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Discussion Starter #1
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!


Tom
 

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Hi Tom,

The Cappuccino is a neat choice. I considered one of those as a conversion candidate myself, but there weren't many around at the time.

Those batteries look good as well, based on the specs and the test done on Endless Sphere. Building the pack will obviously be more time-consuming than using something like Leaf modules, but the advantage is you can package them to fit your available space.

I've been looking at BMS options as well and I like the look of the Zeva BMS. You can combine it with a dash display and it's easily integrated with an Elcon charger. The Thunderstruck TSM2500 charger package also looks to be good value.

It's good to know there's someone else in the north east working on a conversion. I'm in Newcastle myself. Good luck with your build!

Malcolm
 

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Discussion Starter #3
Hi Malcolm.

Thanks for the charger/BMS suggestions - I will have a look into those.

The cells I have bought are actually already assembled into packs of 8 cells in parallel so the assembly shouldn't be too bad. I'm planning on pairing these up to get 16 cells in parallel and then connecting around 80 of these in series. This will give me around 300V and 70aH.

Cheers,

Tom
 

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Hello Tom
This sounds like an exciting build. Don you have any pictures of your car and parts please? I follow with interest.
Cheers
 

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Discussion Starter #5
Thanks for your interest.

Progress has been slow over the winter, hence the lack of updates. The rust was worse than I first thought but I'm now about ready to weld in the repair patches. The floor had practically detached itself from the sill along the driver's side of the car.

I've removed quite a lot of the engine ancillaries so once the rust is sorted I'm hoping that I can progress a bit quicker and get the engine and fuel tank out.

Unfortunately, I don't have many photos at the moment. Mainly because they would just be photos of rust! I have attached a couple. Hopefully I'll have some more interesting photos soon.

Tom
 

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That looks like a great setup and powerful with that reduction direct to the rear diff. In such a light donor you could possibly run it without the reduction. Any idea how much torque it produces continuously?
And how much the battery will weigh roughly?
You'll be much better off packaging without the reduction and tucking the motor right into the transmission tunnel.

Apologies if I'm raining on your parade or teaching you to suck eggs etc etc.
 

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Discussion Starter #9
Yeah, I’m going to run it without the reduction gearbox. Just direct drive to the prop shaft. With the 5.25:1 reduction in the rear diff it should still have enough torque.

I don’t know how much torque the motor produces. The stock engine only produces 64lbft and feels quick. I’m expecting double if not triple that from the motor.
 

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And a view of what's to come. Not the biggest space but with that motor in the tunnel it should be ok. I wonder how much space is available in the fuel tank area to locate chargers or other electronisa. You might struggle with the size of the controller housing but no point speculating yet.
 

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Discussion Starter #11
No problem, nice to know that you’re thinking along exactly the same lines that I am.

Unfortunately I don’t think the motor will tuck very far up into the transmission tunnel as it is so narrow. The stock gearbox is very long and thin.

The full battery pack weighs around 150kg (bare with no connections/cables/casing). I think I might struggle to fit the whole pack in as it’s such a small car. Once I have the engine and fuel tank out I will have a better idea. The fuel tank area looks quite big (relatively!) but it is difficult to access as the entire rear subframe must be removed to get to it.

Weight wise I think the car will end up heavier than stock but hopefully not by much. It’s 725kg as standard so I’m hoping to stay under 850kg at a guess.
 

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Well assuming peak power is at 7000 for guestimates sake, nm = 9.5488 x 90kw x 1000 / 7000rpm = 120nm so x 5.25 = 640nm at the wheels and with stock tyre size is alot! Likely more than the tyres will hold so plenty acceleration.
 

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That sounds reasonable.

I was thinking the fuel tank space must be hidden and good for locating larger items, similar to an mx5. It would be good to put the controller up there to give Mac space for battery and keep good weight distribution. And the fuel tank location is a good place to be able to trim/modify the structure to make space for the controller say. It is not too highly stressed as the subframe and chassis structure wrap round there. Well notionally looking at it. I didn't design the car so take my comments with a pinch of salt until you've stripped the car down properly.

I've seen alot of conversions where builders put some battery in the fuel tank area which is ok but it's a compromise with the longer power cables. If you can split the capacity but keep the same voltage in 2 separate packs that would be ideal and it sounds like that might be possible with your setup.

I look forward to any updates you have, don't let me rush you though. Anyway I need to get off my rear and building my conversion.

Cheers
 

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Hi
If you are going direct drive then you won't need a clutch pedal - with only two pedals you don't need as much space in the footwell - and the passenger never needed that much anyway

I would cut out the transmission tunnel and make a lightweight removable tunnel that the motor would live in

Then you have the whole engine bay for your batteries
 

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If you are going direct drive then you won't need a clutch pedal - with only two pedals you don't need as much space in the footwell - and the passenger never needed that much anyway

I would cut out the transmission tunnel and make a lightweight removable tunnel that the motor would live in
I understand the logic of enlarging the tunnel and forcing the occupants' feet outboard... but the tunnel is probably significant to the unibody structure, so I'm not sure some non-structural piece would be a suitable replacement.

Then you have the whole engine bay for your batteries
It certainly would be good to get the motor out of the engine compartment. :)
 

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Hi Brian - valid point
The easiest way would be to make a new tunnel out of something like 20 mm square tubing to take any loads and to have a bolt on lightweight cover so that you can get to the motor when you want

On my car I closed in the bottom completely - helps the strength and you don't need to let the drips escape - but that does mean that you have to get at the motor from inside the car
 

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On my car I closed in the bottom completely - helps the strength and you don't need to let the drips escape - but that does mean that you have to get at the motor from inside the car
In an open-top car and with the access panel, that wouldn't be unreasonable at all. :)
 

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Discussion Starter #18
Thanks for all the input guys. It's getting me motivated to get this rust sorted and get cracking on the conversion!

My current plan is to split the battery pack between the fuel tank area and the engine bay. With the charger and some other electrical gizmos in the boot and the inverter above the motor at the rear of the engine bay.

What are the disadvantages to splitting the battery pack? Power losses in the long cables? It seems that whichever way it is done (split the battery or put the inverter at the back) the same problem is going to be present.

I could split the battery into two equal voltage packs but I seem to remember reading that it is best to put the cells together in parallel to get the amp hours that are needed and then connect these all in one series string.

I would also rather keep the inverter near the motor as it has a nice 1m cable with connectors that I would rather not mess around with. I have thought about trying to put the motor directly onto the rear diff but there is just not enough room.

The discussion on the transmission tunnel is interesting. I hadn't really considered this, mainly because I'm not sure if there are extra legal hoops that have to be jumped through in the UK if you start cutting into structural parts. Also, the footwell is already extremely small. I'm 6'3" and, although I find it very comfortable to drive (once I'm in!), there isn't much room for manouvre. I will have a look next time I'm working on the car.

I'm hoping to get the rust work finished over Easter and from there it shouldn't take too long to get the engine out. I think I'll need to get the cardboard out after that to make some models for test fitting! It's definitely going to be a puzzle.
 

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Wow those are nice blocks. Shame to break them up.

Regarding batteries, I'd recommend splitting in parallel with same amperage and voltage. So you wire both halves in parallel directly to the inverter or preferably through a junction box with separate pack fuses and even contactors. So you could run off 1 pack at a time in an emergency etc, or if one pack fuse blows you can run off the second etc.

I agree also if it is similar challenge that you split the pack and keep the inverter with the motor rather than move the inverter further away.

Regarding UK law, there are new rules I've not checked but the rule has always been any major changes to structure of the vehicle requires an IVA test same as building a vehicle from scratch. What constitutes major changes is subject to the investigator's opinion but you'll need a basic VOSA inspection to verify the conversion to electric so speak to the centre about any mod to the chassis ref mounting the motor in the tunnel and you should know what's achievable and how far to go. An MOT is always required first but that is easier with an EV.

Regarding mounting the motor in the tunnel and space, if you build a frame into the floor pan with strong box/tube section and load the motor from above your structure should be fine if my stronger. I'd tie it to the side rails of the chassis for added torsional stiffness. And mount the motor slightly offset to passenger side to have good driver leg room as a passenger only needs somewhere to rest their feet.

Any pics of the underside of the chassis would help also, perhaps with a tape measure in view for scale and reference and we can brainstorm a robust design for locating the motor. That is the biggest blocker to begin with because of six and shape in the small car.
 
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