I’ve done a few sketches on some common motorcycle frames
Ideally I would want to cram at least 20 kWh, not that easy given that the only one with something near are the Enégicas, giving almost 200 km range on highway
Here’s some measurements for those interested. The last two photos shows the outer distance between the two shaft holes for the half shafts. There is a decent difference here so that means I will need at least 1 different half shaft depending on where the transmission will be mounted. I need to get the old one out so I can see how the mounts will work. It’s looking like there will be a decent amount of welding though unfortunately
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Before you put that monster in, will you verify that it works ok?
I want some videos 
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Absolutely! Once I’ve got the main parts there will be plenty of videos showing how it all works. Its gonna take me a couple months to get everything so bear with me, but the end result should be cool
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This looks like an interesting project for sure! I like the idea of a manual transmission coupled with the electric motor quite a bit.
Bookmarking, since prius motors are cheap and might be a fun microcar propulsion device…
A couple points of interest:
I’m not familiar with the laser, and it’s been a while since I’ve played with something of this vintage, but I suspect the prius’s 6.5k rpm likely meshes well with the original tach, and that the tach/(speedo?) output is a convenient cable coming out from the top of the trans to your cluster.
From what a coworker that formerly worked in PHEV batteries tells me, most OEMS opted for cell blocks of 14-16S (iirc, tesla excepted) which were then strung together, have you given much thought into your BMS setup?
From the discussion on the SPIM08HP cells, it seems that they sag pretty quick, so you may need a larger initial pack for testing, particularly as the Wh/km consumption is going to be orders of magnitude greater than our standards.
I would have mentioned Chevrolet Volt batteries as a good price/performance option, but those modules have the packaging issue you’re trying to work around
The transmission plate adapter looks like a good candidate for a waterjet, possibly secondary processing with a mill to clean up the mount holes if they’re on shoulder bolts/dowels. This should be cheaper than finding a place to EDM your profile, but that may be worth checking for a comparison, particularly as you’d lose a good deal of profile tolerance on the back side at thicker dimensions with the waterjet.
I don’t have access to one anymore, but when I had needed unobtanium (2d) parts, I just scanned them on the xerox, loaded into corel/illustrator and auto traced the outlines. a bit of minimal cleanup if I needed something with a dimension better than +/- .5mm and I had my new gasket or w/e to laser/waterjet.
Your local EV group will probably have far more valuable input, so I’m interested to see what they have to say about some of the roadblocks.
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Lots of useful info here, and I love having discussions about this project so keep it coming.
I’m no longer using the original transmission as the Prius transaxle contains everything I need. The old tranny will be coming out this week depending on the weather.
This is true of the old transmission, not sure if the new one uses a manual speedo cable still or if it’s electric. I am scouring the Prius service manual to determine this. The document is over 4000 pages long and not in order so taking me some time to get through it. If the Prius transaxle does not have a manual cable, then I will use a laser to figure out the final drive RPM then drive a small motor in the instrument cluster that runs the speedo at the correct speed.
Honestly BMS is pretty low on my list right now. When I start, as the build is being tested and stuff, I was planning on getting a few of those charge only BMSes from Ali that let you daisy chain the modules for much larger series packs. Once I have made final decisions regarding batteru s I can start to figure this out. As long as I have a way to check each series voltage I’ll be happy. I don’t plan on adding extra gauges and stuff like DIY EV builds usually do. I want to keep the original look and feel of the stock cluster.
My issue for batteries is that I’m in Australia, where we don’t really sell EVs besides Tesla (just seen my second ever Leaf on the road today). I have been looking at the SPIM08HP for a couple parallel groups (at around 50S for 200v) which would be located close to the battery, and then I would have a bunch of high capacity lower amperage cells. This method is currently employed by @MoeStooge in his race boards successfully. If my testing shows that this won’t work then I’ll either just use SPIM08HPs. Those cells can be bought and shipped to Australia, which I’m currently having sorted. BatteryHookup sometimes has some Leaf (22kwh) packs for only $1600US but due to weight (650lbs) it would be nearly impossible to get it shipped here without going bankrupt.
As far as I can tell our local group no longer exists. Updates haven’t been posted to their website for like 18 months. The statewide EV group also was unable to run their yearly EV Expo this year due to lack of interest for t group. I’ve found as I delve further into this niche that there really isn’t anyone interested in it, which is disappointing. We live in the most exciting time for electric vehicles now is a great time to go out and build your own.
I’ve noticed you know a lot about materials technologies, I was wondering what you think would be the best way to design mounts for the new transmission? It’s bigger and heavier than the old one so obviously I wanna make it as strong as possible. I’ve never welded before but am willing to learn if it can be done fairly easily
My reading comprehension is a bit better in the light of day 
Removing the old trans will certainly save a good amount of weight and package space. My only check in that case is that you’ve verified the final output rpm of the new transaxle to the laser’s original first and fourth/fifth gear to make sure you have enough starting torque along with your top speed.
otherwise, it may be prudent to keep mg1 and mg2 independent to take advantage of the plantery system.
You might have already seen this, but it’s a site that I found informative a decade(!) ago: http://eahart.com/prius/psd/
though I’ll need to dig to get the flash player functional to play with the sliders…
by 2000, I’m guessing that toyota moved to the wheel hub mounted speed encoders, the rpm of the motors should be something that you’d be able to read from the motor controller itself like how we read out erpm on the vesc (how open and accessible it is for you to do that is another matter (I still need to delve into the controllers you mentioned)) in the end, I’m guessing the easier option will be to use the laser (or maybe a simple hall encoder) and a servo like you mentioned.
I just went back to your picture of the IP and noticed that the cluster omits the tach, so only one output to deal with in any case.
I wasn’t aware of the ali chainable BMS, but that sounds like it has promise. I’d still want a way to read out the min voltage of any of the P-groups though, just because the sheer number of cells compounds failure incidence. Maybe using the fuel gauge for overall voltage/coulomb count with the option of a toggle to flip to read out minimum cell voltage? Or recessing a voltage readout behind the existing battery emergency light? Some sort of pack health monitor in any case…
The modularity is definitely what makes it a cost effective setup. A sort of charge and ride on a larger scale, I guess.
…that’s unfortunate. as good as the internet, video overviews and whatnot are, there’s still a lot of value in the tactile interface that you can get hands on with someone else’s project. Nothing to be done about it, just a lament on my part.
Looking at the wikipedia entry for the laser, the E series’s iron block, plus the transmission must be heavier than the prius’s aluminum housing+steel stator(s)?
I think as long as you can secure the new motor transaxle assembly, countering the hanging moment arms, you should be ok.
I’d definitely try to use as many of the existing motor and transmission mount points as I could. that way you can keep/source oem dampers to avoid stress risers and fatigue on the sheet metal in non structural areas (I think the weight in the fuel tank will be a greater concern there…)
Look at how the mounts are setup to see if it’s likely that the engine itself was a stressed member that formed part of the structure to inspire your spaceframe.
Beyond the existing motor mounts, possibly a “K-brace” between the strut towers and firewall?
In any case, welding is a great skill, I highly recommend picking it up for the doors it opens up for you.
If you ask around, you’ll probably have most people pushing you towards TIG for the control you get.
Since I don’t have that finesse, I’m more fond of MIG since it’s a few less things to coordinate about while you’re casting lightning and slinging molten steel. Both are fairly quick and learnable to the point that your work is structural, if not aesthetic, though, so that’s ultimately up to you. You’ll get more respect for knowing TIG . 
Look into tube stock that racers around you would use for their roll cages. CAD would naturally be best, but again, as a seat of the pants person, I think you could get away with a lot of hand measurements and test fits. (besides, getting CAD of a 36 year old vehicle sounds implausible without paying far too much money for a cloud scan)
Make sure you form triangles with your joints, and your biggest challenge will be in cutting the tubes so they mate cleanly and you’re not trying to stitch them together with weld.
…this is where you’ll curse not having CAD as you go back and forth grinding fishmouths into tubes to guess and check fit
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So the Prius Gen2 transaxle has a final drive ratio of 4.11, and the KB Laser final drive ratio is 3.77. I’m unsure if this will be problematic but considering MG2 is rated for 400nm and the Laser’s ICE is rated for 92nm I shouldn’t have any torque issues.
Due to the DIY nature of the controller I’ll be using, I don’t think it has any sort of output designed for reading RPM, but in saying that I know the main connector for the inverter has some spare pins and the project is open source so I could always just create the reading myself. Servo on the speedo might be easier honestly
For the fuel gauge the plan will be to use this: https://www.zeva.com.au/index.php?product=126
Its a simple product and has an analog voltage output which means its perfect for my IP. For voltages I do plan on having some way to read that but hopefully will either be hidden or very discreet, haven’t decided on this yet
I’m not sure on the exact number, but I should have at least a couple hundred pounds spare for batteries, but I will be weighing the empty shell at a weighbridge before the new transaxle goes in so I know how much headroom I have
Regarding the welding, I’ve always wanted to learn and think it would be a great skill to have. This project is the perfect opportunity but I will definitely need some practice. I’ll have to go out and buy a welder and some tube steel and get going!
I wanna make sure that the transaxle is properly supported, so I’ll probably use the original transmission mount with some extra support structures coming off another structural source. I’m gonna have to have a harder think regarding batteries in the rear. I have considered cutting out the floor of the car where the fuel tank is and essentially extending the area at the back of car that is lower and using that for batteries. That will come in the future I think
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This is the Prius Gen3 Inverter/Converter
(Discourse has a bug that fucks the rotation)
Here we have a package about the size of a large toaster, which is capable of outputting potentially hundreds of kilowatts of power. Not only does it contain two inverters, there is also a boost converter which takes the 203V battery and boosts it up to the 500V that the motors are capable of using. In the bottom there is also a DC-DC converter that is capable of 100A+ at 14.2V. Inside there is lots of complicated circuitry that goes over my head but I do know that it uses IGBTs to achieve its power ratings.
Here you can see the main DC battery connection, as well as the multipin Ampseal connectors which are really cool because they are waterproof. I am unsure of where these connectors will be going yet as the current setup for using this hardware doesn’t have defined things like connectors yet. This will come in the future.
This unit is watercooled as it is very high power but due to its size and very little thermal mass. Even when doing bench testing it is recommended that you use even a simple 12v pump and water because otherwise it’ll burn up very quickly.
Toyota’s engineers have really hit a jackpot here as this is a super powerful little unit and its basically indestructible. It supports battery voltages of ~120V-~400V which means a broad variety of batteries can be used. When trying to pump too many amps into this thing, it won’t blow up, it’ll just shut down. When trying to overheat this thing, it won’t blow up, it’ll just shut down. It handles faults gracefully which means that this should be perfect for me as someone who blows stuff up regularly.
I’m about to do a teardown of this thing so if anyone wants photos of anything in particular just let me know
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Damien also released a new board revision yesterday for the Prius control board, and he specifically added the required components for me to be able to run both MG1 and MG2 in parallel, hooray!
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That seems pretty clever, kind of a reimagination of a clamp style DC ammeter. My knee jerk was that it seemed expensive, but I haven’t seen anything else that handles DC current, particularly with the convenient outputs.
I definitely support the the impetus and learning welding, so show off your test pieces and skill development here too.
You might be able to reinforce/replace whatever subframe was present, since I’m guessing that was stamped steel, so a tube structure should give you some more strength down below.
The rear will be more difficult for sure. Besides the strap for the fuel tank and hangers for the exhaust, you’ll have to look around for hard points. I’m not sure what the suspension is back there, a torsion beam (the era makes me uncertain, but being a mazda, possibly…)? Tying the two sides together would make for a humorous driving experience, but maybe not what you’re looking for 
I was impatient watching the referenced youtube videos, so I’m interested in the teardown for sure. the 500v step up seems particularly interesting.
Good stuff!
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So I just got the old transmission out of the car. Honestly wasn’t that hard, jiggling the axles put was the hardest part.
Seeing the engine bay without the transmission allows me to visualise better how I want to do things:
Here I have circled where the transmission mounted in red, and the engine in green:
In this image I show how the transmission is currently mounted, horizontally with the axles at the back, in green I have shown possibly how the new transmission could be mounted, vertically with the axles at the bottom:
In this image I show in red possible where some box steel could be used to reinforce the transmission:
Here is some closeups of the old mounts:
Here you can see the old transmission in comparison to the new one:
The current fuel tank simply bolts into the body of the vehicle, so I think I will just reuse the tank and bolt it back in to keep things easy for me, at least for now.
That video of the transaxle I have referenced like at least a dozen times in the last few weeks and I’m sick of watching but old mate does such a good job of explaining things. I will be starting the teardown tomorrow as it’s raining so I’ll be stick inside all day. I tried today but I have up quickly due to the heap of black silicone holding the two halves together
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One funny thing I noticed was when I was removing the speedo cable, on the end was a plastic gear. I swear I remember a heated discussion about not using plastic gears in our esk8 gear drives. This vehicle has 140000kms on it with no broken gear…
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A speedometer drive is not really transmitting any power.
A spiral gear like that has very little load on it and will wear very slowly unless something jams up in which case you want it to fail to save the transmission.
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I’m well aware that the forces on the speedo cable are not comparable to any sort of load bearing gear. Was simply a joke, I forgot the /s
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I still can’t believe how clean that chassis is… It’s like the car’s never seen salt …or rain
proposed transmission positioning looks good to me. The existing mount points look like they’re well triangulated to support the mass too.
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Yeah its very clean, I expect it to get a little worse as I unfortunately don’t have the undercover space that it deserves
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Just finished the teardown of the inverter. Not a full teardown, but I needed to figure out how to get into the enclosure because I will need to replace a board eventually
Here under one of the top covers is access to one set of 3 phase connections as well as an interlock circuit that will stop the inverter from being able to run without the cover on
Underneath the bottom black pan cover is the DC-DC converter (I think)
Underneath the top lid is the circuitry for the current sensors. Here you can see a section that is covered by silicone of some sort. Good way to waterproof
And here is the star of the show. The top PCB is the control and interface circuitry for everything and the one underneath is the power stage PCB. Under that is the IGBTs and then cooling fins and a separate cooling channel for the water cooling. This top board will be the one that I have to replace with Damian’s one
PCB is covered (mostly) in conformal coating. That has to keep Brian happy
This is the main Ampseal connectors which I think I need to remove from this board and put on the new board when I get it eventually
Here you can see some blurry stuff, maybe cooling fins
This is the main connections to both the MG1 and MG2 power phases, you can see they are neatly labelled
Here is some photos from Damian of a mock-up he did of the board
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