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EV/hybrid conversion from ICE

2239 Views 22 Replies 7 Participants Last post by  tommyhp2
Hello everyone,

4th gen styling looks very unattractive to me in addition to no 8 passenger beyond LE trim. So I'm thinking of keeping our 3rd gen and doing EV/hybrid conversion. While my question is specific to gen 3 but I think it's applicable to older gen too. I'm looking for some input from DIYers (whom do more than just oil change) or mechanics regarding space and technicality of converting a (gen 3) 2015 FWD to quad EV motors, battery pack, and 600 CC motorcycle engine with gearbox to drive a few alternators. I realize venturing into unexplored territory will have unknown costs (for parts and labor). But seeing options out there, I don't really have much choice unfortunately. With all this (urgent) drive to go green, it seems none of the current manufacturers design their vehicles to be upgradable, within reason, like computers. How much carbon foot print is needed into a vehicle that could be upgradable [1] ... not to mention that styling is very subjective.
  • Space: removing the engine, transmission, exhaust, gas tank should leave plenty of room for 2 rear and 2 front motors for hybrid 4x4 (hoping to implement pseudo locking differential). The battery pack will be installed underneath between the axles and a small pack where the gas tank was. The motorcycle engine driving a few alternators will be in the front where the engine was. There should be half engine bay left for the "frunk".
  • Motor control: I'll probably inquire with AEM if they have or could possibly come up with a solution to control the EV motors.
  • Battery control: I'll probably need to check for CoTS or other means for a reliable BCM/BMS.
  • Vehicle functions: power steering, AC, etc are either done by the motorcycle engine with modifications or converted to electronic counterpart.
  • Ride height: Probably lifted a couple of inches for battery pack, ground clearance for snow and, possibly, off road.
The attached image is the approximate dimensions of the Tesla motor in case I want to use Tesla's instead of other generics. (Courtesy of Tesla Large Drive Unit Dimensions)


[1] "The vehicles are shredded and the metal content is recovered for recycling, while in many areas, the rest is further sorted by machine for recycling of additional materials such as glass and plastics. The remainder, known as automotive shredder residue, is put into a landfill."
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This looks like fun. Are you doing this for environmental or economical reasons?

A “few” alternators aren’t going to cut it, if you’re talking about automotive alternators. Say you have a 130 A alternator. At 15 volts, that’s 1950 watts. 750 watts per HP, so that’s 2.6 HP. So four of these alternators would generate 10 HP of electrical energy. A quick search also shows alternators are anywhere from 55-75% efficient, so you’d need some 13-18 HP from the engine to get 10 HP of electrical output. Most alternators don’t like running at max output continuously either.

To be practical, you’re going to need a high efficiency (90+%) generator sized appropriately to the engine, not a few car alternators.

What about pulling the engine and drive from a crashed hybrid car? May have to look for a suitable vehicle or two and piece it together, but it would probably be a lot less work. The Toyota hybrid drive may be the most difficult, since it maintains a mechanical linkage from the engine to the wheels, and it sounds like you don’t want that anyway. But from what I’ve read the Honda hybrid system and some others use the engine to run a generator which powers the electric motors and charges the battery, with no mechanical linkage. So that’s more along the lines of what you’re looking to do.
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For the sake of accuracy: the Accord and CRV hybrid powertrain does not have a mechanical connection to the wheels only at low speeds, below 45 mph I think (same with the 2nd Gen Voltec powertrain, only that one starts sending some torque from the engine to the wheels around 70 mph).
Thanks, that’s important. I hadn’t really looked into the Honda drive system, just thought I had read that somewhere. If that’s using a mechanical connection for high speeds, it probably won’t be sufficient to convert for this project.
I haven't quite work out the math for the alternators yet but I figured that if an alternator is able to charge the battery or drive the rear wheels in gen 4, what if you have 3+ alternators? In the event that hybrid does not work, I have backup of using Toyota's fuel cell module(s). Just need to figure out the dimensions and placement.
The Toyota HSD does not use "alternators" in the colloquial use of the word. They use expensive, high power density, permanent magnet motor-generators. Yes, the output in generator mode is 3-phase alternating current, which is what an alternator outputs, but that's the only similarities they have. Standard car alternators simply won't cut it. Period. They simply don't have the power output to do what you want.

There are high power, high efficiency 3-phase generators out there (such as the ones used in the HSD), but you're talking thousands of dollars or more. They need to be sized appropriately to match the engine. You'll only need one...but you're going to pay a pretty penny for it.

On a related note now that I'm thinking of it. I read the 4-cylinder atkinson cycle engine in the Sienna hybrid has a whopping 40% thermal efficiency. I would guess a typical 600 cc motorcycle engine may be something like 30% efficient, if even that. This is a massive difference. All else the same (same vehicle/weight/tires/generator efficiency/motor efficiency), at steady state speeds the Sienna can get 36 MPG. The same vehicle with a 30% thermal efficient engine will get...27 MPG. It's doubtful you'd even get that, as the HSD uses a direct connection from the engine to the wheels which helps increase it's drivechain efficiency.

Also since you mentioned environmental reasons, in addition to burning more gas (so more CO2, etc), most motorcycles don't have catalytic converters, so they release much higher amounts of nitrous oxides and unburnt hydrocarbons than a typical automotive engine with a catalytic converter. Obviously you could have a catalytic converter, but your original post mentioned removing the exhaust system, so...

On a related note, you original post also said remove the gasoline tank? How are you going to run your van without a gas tank!?

More and more I think the only way to remotely economically get something that's efficient is going to be to cannibalize an existing drivetrain on a similar hybrid vehicle and use that. It's going to be extremely difficult to get anything remotely as efficient as a DIY build compared to what's already there for anything short of the amount of money that would just allow just buy a 4th gen Sienna and pay someone to custom modify the body to your desired style and add limited-slip or locking differentials.
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The general idea of hybrid that I had was to use motorcycle engine to drive the alternators via gear(s) not belt. For fuel storage, I was thinking of using 2 military grade 5 gallon tanks. For exhaust, I was thinking of using catalytic from small vehicles like Corolla/Civic or smaller. Even though I haven't put the idea in the 3D modeling software, thinking about it there's still too many moving parts so this wouldn't work.
Gear/belt doesn't matter. When you said "a few alternators" I figured you were talking about standard car alternators, and I was pointing out that standard car alternators won't cut it by any means. Nearly all generators output 3-phase AC, so they can be called an "alternator" but nobody does, they simply call them generators.

Alternator came into the car vernacular because early cars (till like the 1970's) used DC generators. It was pulsed DC, but DC nonetheless. When they switched to generators that outputted alternating current they became known as alternators to differentiate them.

I haven't thoroughly thought out my power source yet since I have not able to find the motors of satisfying my need of 300+ hp and 400+ torque combined (75+ hp and 100+ torque per motor) for decent price. I have found a few AC induction motors of similar spec with max ~5k RPM. For highway cruising of 2k RPM (70 MPH in the sienna):
I don't think an induction motor is suitable. Have you looked into the size and weight of induction motors? We use a 20 HP induction motor at work, and that thing is as big as my 100 HP motorcycle engine, and probably heavier.

Doing a quick search, a NEMA 360 frame, 75 HP motor is going to be on the order of 771 lbs, with length not including shaft of 24 inches. There's just no way you could fit 4 induction motors into any sort of passenger vehicle, nor carry the 3000 lbs of said motors.

You'll have to use 3-phase permanent magnet motors for size and weight reasons. This is what everybody uses for electric and hybrid vehicles, and for good reason.

As for 4th gen, my main like of our 3rd gen XLE Premium:
  • 7+1 seating (only available in 4th gen LE)
  • 150 cu ft cargo room up to 1st row (100 cu ft in 4th gen since 2nd row is non removable as quickly and conveniently)
  • Sleek sporty style not aggressive like 4th gen, IMO, or other brands
My point was for the money you are likely to spend, you could buy a 4th gen Sienna, and modify the Sienna body panels, add an 8th seat if you'd like, modify the 2nd row seats to be quick release. If you don't care about airbags in the 2nd row, then you could just fake out the airbag connectors and weld in the track mounts from a 3rd gen Sienna to get the 3rd gen removable, 8 passenger seating.

Modding can be great fun. And people have been making electric cars since forever. I've seen pictures of an electric pickup truck mod from the 70's, with the bed full of lead acid batteries. But trying to build something that someone else has already mass produced on a one-off, hobby scale? There's simple no way to make it on any reasonable economic level.

If this is just a project you want to do, go nuts! Please note I'm not trying to say you shouldn't do what you want. But you seem to be very unaware of what is actually needed, from a technical, time, and money perspective, to get what you want for performance specs.

I'm saying this as someone who has wanted to do all sorts of stuff, and found that in nearly all cases, if something is available off the shelf, there's almost no chance you can make an equivalent product for the same cost, even if all your time is of no account. In many cases, even putting together the parts you need costs more than the off the shelf component.

That said, since your main "sticking points" with a pre-made vehicle seem to revolve around styling and seat arrangement (both of which can be changed), have you considered other options? The Chrysler Pacifica hybrid has more of the traditional "minivan" look, less aggressive than the Sienna. And it maintains removable seats on the 2nd row. The hybrid is not available in an 8 passenger model though (though in the context of this thread, figuring out how to add an 8th seat is one of the easiest things of all those proposed here).
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I had a thought this morning driving to work this morning, inspired by this thread, of what should be one of the easiest ways to convert a Sienna to a hybrid. Take a FWD Sienna, purchase the rear differential, driveshafts, and hubs for a RWD Sienna. Install these and hook a motor up to the differential. Now you can use the motor as a generator when braking to recover energy, and then use as a motor when accelerating to recover this energy and reduce the work and gas used by the engine.

Still won't be anything near as good as a modern hybrid, because you don't have that 40% efficient engine, nor the control system that actively keeps the engine at the 40% mark as much as possible, so it wouldn't improve highway MPG's at all, but it will at least improve city MPGs to some extent.
FYE only (pssst, don't tell tommyhp2) - optimistically speaking, in the next few years we might have a whole bunch of new alternative propulsion vehicles to choose from.
I proposed in a different thread recently that in the next year or two, we'll see a 300+ combined HP PHEV Sienna, based on comparing HP ratings of the RAV4 vs the RAV4 hybrid vs the RAV4 prime, and the fact that Chrysler has PHEV minivan already. The Pacifica hybrid is only 260 combined HP and highway rated at only 30 MPG (after the battery is exhausted), so a 300+ HP Sienna with a highway rating of 36 MPG after battery is exhausted would blow it out of the water, spec wise.
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A 400 cc engine, in one of if not the lowest drag production vehicle you can buy, got 24 MPG at 45 MPH. Almost no cargo space, gets a couple more MPG than the stock 2015 Sienna going 70 MPH, and uses differentials to drive the wheels. It certainly meets all the requirements you've outlined for your hybrid conversion.
I was bored, and wanted to see what my Sienna gets at 45 MPH. So I went for a drive. Unfortunately, it's really hilly here. Altitude is in meters. The data does have timestamps, but it's got data and time in the same column and I was too lazy to get LibreOffice Calc to graph time instead of the datapoint counts. Runs from 21:13-21:45 if you really want to know. Coolant and altitude on right axis, MPG and speed on left.
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Instant MPG varies wildly due to the hills, but if we zoom in on points 1100-1300 we can start to see we're getting ~25 MPG while climbing a slight hill, closer to 40 MPG when level. If we average the MPG over this entire section (simple average in the spreadsheet data) we get 34 MPG.
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So a stock Sienna, with several hundred pounds of extra weight (see below), at 45 MPH, on a average slight incline, is still getting on the order of 34 MPG. Vs a very low drag Tesla which managed an average of 24 MPG at the same speed.

When I finally get bored of this and speed up (I was on a freeway for this most level section of the trip), I still beat the Tesla in MPG despite going significantly faster.
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This very much proves my point that a DIY hybrid solution is going to have an extremely hard time beating out any modern hybrid on the market. Smaller engines are inherently less efficient than larger ones, and even more so because they are not optimized nearly as much as larger ones used in cars, because that takes lots of R&D, which is expensive, and small engines are almost always used in applications where high efficiency is not a priority, but cost is.

The 41% peak thermal efficiency of the engine used in the Sienna hybrid is nothing short of incredible. A typical coal fired power plant only has thermal efficiencies on the order of 35-45%. Most don't exceed 40% in actual operation due to startup/shutdown and not operating at peak efficiencies all the time, while a hybrid with reasonable driving could achieve an operating efficiency that almost equals it's peak efficiency, cause it can simply shut down when not needed, something a coal fired power plant can't really do. The electrical generation is also going to be very well optimized, though I don't have numbers for that. But thanks to the clever design of the HSD, the engine can directly power the wheels anytime it's running and bypass the conversion to and from electrical energy, putting energy from the engine straight to the wheels.

Below: The current status of my Sienna, as it was during the drive I captured the above data from.
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