Suzuki Cappuccino Conversion

40114 Views 96 Replies 11 Participants Last post by tylerwatts, May 14, 2020

tom3141

Discussion Starter · Nov 25, 2017

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

21 - 40 of 97 Posts

tom3141

Discussion Starter · #21 · Mar 21, 2018

I'm hoping to keep them in the original blocks. The busbars can be swapped around within it to change the cell configuration to whatever I need.

I'm not convinced splitting into two equal packs is worth it. Other than the extra redundancy in case of failure, what are the advantages? It seems to me that it would introduce issues with the two packs charging and discharging unevenly. I was planning to connect 16 cells togther in parallel and then 80 of these batteries together in series. If I do what you are suggesting I will need to monitor twice as many cell voltages. I would have to connect 8 cells together in parallel and then 80 of these batteries in series for each pack. I'm open to doing this if it's the best way but I can't see what the advantage is at the moment.

tom3141

Discussion Starter · #22 · Mar 24, 2018

6

Made some progress today.

I'm now ready to weld the floor repair patches in. Hopefully this will be done next weekend if everything goes well. The engine is also now ready to remove. Everything is disconnected apart from the mounts. I may need to remove some more of the exhaust downpipe but I will wait and see if I can lift it out as it is first.

I also got some photos of the transmission tunnel. They are not the best as the car is on axle stands so I was a bit close to get a decent photo.

The main body of the motor is around 280mm diameter by 330mm long. It is around the same diameter as the gearbox bell housing at its largest. Without any modifciation to the structure I should be able to tuck the motor in so that the front face is around 5-6 inches further back than the engine/gearbox interface.

One nice feature of the transmission tunnel is that it is pretty tall. Originally the exhaust ran down the transmission tunnel underneath the propshaft and was completley hidden as it was above the floor line of the car. It will be tight but I think that I may be able to squeeze some of the battery blocks in underneath the propshaft. If they fit in the width and height then I guess I could probably fit 5 or 6 along the length of the tunnel.

When I'm looking at battery packaging how much thought needs to go into cooling/heating? I believe most OEM EVs have the ability to cool their batteries. Is this generally done amongst DIYers as well? I'm just thinking about whether I need insulation and space for cooling around the batteries. I'm not planning to use the car in sub zero temperatures (celsius) as my commute is quite rural and I'm going to keep my 4x4 for icy/snowy days. The Cappuccino was also pretty tailhappy with the stock engine so I think it would be terryfying in slippery conditions with twice the power! Summer temperatures very occasionally reach 25C but are generally high teens. My current plan is not to worry about heating or cooling but obviously just to make sure they are protected from water and dirt.

See less See more

brian_

· #23 · Mar 24, 2018

tom3141 said:
The main body of the motor is around 280mm diameter by 330mm long. It is around the same diameter as the gearbox bell housing at its largest. Without any modifciation to the structure I should be able to tuck the motor in so that the front face is around 5-6 inches further back than the engine/gearbox interface.

If I understand this correctly, the output face of the motor, which is the motor's "front" face but is at the end of the motor toward the rear of the car, will be at about the current rear of the transmission bellhousing. That puts about 127 to 152 mm of the 330 mm length of the motor behind the original engine/gearbox interface, and the rest ahead of it. That sounds reasonable.

It would be really nice to put the motor entirely in the transmission tunnel, but without tunnel modification (or a custom car build) this rarely turns out to be viable.

That is one impressively short engine. I wish I could find something that short to swap into my Spitfire, but I don't think I would be happy with a Kei-class engine for that car. Thus, the consideration of other options, including EV conversion.

brian_

· #24 · Mar 24, 2018

tom3141 said:
When I'm looking at battery packaging how much thought needs to go into cooling/heating? I believe most OEM EVs have the ability to cool their batteries. Is this generally done amongst DIYers as well? I'm just thinking about whether I need insulation and space for cooling around the batteries. I'm not planning to use the car in sub zero temperatures (celsius)...
My current plan is not to worry about heating or cooling but obviously just to make sure they are protected from water and dirt.

If you really don't want to worry about cooling the battery, use one which is designed for use without active cooling in the original vehicle - the common example would be the Nissan Leaf. Heat for a Leaf battery is electric, and optional.

I think batteries which are designed with integrated liquid thermal management - such as Chev Volt and Tesla - are usually hooked up to a radiator even in DIY installation, but the sophistication of the installations varies.

There's a forum thread on Working with Tesla Packs which started in November 2016 and is still active at 215 posts (and counting), with many side-tracks. The subjects of thermal management and housing are not trivial... happy reading!

tom3141

Discussion Starter · #25 · Mar 24, 2018

Yes, you've understood correctly about the motor position. I think I will be happy with that, especially if I can get some of the batteries in the tunnel.

It's a lovely little engine but would need to be put in a car with a similar diff ratio (5.25:1) otherwise it would be really sluggish. Feels genuinely quick in a car this light but a lot of that is due to the ridiculous gearing. You sit at something like 4500rpm at 70mph in 5th. Redline is at 8500rpm!

The battery I have is made up of Boston Power Swing 4400 cells. They did come from a prototype EV but I'm not sure whether they had any heating or cooling. Just checked the data sheet for them (http://liionbms.com/pdf/bostonpower/swing4400.pdf) and the discharge operating temperature is -40C to +70C, charge is -10C to +60C. From the temperature performance graph it looks as though ideally they want to be kept between 30C and 60C. What I don't know is how much heat they will generate themselves under charging/discharging.

Duncan

· #26 · Mar 24, 2018

Hi Tom
Re-battery heat
Probably very little!
You are most unlikely to want to cool your battery - for max performance you probably want to heat it

I'm using most of a Volt pack - which is water cooled/heated - I'm actually using it as the heat sink for my controller
I circulate water from the controller to the battery - keeps the controller nice and cool - provides a tiny amount of heating for the battery

tylerwatts

· #27 · Mar 25, 2018

Tom
I agree with the guys. Given your chemistry all I'd worry about is heating for winter and I'd suggest having air cooling like fans for hot weather. But save that for a future possibility. Ie design your battery boxes so you have space for airflow and fitting a fan but have some insulation in the walls. I'd suggest using angle iron or small 18mm square tube to frame the box and aluminium skin outside. And possibly thin rubber mat to insulate the bricks from vibration. And possibly clamp the bricks top to bottom in the box to keep them together and stable.

tom3141

Discussion Starter · #28 · Mar 30, 2018

I've managed to get hold of a Brusa charger. It arrived yesterday so I now have nearly all the parts I need. The only big thing left is to decide on the BMS options. I'm still thinking of going down the route of a simple overvoltage and undervoltage cut off (no balancing). I'm looking at something like the CellLogs or Zeva 8-cell battery monitor module.

I also noticed something on the motor spec plate yesterday. It has the base frequency listed as 121Hz (3630 rpm). From my research online it appears that this is the frequency at which peak power is available. So, correct me if I'm wrong, I have a peak torque at the motor of (9.5488*90000W)/3630rpm = 237Nm. This gives a wheel torque of 237Nm*5.125 = 1214 Nm. I think I'm right in saying that this is constant between 0 and 3630rpm. 3630rpm equates to around 45mph with the 5.125 diff ratio.

The original engine makes a peak torque of 85Nm at the engine (at 4000rpm), which is 1515Nm at the wheels in 1st gear (3.478 gear ratio x 5.125 diff ratio) or 880Nm at the wheels in 2nd gear (2.021 gear ratio x 5.125 diff ratio).

Looks like I will have plenty of grunt

. I'm hoping for a 0-62mph time of around 6 seconds which seems reasonable.

I've borrowed an engine hoist for the weekend so I'm hoping to get the engine out in the next few days. I'll keep you posted.

See less See more

tylerwatts

· #29 · Mar 30, 2018

You'll have loads of torque for sure!

tom3141

Discussion Starter · #30 · Mar 31, 2018

3

The Cappuccino has been de-ICEd! Got the engine and gearbox out this morning. That leaves the fuel tank as the only part left that needs removing.

I also began the process of welding the sills. Not the most fun job but it's got to be done!

Photos of the empty engine bay are attached. I'm going to make some mock-ups of the motor and batteries so that I can play around with the layout without having to lug the motor around. I'd love to create a Solidworks model of the engine bay to make this easier but without a 3D scanner it would probably take far more time than it's worth and not be very accurate. I think I'll have to resort to Cardboard Aided Design!

See less See more

brian_

· #31 · Apr 1, 2018

tom3141 said:
Attached are some photos of the batteries. Each of these contains 48 cells.

So that a 4x12 array of the Swing cells, each of which is probably a pair of 18650 cells wrapped together and connected in parallel, so essentially an 8x12 array of 18650's... that means something greater than

65 mm tall
8 x 18 mm = 144 mm wide
12 x 18 mm = 216 mm wide
and 48 x 90 g = 4.3 kg
occupying about 2 litres

... per module

Capacity is 4400 mAh per Swing unit, so 781 Wh per module (nominal).

tom3141 said:
I was planning to connect 16 cells togther in parallel and then 80 of these batteries together in series.

So 80s16p Swing units, or 80s32p 18650 cells, for 296 volts (nominal). That's 1280 units (or 2560 18650 cells) in 27 modules each configured as 3s16p, totalling 115 kg of bare cells plus module overhead, plus enclosures.

It's actually 26 2/3 modules, so perhaps 81s16p Swing units (or 81s32p 18650 cells) for 300 volts (nominal). That's 1296 units (or 2592 18650 cells) in 27 full modules.

Total volume would be about 60 litres, which doesn't seem unreasonable at all. The challenge is that it is a lot more difficult to pack a couple dozen rigid bricks than the same volume of liquid in a tank which can be shaped to conform to the available space.

I wouldn't expect all of that to fit in the front with the motor and controller, and the space used by the fuel tank is not going to conveniently fit the modules. I'm looking forward to seeing the pack design.

See less See more

tom3141

Discussion Starter · #32 · Apr 1, 2018

They’re actually in a 6 x 8 array currently connected 6s8p so I just need to reconfigure to get 3s16p within each module. Although they are almost identical in size to two 18650 cells apparently they are actually one oval shaped cell. Someone on a forum (I can’t remember which one) took a cell apart to find this out.

The external dimensions of each module with the plastic casing included is 285mm x 180mm x 80mm.

I have 28 modules in total but I’m just going to have to see how many I can fit in. I only need a range of 40 miles but I want to put as many in as I can so that I can use as little of the capacity as possible in normal use.

The motor is rated at 208V AC which would be a 293V DC battery pack voltage. That’s why I thought 27 modules giving 300V nominal would be the maximum I would want. A slightly lower pack voltage wouldn’t be the end of the world. I think even 24 modules would be ok at 266V nominal (and around 18.5 kWh) if space is an issue.

tom3141

Discussion Starter · #33 · Apr 5, 2018

I had a lot of trouble trying to weld up the sills and floor at the weekend. It may just be my lack of skill with a welder but the steel is so thin on the Cappuccino that I'm finding it impossible to weld. I'm going to reassess it at the weekend but I have even started to conisder whether this is the right car. I don't want to patch it up badly now and put all the work into a conversion only for it to rust to bits in a couple of years. Cappuccinos are terrible for it, mine isn't too bad compared to some but it's not as good as it first seemed. I'm going to try to take the rear subframe out at the weekend so that I can double check for rust on the bodyshell above it. If there is any serious rust there that I haven't already spotted it might be game over for the shell.

Before purchasing the Cappuccino I had considered a kit car or scratch built. I'm half considering this again using everything out the Cappuccino other than the bodyshell. However, reading through the IVA (Individual Vehicle Approval) manual has scared me off a bit. The section on EVs is worrying. Have any of you UK based builders got an EV through the IVA? It seems that it has to be tested against the ECE R100.01 standard which sounds pricey. Also, on this note, for a normal EV conversion in the UK, is it still the case that you just have to send the V5 off with a change of fuel/engine and then get it MOT'd? Or is there an EV test/inspection that it must pass?

I'll probably end up sticking with the Cappuccino, I think it was just an overeaction to laying under the car all day attempting to weld and not getting anywhere! The other option is getting a professional in to do the welding. However, I think it would need to go to a proper car restorers rather than a local garage/bodyshop. They are going to want to strip it right down to a shell to dip or blast it before repairing properly. I don't think replacement floor or sills are available so it would need repair panels making from scratch. I don't know if it's going to be worth the cost.

See less See more

Duncan

· #34 · Apr 5, 2018

Hi Tom

It's a small car and you are stripping it down - have you thought about making a "rotisserie" for the shell so that you can weld across and down rather than up

as far as future rust is concerned paints are incredibly good these days - but the most important coat is the first one

Sills/floor panels

Back in the day the process was not to buy a new sill but to bend a bit of welding wire to the required shape and the sheet metal man would then bend the sheet to match your template - I can remember mini "sills" that were so wide we welded them to the centre tunnel

brian_

· #35 · Apr 5, 2018

tom3141 said:
Before purchasing the Cappuccino I had considered a kit car or scratch built. I'm half considering this again using everything out the Cappuccino other than the bodyshell.

Since it's unlikely there's a kit in existence designed to use Cappuccino components, this would presumably be a scratch-built (although potentially following an existing general frame and body design, or a general pattern such as the "LoCost" style). Are the Cappuccino components really what you want in a scratch-built (maybe they are, as they would be light, have a sophisticated design, and use modern parts), and is that the best way to get value out of the car you have?

MalcolmB

· #36 · Apr 6, 2018 (Edited)

Hi Tom,

I spent many hours last summer repairing the sills, inner arches and floor rails on my son's MX5, so I know how frustrating a task it can be. It does give you a sense of achievement though when it's finally done.

You probably already know this, but here a couple of things I found useful, assuming you're using a gas MIG welder.

It's essential to cut back to clean metal, or at least metal that can be ground back to a clean surface without becoming too thin. Grind back paint or rust at least a centimetre from the edges to be welded.

Don't try to make continuous seam welds. Make a series of overlapping "spot" welds.

If the existing metal is so thin that it still keeps burning back, it helps to use lap joints where possible. Make patches that lap underneath the existing metal. That way the new metal will draw some of the heat away and prevent burning through. The easiest way to make these patches is with a joggling tool – you can find them for as little as £20 on ebay.

tom3141

Discussion Starter · #37 · Apr 6, 2018

It's a small car and you are stripping it down - have you thought about making a "rotisserie" for the shell so that you can weld across and down rather than up

Yes, I've considered that - it might be the way to go if I decide to stick with the Cappuccino.

Since it's unlikely there's a kit in existence designed to use Cappuccino components, this would presumably be a scratch-built

Yes. I've always fancied designing a car from scratch. I do a lot of design using Solidworks for my job so have the tools to do it. I might even have a go at a design just for fun even if I don't proceed with it. Another reason I'm tempted by the scratch built route is that I can design it around my components. I wouldn't have all the issues trying to cram the motor and batteries into spaces where they don't fit.

Are the Cappuccino components really what you want in a scratch-built (maybe they are, as they would be light, have a sophisticated design, and use modern parts), and is that the best way to get value out of the car you have?

This is bascially what I'm weighing up at the moment. As I said I want to have a proper check over the entire bodyshell once the subframes are out. Then I'll have to decide how I get the most value out of the car. If the rust I have already found is all there is, then it would probably be silly to scrap the shell. However, the components would be really nice for a scratch built car. All the important bits are bolted to the subframes so it would be relatively easy to build.

It's essential to cut back to clean metal, or at least metal that can be ground back to a clean surface without becoming too thin. Grind back paint or rust at least a centimetre from the edges to be welded.

Don't try to make continuous seam welds. Make a series of overlapping "spot" welds.

If the existing metal is so thin that it still keeps burning back, it helps to use lap joints where possible. Make patches that lap underneath the existing metal. That way the new metal will draw some of the heat away and prevent burning through. The easiest way to make these patches is with a joggling tool – you can find them for as little as £20 on ebay.

Thanks for your tips Malcolm. I think one of the problems I've had is that I haven't cut enough metal out. I cut out all the actual rust but the edge of the floor I'm trying to weld to is too thin. It's ridiculously thin metal from the factory so any rust at all makes it paper thin.

I have made up the patches already. I'm doing lap joints as well but still burning through the floor on my MIG's lowest setting. I've also had trouble getting the two overlapping pieces of metal clamped up nicely, any little gaps and it is impossible to weld.

Part of the problem is that I was not expecting to have to do this welding when I bought the car and I'm desperate to get cracking with the conversion. If I decide to stick with it and do the repair then I'm going to have to accept that it's going to take a while to do properly.

See less See more

brian_

· #38 · Apr 6, 2018

tom3141 said:
I've always fancied designing a car from scratch.
...
Another reason I'm tempted by the scratch built route is that I can design it around my components. I wouldn't have all the issues trying to cram the motor and batteries into spaces where they don't fit.

...
All the important bits are bolted to the subframes so it would be relatively easy to build.

While I hope the body repair works out, this sounds like a great scratch build.

I did a quick web search to see the Cappuccino chassis components, and they do look nice for integration with a custom tube frame, at least at the rear.

If building your own body and tubular steel frame, you might even be able to fit a small complete drive unit (motor with transaxle) into the rear.

See less See more

tom3141

Discussion Starter · #39 · May 2, 2018

So I've decided to stick with the Cappuccino. It seems currently the regulations are fairly straightforward for a scratch built EV but they are expected to change in the near future. If I started a scratch built and didn't finish before any new regs come in it would cost a fortune to make road legal.

I've found someone who can do the welding for me so I'm going to pay him to do it. It will mean that I can get cracking on the conversion which I'm desperate to do. He can't fit me in for a few weeks so in the meantime I'm planning to confirm the mounting points for the motor and battery boxes.

I did some measuring up at the weekend and I think I can fit 12 battery modules in the engine bay in front of the motor, 10 modules in the boot, and 3 modules in the fuel tank area. This will give me 25 modules which should be enough. I'm going to design some battery boxes and double check these fit in the space available.

brian_

· #40 · May 2, 2018

tom3141 said:
They’re actually in a 6 x 8 array currently connected 6s8p so I just need to reconfigure to get 3s16p within each module. Although they are almost identical in size to two 18650 cells apparently they are actually one oval shaped cell.

tom3141 said:
I did some measuring up at the weekend and I think I can fit 12 battery modules in the engine bay in front of the motor, 10 modules in the boot, and 3 modules in the fuel tank area. This will give me 25 modules which should be enough.

So 25(3s16p) Swing cells, for 75s16p overall, for 278 V (nominal) at 70.4 Ah and 19.6 kWh (nominal). Sounds promising.

21 - 40 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.