[DRIVING] 1992 Toyota Previa with Leaf stuff and lots of Tesla batteries

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[DRIVING] 1992 Toyota Previa with Leaf stuff and lots of Tesla batteries

Post by celeron55 »

Story time!

In 2014 I bought a 1993 Previa because I thought it was cool. When 2016 came about, it developed a cylinder head issue and I bought another one, a 1991, because it was cheaper than a cylinder head would have been. That one got totaled in an accident in 2017. Then later in 2017 I found the third one, a 1992, for even cheaper, so I had to buy it.

They're great minivans. Really the only issue is the terrible fuel consumption, and even that is kind of offset by their inability to break in any major way. Certainly you can't get stranded in one, it's always just the emissions test stuff and slightly loose joints that gets 'em. The design is absolutely timeless.

At that point in time I realized if you're smart about sourcing them, Tesla Model S battery modules had gradually gotten pretty cheap. I could afford almost a full pack and still have money to eat.

So, a few months into the year 2018 I had modelled the underbody of the Previa in FreeCAD and had various plans for battery and motor placement. I owned a Leaf gen 2 motor, inverter and PDM and had 12 Model S modules stacked on my living room floor, had reverse engineered the inverter protocol and published it, I had working communication with the BMS in the battery modules, I had some heavy duty welding cable with orange double insulation, I had two GV200 contactors, a big ceramic fuse, some 1/16" copper sheet for bus bars, cable glands, I had an assortment of coolant pipe fittings, a coolant heater waiting to be modified, a plan for the power steering, a plan for a transmission input shaft adapter, a plan for supporting the transmission input shaft by precision drilling the end of the motor shaft by using the motor itself as a lathe using a 60° drill bit. I had cleared out enough of the bureaucracy for it to not be a likely issue anymore.

Then, having a plan and most parts, it was mostly a matter of just putting them together, sorting a few problems as they came. I got it driveable by mid summer and registered as an EV just before winter.

I would do this all day all over again for years to come, but the problem is the end result isn't worth even the sum of its parts, so if I'm to make another, I'm going to have to be creative, as a vehicle with an affordable range is kind of useless in these parts of Finland and most people can't afford the upkeep of multiple vehicles.

So, the end result is a 1992 Toyota Previa with
- 12 Tesla Model S battery modules installed in place of the second row seat inside a steel frame with polycarbonate and aluminium-plastic composite sheeting,
- a gen2 Leaf motor driving the original manual transmission without a clutch, using a 25mm aluminium plate and a machined piece between two clutch plates to mate the motor to the transmission,
- a gen2 Leaf inverter installed separately from the motor with no internal modifications,
- a gen2 Leaf PDM, heavily hardware modified (it's what we call "lobotomized"), working as the AC charger, the DC-DC converter, providing the CHAdeMO contactors and switching the coolant heater on and off with an added internal contactor,
- a DIY inverter controller talking with the inverter, measuring the signals from the original throttle position sensor from a throttle body carcass and generating the instrument cluster signals RPM, fuel gauge and low fuel light,
- a DIY BMS controller talking with the Tesla modules and the system CANbus and controlling a main contactor, a pack split contactor and a precharge contactor,
- a DIY "coolant controller" controlling the solenoid valves, coolant pumps, radiator fan and measuring the coolant heater temperature,
- a DIY CHAdeMO controller controlling CHAdeMO things (not perfect, but works with most chargers),
- an Opel/GM power steering pump, in this case a CANbus variant that I also reverse-engineered (just tell it to 0x110 11 11 11 11 11 11 11 11 and you're golden - it's a stupid little thing),
- a VW vacuum pump and a GM intake pressure sensor with a touch of electronics to make vacuum for the brakes,
- a DIY central display for energy, power, charger status, coolant temperature and other readouts and
- an Eberspacher D4WSC heater for the 9 winter months around here (heating that cabin using batteries would be absolutely silly on long trips)

Every module communicates on CANbus.

Additionally it now runs the gen3 prius 3-phase type 2 on-board charger experiment.

Money statistics: The base vehicle value was about 3% of what I spent on the conversion, and out of it all, battery modules make up about 70%.

It's quite fun to drive and it can take a 200km trip fully charged in all except some winter or headwind conditions. Currently it's averaging about 230Wh/km. The battery pack would be rated 63.5kWh by Tesla, but at this point in its life it's something like 56kWh.

Curb weight is now 1950kg and it can carry 5 passengers. Originally 1680kg and 8.

It's rated to tow 1600kg, which is respectable for an EV. Energy consumption towing or non-towing is pretty much equal to the Audi e-Tron, which is pretty good considering they weren't even dreaming of proper EVs when this vehicle was designed and built.

Also, I don't have flat belly panels on this. Please go on and make your estimates about the Wh/km difference those would make and cite your sources. I might add them if you convince me.

This gallery has photos of almost every step of the making of this:

http://packages.8dromeda.net/evprevia/gallery/

This conversion consists of pretty run-of-the-mill parts if you don't count the electronic wizardy. Just develop an accurate drilling strategy and find some goof with a lathe and you'll have your motor adapted.

If someone is bored, feel free to copy any of those photos onto this forum for safekeeping.
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Re: 1992 Toyota Previa with Leaf stuff and lots of Tesla batteries

Post by celeron55 »

More random photo attachments as you can only attach so many in one post.
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Re: 1992 Toyota Previa with Leaf stuff and lots of Tesla batteries

Post by johu »

Nice, I like minivans (Touran you already know, I also have 97 Sharan - Diesel :oops: )
That blue rack holds the full 63 (56) kWh?
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Re: 1992 Toyota Previa with Leaf stuff and lots of Tesla batteries

Post by Kevin Sharpe »

johu wrote: Thu May 07, 2020 8:49 pm That blue rack holds the full 63 (56) kWh?
12 x 5.3kWh = ~63kWh 8-)

http://packages.8dromeda.net/evprevia/gallery/#105
This is a personal post and I disclaim all responsibility for any loss or damage which any person may suffer from reliance on the information and material in this post or any opinion, conclusion or recommendation in the information and material.
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Re: 1992 Toyota Previa with Leaf stuff and lots of Tesla batteries

Post by celeron55 »

Tesla batteries are crazy good in storing energy. The only problem is you need a lot of them to get power out of them. Especially at winter even that much is very sluggish as I limit motor power in such a way that the cells never go below 3.15V.

Also, the Touran is almost a compact hatchback compared to the Previa. Sharan is getting close!
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Re: 1992 Toyota Previa with Leaf stuff and lots of Tesla batteries

Post by celeron55 »

I just published a video of a reasonably long trip and some introduction at the beginning. For this trip I usually choose the converted Previa over my diesel van even though it's a bit more hassle.

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Re: 1992 Toyota Previa with Leaf stuff and lots of Tesla batteries

Post by johu »

Familiar motor sound.
Confused by the number of charge ports ;) So one single phase under the hood powered by PDM, a 3-phase Prius experiment behind the fuel filler door and also chademo somewhere?
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Re: 1992 Toyota Previa with Leaf stuff and lots of Tesla batteries

Post by celeron55 »

Yeah, three different charge ports. Each charger is basically just a development test version with weird unfixed problems so sometimes it feels I need a fourth one... :mrgreen:

EDIT: Let's list the problems with each:

Type 1 (PDM, about 3kW): I forgot to implement the CP resistor switch so many charge points that require it won't work. I also forgot to implement the input precharge relay control so it sometimes flips the circuit breaker. Difficult to remove from the car and I didn't document much so quite an effort to add the missing features.

Type 2 (Prius gen3 inverter thing, about 18kW): The circuit breaker inside the charger can switch off when I drive into potholes and it's really difficult to take off the car, no other way to switch it back on. Also, there's no way to know whether it's on or off without having a 3 phase outlet at hand. Because I didn't connect neutral anywhere, it does nothing on single phase input, doesn't even see it. It's a bit of a dice roll due to these facts.

CHAdeMO (DIY controller, port on the driver's side under the hood, 125A@300V=37.5kW): When it worked, it didn't work with some chargers for some obscure reason. But now it doesn't work with any chargers and I haven't yet diagnosed why. To begin, I think I should check for broken wires.
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Re: 1992 Toyota Previa with Leaf stuff and lots of Tesla batteries

Post by celeron55 »

Some updates on this conversion:

CHAdeMO fix:

I fixed two problems with CHAdeMO: A contactor coil wire was broken in the wiring harness, and I managed to fix the communication bug in my code. More info about the bug here: viewtopic.php?f=11&t=32&p=29134#p29134

Cruise control:

I had set up a cruise control button on the dash for a long time already, but until now it did nothing. I wired up the brake pedal to my VCU and did some coding and PID tuning and now cruise control works quite well.

Road trip:

I just did a 10 day 1900km road trip. Almost all charging was via CHAdeMO. Only some 42kWh or so using a granny cable and maybe 2kWh of 3-phase type2 while queuing for a CHAdeMO charger. Average energy consumption was pretty much smack dab 200Wh/km, total energy consumption ending up being about 380kWh. Mostly speeds 60km/h, 80km/h and 100km/h.

Outside temperatures were very high, up to 31°C, but I could always charge some after driving and not once had to wait for the battery to cool down. My battery temperature limit is 50°C. Once that was reached I set off again and continued driving until I had to charge again.

There were a couple of 400km daily drives and one 500km.

Attached is the graphs of the final 500km drive. Outside temperature was around 20°C. It was about 6 hours of driving and 3 hours of charging. I started at about 50% SOC and didn't shut down the car at any point.
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Here's a photo of charging at Hartola (in Finland, obviously):
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Cruise control button at the left:
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Re: 1992 Toyota Previa with Leaf stuff and lots of Tesla batteries

Post by johu »

Greetings to homebrew CHAdeMO travellers!
I have a bit of rapid gating. First charge is usually fine. Charged 25 kWh today and temp went from 23 to 46°C! Limit is also 50°C. While driving I loose about 15°C till the next stop so that usually throttles towards the end.
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Re: 1992 Toyota Previa with Leaf stuff and lots of Tesla batteries

Post by celeron55 »

I saw forum user mfox celebrating their 20 000 km milestone, so I'll do my own:

This conversion has now clocked 60 000 electric kilometers.

No expensive parts have needed replacing, and performance of the battery and drivetrain are just as good as 60 000 km ago.

I did add an Outlander heater this winter. It's a nice addition, making the Eberspacher diesel burner mostly unneeded, aside from certain trips that stretch the range capability.

This conversion has turned out to be a very good investment.
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Re: 1992 Toyota Previa with Leaf stuff and lots of Tesla batteries

Post by Ev8 »

That’s pretty awesome well done
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Re: 1992 Toyota Previa with Leaf stuff and lots of Tesla batteries

Post by celeron55 »

I got the opportunity to swap the 5.3kWh nominal Tesla modules to 6.2kWh nominal ones, so that's what I did.

The modules have a different coolant port design, which forced me to re-do the coolant system for the battery too. The original design had too many modules (3) in series, hurting the cooling/heating capability way too much. The coolant system now takes up more space so I have some finishing to do as it didn't quite fit in the original space allocated for the system.

The modules weigh about 10% more and should have about 20% more capacity, assuming they're at the same SoH. The car is sitting again quite low at the rear with the extra 30kg. I probably should change the other rear spring finally...

It took about 3 long back hurting days:
- 1 day to pull the new modules from the Tesla pack
- 1 day to pull the old modules from the Previa
- 1 day to design the new coolant system and install the new modules
- And some day it'll still take 1 day to finish the cover/trim sheets for the battery and do some calibration work to the BMS and dash.

It looks practically the same as before, except for the cooling system, so here are a few photos of that before installing everything. The packaging design of this pack is incredibly tight. I don't know of any other car where you could fit this layout.

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Re: 1992 Toyota Previa with Leaf stuff and lots of Tesla batteries

Post by whereswally606 »

Love this build. We hired a previa to go camping from bumble campers in the uk. My boys 4 and 5 at the time loved it as the car looked like a bee.
I really like the photos of you charging next to the very pricey oem evs, makes me smile.
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Re: 1992 Toyota Previa with Leaf stuff and lots of Tesla batteries

Post by celeron55 »

Motor shaft adapter decided it wants some fresh air.

I'm going to just replace the motor side clutch disc part for now. Next time it goes I'll have to buy a properly fitting spline and re-engineer the adapter as the meat in the motor shaft isn't going to be enough for a new clutch disc next time. It lasted for about 70 000 km.
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Re: 1992 Toyota Previa with Leaf stuff and lots of Tesla batteries

Post by celeron55 »

Long story short: I was planning a road trip around central Europe with the Omega, but just in the final days before the trip it started acting up and killing vital components, so I set up CCS in the Previa instead, got new tyres and the paperwork and set it up as a mini camper all in like 2 days and set off with this thing instead.

So, I am on the road trip now. We crossed the German border yesterday after about 1700km of driving in 3 days. We're headed towards France at a slower pace now.

If anyone would like to see the Previa and chat with me in person just let me know. PM me or I won't get notified. Now around north west Germany, later this week further south west in other countries and in the upcoming weeks in various southern places.
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Re: 1992 Toyota Previa with Leaf stuff and lots of Tesla batteries

Post by celeron55 »

After more than 3000km of driving, we have reached the alps.

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Re: 1992 Toyota Previa with Leaf stuff and lots of Tesla batteries

Post by johu »

Incredible! So charging must have worked in Appeldorn
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Re: 1992 Toyota Previa with Leaf stuff and lots of Tesla batteries

Post by celeron55 »

Apeldoorn was the only Tesla Supercharger site that didn't work, out of probably more than 20 so far. We switched to a Tritium Veefil PK by Shell there nearby.

You sometimes have to switch stalls on Superchargers though, due to melted plugs or otherwise inoperable stalls.
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Re: 1992 Toyota Previa with Leaf stuff and lots of Tesla batteries

Post by uhi22 »

I just found this thread, it's really impressive to see that long travels really seem to work :-)
Could you summarize your charging setup and experiences? Do you have ChaDeMo and CCS and AC working in this car? Do you have multiple CCS solutions (pyPLC and BMW LIM) in use? How often did you use which charging interface? What worked fine, and where see you room for improvement?
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Re: 1992 Toyota Previa with Leaf stuff and lots of Tesla batteries

Post by celeron55 »

I'm on my phone so I'll be super brief: My AC chargers practically don't work except under special circumstances, so I don't use them except at home. What I use is:
- My own Chademo implementation (you can find a version of it in the ipdm56 library). It always works. The problems are that 125A is too slow, and chargers are rare. I use it only as a backup, only a couple of times on this trip.
- pyPLC CCS: this is the bread and butter. I charge at 200A, mostly at Tesla SCs because they are reliable and reasonably priced. The only CCS charger known to not work at all is Delta. You have the logs for that. Also Apitronic has the issue that if another car plugs in then charging immediately stops. I have also posted logs of that.
- I couldn't get LIM working but now I see it as basically useless anyway.
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Re: 1992 Toyota Previa with Leaf stuff and lots of Tesla batteries

Post by tapac11 »

Hi

Great work. I was wondering, in a Previa, how do you create the space to get a Tesla drive in the front of the engine so that one can drive the front wheels with a new drive axel. We would want to keep the existing engine and transmission for driving the back axel and add the front Tesla drive. Please advise kindly.

Thanks
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Re: 1992 Toyota Previa with Leaf stuff and lots of Tesla batteries

Post by celeron55 »

I don't think any drive unit can fit in the front. There's no subframe that you could remove and modify and the beefy transverse frame member onto which the steering rack and front diff attaches to is in the way. Towards the rear, the cabin floor is in the way. If you're hell bent on doing that, you will want to cut the cabin floor to fit the motor behind the axle. However, the throttle pedal and HVAC might be sharing the same space.
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Re: [DRIVING] 1992 Toyota Previa with Leaf stuff and lots of Tesla batteries

Post by celeron55 »

I finally removed the Prius gen3 inverter based 3 phase charger. This wasn't working for a long time already and was only dead weight and an isolation fault and a coolant leak waiting to happen. I have no idea why it stopped working and don't really care. Good riddance, as the car still has 3kW AC, Chademo and CCS.

I need to do a bunch of suspension and brake work also. I had to start by removing this one, as it was getting in the way of supporting the car while having the lower control arm removed.
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Re: [DRIVING] 1992 Toyota Previa with Leaf stuff and lots of Tesla batteries

Post by celeron55 »

My recent 2100 km road trip to Sweden brought the odometer of this thing to 389 300 km, meaning it has now travelled 90 000 electric kilometers.

It still runs an ancient version of pyPLC which for some reason doesn't work anymore with Tesla Superchargers which made charging up north a bit of a challenge, AND Chademo appears to also be broken, but we did make it without any extra hotel nights. Besides, the AC charger still doesn't work at public charging points due to lack of proper CP state control, so I'm glad that was the case... Given all this, I don't even want to know what the chances were for us to be able make it all the way. :mrgreen:

The longest day trip was the initial one from Oulu to Turku which is about 650 km. That took about 12 hours. Given a mild weather of below 15°C, it's possible to continuously drive at 80-100km/h and charge at an average speed of about 60kW, resulting in a driving/charging cycle of slightly more than 2:1. Basically drive for slightly more than an hour, charge for slightly less than 30 minutes.

Ideally I'd like something like 3:1 or 4:1, but that would require a stronger cooling system. Given that this already uses the massive stock radiator, I figure that would involve refrigerant. This is why you don't pick a van if you want to road trip - it chugs too much juice which gives too little time for cooling down between fast charging.

Here's a photo of it being parked at the Gripsholm Castle:
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