shows the front motor mount roughly in position.


See less See more
Hi Tom. thanks for the link from the Enova 12v discussion we are having. You certainly have/had your hands full with the rust bug. Invest in a TIG welder, you can control the weld a bit better in my humble opinion for thin sheet.
Looks so much easier with front motor and rear wheel drive, my transverse rear drive set up in the Smart has been a challenge so yours should be done a lot quicker.
You could trim the Enova heatsink quite a lot if necessary. Attached pic of initial cut down plate. It did have one of the attached pipe fittings (I broke off later to use plate as a welding heatsink) the cut section of the cooling channel I was going to make a stub to fit a new connection. Makes the whole heatsink half the size :) Let me know if thats an option for you. Plenty of machining time spare and welder at the ready. Speak soon. Peter P.S. Dont forget the splines on the motor, I used a cheap clutch plate from Ebay which fit nicely. Alternatively if you strip the gearbox the primary gear will fit (obviously) but you will have to machine it down and its been hardened so that may prove a grinding job if not careful. I will ask my buddy to see if he can machine it on the lathe.


See less See more
Hi Tom. Sorry for the confusion, I am having two conversations at once and got mixed up thinking we were talking about the Enova 12v converter. Engage brain this time :) Peter
No problem Peter :)

I've arranged for a guy to do the welding for me as I didn't want to get bogged down with all the rust. It should be getting fixed at some point in the next couple of weeks. I do have access to a TIG welder at work - I've had a few attempts using it but I find it very difficult to have a steady enough hand. The guys on Youtube make it look so easy!

I think I'm going to stick with the inverter at its original size (at least for the time being) but thanks for your offer. I do have acces to a machine shop at work but I'm trying to keep things as simple as possible so that I can get on the road quicker.

The plan for connecting the motor to the propshaft is to use the primary gear from the gearbox as you suggest. I have already stripped the gearbox down but I haven't tried machining the gear yet. I'm hoping to give it a go on the lathe at work this week.

I've ordered a second hand propshaft (from a Bentley!) that should be turning up on Tuesday. The original propshaft is obviously too short and it seemed easier to find a new propshaft the correct legth rather than extending the old one. The first one I found on eBay that was roughly the right length was from a Bentley Turbo R! It was cheap so I thought I may as well give it a go :D. The plan is to machine an adapter plate for each end so that I can bolt the prop flanges to the diff at one end and to the primary gear at the other.

I put the motor in position today ready for test fitting the propshaft when it arrives. Once I'm happy that the propshaft, adaptor plates, and motor all fit together nicely I will get the motor mounted permanently.



See less See more
Hi Tom. A step closer with motor in temporary position, all fits nicely. Dont forget your cooling pipes, I had to buy some elbows to allow pipes to fit on my install, elbows in stainless of course :) You struggled a bit with TIG, so did I at first, especially as mine has HF start which is a wake up call if I forget to attach the earth/ground lead. Not managed to zap myself yet but give it time. Let me know how you get on with turning the gear, my colleague is a toolmaker by trade and has all the equipment and turning tips if you are struggling, fingers crossed. All the best. Peter
I've made some progress over the last few weeks, some photos are attached. The adaptor plates for the propshaft have been made and the motor mount has been tacked in place. The Bentley propshaft is the perfect length and fits really nicely in the transmission tunnel, if a little snug! It's nearly twice the diameter of the original one! The only snag that I have hit with the drivetrain is that the gear that I was planning to use to go from the motor splines to the propshaft flange is proving impossible to drill. Everything else is ready to be bolted together.

The options I have for the gear are

-try to anneal the gear and then reharden after drilling. Someone also suggested trying to 'soften' the spots where I need to drill using a welder or similar. Might be worth a try before I give up on it.
- find some special tooling that will drill the hardened steel
- get a new part machined from scratch that has the correct spline
- find another off the shelf (wheel hub, clutch plate etc) part with the same spline
- check the Enova gearbox output flange to see if that has the same splines 9for some reason I haven't done this yet!)

I also bought a electronic throttle pedal from a Rover 75 to give me the 0-5V input I need for the inverter. It was an early electronic throttle that had a seperate pot connected to the pedal with a linkage. I'm planning to use the Cappuccino's original pedal and mount the pot from the Rover pedal in the engine bay and actuate it with the original cable from the Cappuccino.

The car should be going off to the welders this week to have the floor and sills sorted. Once it is back hopefully I will be able to get the motor connected to the wheels :D.

On another note, I have been looking into the BMS options for the battery pack. I'm planning (at least initially) to use the passenger seat space for the battery pack. This means that I can fit the full pack in fairly easily (28 blocks of 3s16p giving a total pack of 84s16p 310V 21.8 kWh nominal). I don't really want to spend a fortune on an all singing all dancing BMS and I'm not sure that I need it. I should have more than enough capacity for my needs so my plan is to limit the charge voltage to something like 4.15V per cell. I will then monitor individual cell voltages with a HV (4.2V) and LV (2.75V?) cutoff. I'm looking at the Zeva 8 cell battery monitors to do this ( In addition to this I will have an Ah meter such as the JLD404 to use as a 'fuel' gauge. Any thoughts on this approach? I know there are a lot of different opinions on this topic! As far as I can tell as long as I balance the cells before they are assembled and stop any cell from going over 4.2V whilst charging and under 2.75V whilst discharging then I should be good. I may loose a bit of range as cells become slightly unbalanced but I should have enough extra capacity to cope.


See less See more
Looking very good. You'll need a carbide cutter to drill that sprocket and a very large pillar drill or ideally a mill. Should be a simple job for a tool maker however so try locally for someone to machine it for you. Not worth annealing it then hardening and too thick to anneal locally... Can't risk softening the splines!
Hi Tom. Would you like me to try machining the primary gear ? If so send me a drawing of what the final splined unit is to be and I will let you know the progress. If all goes well we can swap gears so I have an original :) Thanks for the link to the BMS too, I am investigating and my credit card is twitching ! Peter
Thanks for the offer Peter. I'm going away for a couple of weeks tomorrow so I will have a look at the primary gear again when I return and let you know what I decide.

In other news, the car has been to the welders this week and has returned today with no more holes in the floor :D.

I finally managed to machine the hardened gear last week. I did it by machining through the top few mm with a carbide end mill before drilling the rest of the way with a cobalt drill. It was an absolute nightmare but I got through it eventually! :D
I've got a bit more painting to do on the parts that have been welded but I'm not far off being able to mount the motor. I'm having a few problems with the inverter though which I need to sort with the motor on the bench before I go ahead and put it in the car for good.
Hi Tom. I am also working on my inverter parameters at present. What I expect to happen doesnt seem to be however. One thing I will say is be careful with Boost, dont set that too high or the instant torque will be detrimental to whatever else the motor is driving. I have asked Damien Maguire if he will give me some insight into fslipmin, I asked that because the Enova motor states two frequencies on the name plate... 121Hz & 305Hz. If we use Johannes equation for the 121Hz we get a negative value for fslipmin... that cant be right, but I need a definitive answer to be sure. The equation works for the 305Hz and gives a positive value but I am not sure if thats the one we should use ? I do have the motor rotating with gearbox connected and one wheel jacked up but its definitely not right yet. Maybe we could collaborate on settings and see if we can get a good result. Peter
P.S. For those who know Damien in one way or another... he is in hospital at the moment, lets wish him luck and a speedy recovery.
See less See more
Hi Peter.
As far as I can tell the parameters that I am using work well (at least with a 30V PSU, I suspect they will need to change for 300V). I don't think the intermittent problem that I'm having is parameter related as it spins really nicely when it occassionaly decides to work!
My parameters are based on what Damien sent over to me but I did tweak them a bit. I haven't got the kit all powered up at the moment so I can't download the parameters I'm currently using. I've attached the last set of parameters that I saved which I'm pretty sure are very close to what I'm using now. I've also attached the parameters that Damien sent me.
Sad to hear that Damien is in hospital. Let's hope he has a speedy recovery.
If you haven't already, make sure that you put the latest firmware on the board from the Huebner website as there is a fairly recent fix to ensure the PWM pins are actively pulled down at start up.
Forgot to attach the files!


Hi Tom. Thanks for the parameter lists. Somehow I think my micro or pcb may have a bug ! No matter what I do with the parameters the motor jumps around like mad, some settings its not too bad others it tries to rip itself apart. Also it doesnt save the last set of parameters properly. Next power up it has saved some of them and reverted to ones from a session before ! I am using a wifi link which could be the issue as its a bit hit and miss somtimes and I have to keep refreshing the link as well as the page. Are you talking to your system direct via USB ? If its anything other than wifif please would you tell me how you are doing parameter changes please, thanks. Frustration has gripped me big time today !! All the best. Peter
P.S. Its thrown so many ERROR signals which shut down the main Kilovac style contactor each time that the contactor is now knackered, wave goodbye to £130.
I'm using a USB cable, it's just a printer cable. I've been using this web interface to change/view parameters - I struggled with the standard Huebner web interface. If you download the one in the link and double-click Hueber Inverter.bat (Windows Batch file) with the inverter plugged into a USB port it will automatically connect and open your web browser.

Are you using a power supply or batteries? I've been using a 30V 20A power supply without a contactor. Also, are you using a 0-5V signal for the throttle (automatic mode) or setting the frequency in the software (manual mode)? I've had trouble getting it to work properly in manual mode. It runs better in automatic mode.

I'm also a bit frustrated at the moment with my inverter problem. Not sure if you've seen my posts in the Huebner inverter thread but I have an intermittent issue where the inverter shorts as soon as I put it in forward or reverse. I believe both the transistors in one of the IGBTs are being turned on at the same time but I'm a bit stumped as to how to troubleshoot or fix this. The electronics side of the conversion is what I know least about! It's frustrating because I've almost finished all the restoration work on the car and I have all the parts to mount the motor and connect it to the wheels but I want to get the inverter problem solved before I do that (it's awkward to test the inverter in the garage where the car is located). It's also worrying because if this problem occurs when the battery is connected it will immediately destroy the IGBT.

Seems very odd that the errors would have killed the contactor. They are rated to many thousands of cycles aren't they?
See less See more
Just noticed that I've had a helpful reply in the Huebner inverter thread that somehow I'd missed. :eek:
41 - 60 of 97 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.