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Suzuki Cappuccino Conversion

40113 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!

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Any chance that Santa is bringing an update soon?
Not in time for Christmas I'm afraid but a Happy New Year to you all!

I have been making progress but not much of it has been visible so it's not a very exciting update. I've been working out the plan for wiring and ordering relays, switches, cables etc over the last few weeks.

I've made a prototype of the bottom battery box layer which seems like it will work. However, I want to concentrate on getting everything wired first so that I can test the whole system on a power supply before I start on the battery pack.

I'm waiting for some more parts to turn up and I've got a few mechanical bits to do but I should be able to start wiring pretty soon.

I'll try to keep you updated and include some photos next time!
You know that we are all so very much looking forward to the progress. So many projects start but never find completion.
I've been slowly working on a box to contain all the electrical components over the last few weeks. This will be mounted on top of the battery enclosure where the passenger seat used to be. This means that I can have the majority of the wiring in one place and should keep things fairly simple. The box will contain two main contactors, the precharge circuit, the BMS, some charger circuitry, a JLD404 Ah meter (and shunt), an emergency stop button, a battery enclosure temperature display and a low voltage alarm/beacon (triggered by the BMS LV output). I've built the box and checked the positioning of all the components so I will be wiring this up over the next couple of weeks. Then I've got a bit of wiring to do in the 'engine' bay in order to be able to test the whole system with a power supply.

I've also mounted a forward reverse switch where the gearstick used to be. This is an illuminated switch which I've made a custom 3D printed housing for.

Hopefully I will have some exciting new developments over the next few weeks!


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If you can have the AT lever in the stick location, that could create great fun to the unsuspecting with your sleeper. AT kei power and then...wheeeeeeeeeeeeeeeeee you're gone!
I've made some good progress over the last week. The majority of the low voltage wiring has been completed and I was able to power everything up today and spin the wheels!:D

It's still only on a 30V power supply as I've got the battery pack to sort out. I was able to turn on via the key and the forward/reverse switch and throttle worked perfectly. The precharge and contactor circuits seemed to work fine too.

The bad news is that I still have an intermittent problem with the inverter gate drivers/IGBTs. I had this before when testing on a bench but I decided to get it all wired in properly before investigating further in case it was a wiring problem with my test setup.

This is the process I went through today:

- I turned the ignition on, and then to the momentary start position after a couple of seconds. The power supply hit the current limit (20A). (no throttle input and neither forward or reverse selected)

- I knew the problem before had been related to the gate drivers/IGBTs so I unplugged the lead between the driver board and the first IGBT. The whole system then turns on fine and forward or reverse can be selected.

- I then plugged this lead back in. Everything turned on but the PSU hit the current limit as soon as I selected either forward or reverse. (no throttle input). If I then flick back to 'neutral' it stays at the current limit but if I turn it off and back on again it will be fine until I then select forward or reverse again.

- Unplugging the other driver-IGBT leads doesn't help at all so it seems related to the first IGBT lead that I unplugged.

- Eventually, after a few minutes of turning it on and off and fiddling with these leads I got it to the point where I could select forward or reverse without it hitting the current limit but upon applying some throttle the PSU would cut in and out and the motor would turn rather jerkily.

- It then started working perfectly, spun the wheel up fairly quickly without hitting the PSU current limit

- After taking some videos and enjoying seeing the wheels spinning for the first time it then stopped working again. This time there was no PSU current limit but the motor would only jerk back and forth however much throttle I applied (as if one phase was not working?).

- It then went back to hitting the current limit every time forward or reverse was selected

My feeling is that it is something to do with the gate driver or connections on the combi board. The intermittent nature makes me think it's not a parameter issue or a something broken in the power electronics. I had a few suggestions back when I was testing it on the bench that I still haven't tried but if anyone has any ideas let me know.

I have some videos of it working that I'll try to upload later.
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Videos should be here:!Am-VyIvBzOs6g80VvC8oEZoAhPBGgw

The bleeping in the first video is the battery low voltage alarm which I had disabled before the second video as it was getting annoying! The JLD404 hasn't been setup properly yet hence the incorrect amp reading.
Videos should be here:!Am-VyIvBzOs6g80VvC8oEZoAhPBGgw

The bleeping in the first video is the battery low voltage alarm which I had disabled before the second video as it was getting annoying! The JLD404 hasn't been setup properly yet hence the incorrect amp reading.
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I've been having issues with the inverter that I've been troubleshooting over the last few weeks with help from the guys on the Open Inverter forum.

Progress with this is slow but I've been working on a few other things in the meantime.

I've machined out all the components for the battery box. It's all made from a rigid PVC foam which I then fold and glue. Photos to come when I've glued all 5 layers.

Once I've fixed the inverter problem, I shouldn't be too far away from testing with the full battery pack in :D
Fascinating thread - I love the Cappuccino and think it's an excellent choice for a base vehicle. Good luck getting it over the line; doesn't look like you're too far away!
Cheers. It’s a great donor vehicle apart from the lack of space for batteries!

I think that I’ve sorted the inverter problem (thanks to the guys on the open inverter forum). I’m currently working my way through the batteries, charging them up individually and making the battery boxes too. Hopefully should have the battery pack ready in around a months time.

Also discovered that I have a vibration issue with the propshaft now that I can spin it up to full speed. I’m going to add a bearing plate to the front face of the motor in order to support that end of the propshaft. I think the problem lies with a bit of play that exists between the splined motor shaft and the gear that I have adapted to fit the propshaft. I’m going to use part of the gearbox housing that came with the motor to support the gear in a bearing.
Hi I have a cappa in AUS and am thinking of going down this track with mine. Is there no chance of mounting any batteries in where the fuel tank was? So keen to see this finished :)
Nice to hear from you. I'm keen to see it finished too! I've got some time off work over the next few days so I'm trying to make some progress. Currently working on BMS and charger wiring.

You could fit some batteries in the fuel tank space but I don't think you could fit a whole pack in, even if you only need a really low range. I've got a ~20kwh pack and could probably fit no more than a quarter of the pack in there. It's a really awkward shape (I'll try to get a photo of the shape of the fuel tank later) so it would also depend on what format your batteries are in. If they are small cells and you're willing to fabricate a crazy shaped box then you could pack quite a lot in but with any kind of larger format batteries you'll struggle to fit anything in. I've attached an image of the fuel tank space without the fuel tank in place (the subframe is not attached in this photo and has been lowered slightly on a jack so you'd actually have less space than this).

I think you could fit a full battery pack in a Cappuccino (without using the passenger space!) by spreading them around the car - some in the boot (trunk), some in the fuel tank space, and some under the bonnet (hood). I decided that I'd rather simplify the conversion and keep all the batteries in one place. It's a long and complicated project as it is!

My motor and inverter are quite large as well so if you had a more modern and sensibly sized motor/inverter package then you'd have lots more room in the engine bay for batteries. I literally have no space in the engine bay at all. Ideally, you'd want a motor that fitted in the transmission tunnel or within the rear subframe.

Do you have any components yet or are you still at the dreaming stage?!

Edit: for some reason it's rotated the photo but you should be able to make it out. The fuel tank sits right up against the top (the only bit that's not rusty!)


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Hey mate yea a bit of dreaming and some serious thought. Mine is completely stripped and slowly fixing the rust on it. Considering the cost of all the parts from Japan its not too bad an idea. Some useful information if you are looking for a different diff is the auto cappa had a 4.556 ratio. Depending on motor size ill probably be mounting onto the gearbox.
I've wondered if a Lexus 450h Rear Drive Unit or similar would fit under there. It's around 53 kW and would get the Cappa going okay, or a Nissan Leaf drive unit.
Well, it's been a while but the Cappuccino finally moved under battery power today. There are still some inverter parameter issues, a propshaft vibration, and a few odd jobs to sort but I should be very close to getting it on the road. I would add some photos and videos but it doesn't seem to be letting me.
Looking forward to those pics of progress Tom! Well done getting her moving too.

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