How to convert a hybrid

Technical discussion on converting internal combustion to electric
T2
Groupie
Posts: 121
Joined: Sat, 08 May 2010, 04:51
Location: ON,CANADA

How to convert a hybrid

Post by T2 » Sat, 15 May 2010, 12:57

-coulomb Are you saying that these failures are common ?

No, I am not.

The several vehicles that I read about that were picked up 'as is' turned out not to be fixable. You probably know also that Toyota has been allowing 'secret' warranties in NA to avoid bad press.

With serviceable transaxles appearing on EBAY, apart from labour costs the problem has gone away. Since not many were trained on the Prius early on, this used to be a sensitive issue. For instance in late 2002 I was in the market and went to my local Lexus/Toyota dealership with questions. I didn't get very far, was told that both the Prius salesman and their Prius tech had taken lunch. That was all I wanted to know. They weren't taking this car seriously enough. I looked elsewhere.

This 415vac issue comes up frequently so I try to talk your language of 415Vac at 50Hz rather than 460Vac 60Hz we have here. In Canada there is a govt push towards our own 575Vac standard, created for no other reason than because we generate so much hydroelectric power which we sell down to the states - that our politicos thought we should establish our own standard. It confers no special benefit I might add and we try to ignore it. Most of our machinery exports go to the States so we have to install 575/460 Txfmrs all over our manufacturing plants so we can test them. Plus any machinery we buy from the US is going to be 460V, they are not about to let us wag the dog, our home market's too small. Electrical products designed specifically for the 575Vac standard have a price premium and provide limited choices. Thank god they decided against a 70Hz frequency change at the same time. Because if they coulda' , they woulda' !!

I am originally from the UK so my experiences of equipment going back 40 yrs must seem quaint by todays standard. Yep that one amp probably had a neutral feed to the control relays and contactors. Maybe repeated contactor coil inrush would stress the fuse. Of course it wouldn't be because of the extra relay ccts that got added on over the years, would it ? I hold up the offending component to the customer's electrician. And I get. " where did you get that from lad ? I've never seen one like that before."

For some reason I have always found my way to power electronics. When I was in the BBC we maintained 50Kw SW transmitters that were made by RCA in 1935. "The year 1935" I said "Tell me that is the model number and not the year" and they would tell me back "well we don't have any problem with that " Shortly after I left for a career in computers and later on thyristor motor drives. Commissioning newspaper press systems with connected drives sometimes totalling 1800Hp got me to Canada. If I haven't wasted too much of your time with all this, maybe it'll at least give me some street cred here. (BTW I think we have the 480v split phase - some offices use 277Vac area lighting) Let me just say I've read and concur with all your comments on control systems and move on.

Regarding converting a hybrid, the point I wanted to make is that that the option to turn a Prius into a BEV is a not a viable proposition even if the donor was free, the mech losses in the transaxle are not EV friendly.
Non running Honda Civic Hybrids are the real problem child. I see them playing out their end of life rotting at the back of consignment lots.
Who wants to convert a vehicle that looks like every other Civic on the road ?
The interesting one for me is the '99 Honda Insight. They are worth restoring anyway to original trim because of their unique styling.

As far as conversion to a BEV I think that they may not have the structural strength for a decent size battery pack - I could be wrong.

I have heard of Insights crossing over to the dark side and ending up being converted to street rods where the light weight really favours an engine upgrade. Obviously the manual version would be the candidate here.

Insights with bad CVTs and battery would be a choice for a series hybrid. Where to install the new traction motor still a question but a rewinding of the motorgenerator may not be necessary for a trial. Since 144Vdc originally powered the motor from 1000rpm then spinning it up to 4000rpm as a generator may produce 576Vdc. The engine is capable of 67Hp (50Kw) but at what rpm ? Needs to be researched and put up as a seperate thread. Anyone ?
T2

User avatar
coulomb
Site Admin
Posts: 3780
Joined: Thu, 22 Jan 2009, 20:32
Real Name: Mike Van Emmerik
Location: Brisbane
Contact:

How to convert a hybrid

Post by coulomb » Sat, 15 May 2010, 14:36

T2 wrote: This 415vac issue comes up frequently so I try to talk your language of 415Vac at 50Hz rather than 460Vac 60Hz we have here.
Ah, so that's split phase, with 230? and 115 coming off the supply transformer for lighting and office general purpose outlets?
In Canada there is a govt push towards our own 575Vac standard, created for no other reason than because we generate so much hydroelectric power ... that our politicos thought we should establish our own standard.
That's weird. I mean, countries have their own TV and power outlet standards because back before globalisation it was seen as a move to protect local industry. Indeed, we used to make our own valve (tube) B&W TVs (e.g. Pye), our own kitchen appliances (e.g. Mixmaster), and so on. I believe that even multinational companies like Philips did manufacture locally. Of course now the many differing standards is just a nuisance, and costs the world a lot of money because of all the specialisation that has to go on. So to introduce a new standard at this point in time makes no sense to me.
Yep that one amp probably had a neutral feed to the control relays and contactors.
Ah, the one amp fuse was for the control logic, not the 15 HP motor. Somehow I missed that point.
For some reason I have always found my way to power electronics. When I was in the BBC we maintained 50Kw SW transmitters that were made by RCA in 1935.
As a point of interest, and in brief, what were the issues with the old equipment?
If I haven't wasted too much of your time with all this, maybe it'll at least give me some street cred here.
Sure! Glad to have you here, with all that experience! Sorry about the baby talk in my earlier post; some misunderstandings led me to assume that you didn't have experience with power electrics. Your record speaks for itself.
(BTW I think we have the 480v split phase - some offices use 277Vac area lighting)
480/460, it's the same animal to me. We have the same thing here; our power which was always 240 V, and still is according to a multimeter poked into a wall socket, has been "redefined" as 230 V with a higher margin at the top end than at the bottom (e.g. 230 V +10% -5%). Perhaps you have the same issue in Canada, just multiplied by 2. Ok, now there's 277 V... is that three phase? Or just another single phase standard? Our 415 and 240 standard is staring to look very clean and tidy compared to North America, where I've heard of 110/115/120, 220/230/240, 208 (three phase? yay!), 460/480, 575, and now 277. No doubt there are others, and we must have an Australian standard above 415.

Interesting comments on the Insight.

Edit: clarified "multimeter in the wall".
Last edited by coulomb on Sat, 15 May 2010, 04:38, edited 1 time in total.
Nissan Leaf 2012 with new battery May 2019.
5650 W solar, 2xPIP-4048MS inverters, 16 kWh battery.
1.4 kW solar with 1.2 kW Latronics inverter and FIT.
160 W solar, 2.5 kWh 24 V battery for lights.
Patching PIP-4048/5048 inverter-chargers.

T2
Groupie
Posts: 121
Joined: Sat, 08 May 2010, 04:51
Location: ON,CANADA

How to convert a hybrid

Post by T2 » Sun, 16 May 2010, 14:47

coulomb - As a point of interest, and in brief, what were the issues with the old equipment?

When you join a supposedly prestigious organisation like the BBC you expect to be working with SOTA equipment and not feel like the curator of a radio museum ! The two RCA TXs were backup for the six 250Kw Marconi Senders that we had and were located in an adjacent hall. To walk through there was like being on a Boris Karloff movie set and with their Art Deco styling they seemed just the sort of apparatus you would be needing to bring a Frankenstein to life. There were no electrical issues although we had to do needless maintenance - for our benefit apparently, so that we kept familiar with their inner workings - but it was a big thing if one of them ever had to be powered up. Russian troops in Czechoslovakia sort of thing.
T2

User avatar
coulomb
Site Admin
Posts: 3780
Joined: Thu, 22 Jan 2009, 20:32
Real Name: Mike Van Emmerik
Location: Brisbane
Contact:

How to convert a hybrid

Post by coulomb » Sat, 24 Jul 2010, 16:30

Mr. Mik, back in December 2009 wrote: How about converting a NHW10 to fully electric by adding a third electric motor - replacing the ICE?


My original thought about that was "three motors? That's just silly". However, the thought that maybe it's not so silly has been rattling around in my mind over the last few days. For a while I've been saying to the common suggestion of "why not convert a Prius" (with the thought that it's half electric already, right?) that "actually, the Prius doesn't make a good pure EV good conversion". The main reason is that it doesn't have a conventional transmission, and the motors are not quite powerful enough to use as the main traction motor by themselves.



While this is true, it does of course have a transmission; it just happens to be made up of two electric motors and a fixed ratio planetary gear.



Some have argued that the Prius has a particularly inefficient transmission. Woody in this post came up with a figure of just over 80%:


Woody wrote:Estimates:

Small motor 90%

Large motor 95%

Inverters 97%



90% * 95% * 97% * 97% = 80.44%



Compare Manual transmission maybe 90%, Auto 80%, so not too bad.


However, the motor and inverter efficiencies are guesses and the two motors are not in series, so it's not valid to multiply their efficiencies. From this page:



Image



The "F" in this graph is temperature, in degrees Farenheit. It shows that at maximum engine speed, the losses are around 1300 W when hot (1550 W when cold). The combined maximum power from a NHW20 (2004) Prius is 82 kW, so that's 1.3/82 * 100% = 1.6% loss. 1.9% when cold. Some of that power comes from MG2, which is near the output of the transaxle, so it would have lower losses. If you take just the ICE power (57 kW per this Wikipedia article), the loss is 1.3/57*100 = 2.3%. I assume that the NHW10/11 transaxles are less efficient, but not worse than a factor of 2. So unless I've screwed up here, the transaxle is actually quite efficient, compared to the ~ 10% loss of a conventional manual transmission (and does that 10% figure even include the diff?).



So now I'm thinking that a Prius may not be such a bad donor after all, especially if you can get one cheap.



The hybrid system already provides reversing and regenerative braking, so a simple DC electric motor could replace the ICE. You would presumably use the same pack for the hybrid system as the traction motor, so that means a 200 to 300 V pack. This is a bit high for DC and a bit low for AC. I would consider using the open revolt controller with high voltage silicon, so say 350 A @ 288 V instead of 700 A @ 144 V. 350 A @ 156 VDC (output of controller) is some 55 kW electrical, which should provide similar power to the original ICE (43 to 57 kW, depending on the model). A monster DC motor would be overkill; an 8 or 9" DC motor would be plenty.



Of course, there is a big problem with this: the hybrid ECUs are probably rather intimately tied in to the ICE. However, it should not be too much harder than other conversions where the ECUs are kept... but I don't see many conversions where this is done. So there would be plenty of mucking about with faking of engine sensors and battery SOC to keep the various ECUs happy.



In summary, here are some of the advantages of converting a Prius to pure electric:

* Efficient transaxle with continuously variable ratio

* Regen provided and well integrated with the brake pedal

* Throttle sensor already provided

* 10-12 year old donors come up at low prices (NHW10s with dead hybrid packs). NHW11 and NHW20 models may be available cheap soon as well. Toyota vehicles of this age are of reasonable quality.

* The body has a low drag coefficient.

* You might be able to split the pack into two paralleled strings, such that one string might fit in the boot, and you could possibly drive the car home in hybrid mode by installing one string in the boot. You could take it along in the boot of the vehicle you drive to the vendor. This might be getting a bit fanciful; it would surely be a 2 hour job to transfer a lithium pack to a Prius, and only when you have done it a few times already.

* All Prius models have an LCD display already integrated, which could presumably be modified to display more EV-useful information. Older displays are typically in a sad state, so the original touch screen might need to be replaced with an ordinary LCD screen. There are plenty of buttons on the side that could be used for input if necessary.

* NHW20 models have electric air conditioning built in. Earlier models can presumably run from the traction motor, and the hybrid system will ensure that the motor runs when needed by the A/C system.

* There is room for some traction cells in the space vacated by the hybrid battery.

* You could limp home if the main controller or motor failed, using the transaxle motors only (like a petrol Prius that has run out of fuel).

* Most of the cells of the original hybrid battery could be sold to someone that needs refurbished cells for their hybrid Prius.



Disadvantages:

* There is presumably much work to fool the various ECUs that there still is an ICE there, and that there is a hybrid battery there that doesn't seem to deplete as fast as it is expecting.

* The Prius is a bit heavy, though I would think that the hybrid transaxle would not be much if any heavier than a manual transaxle.

* The 200-300 V pack voltage is uncommon, so controller choice is limited.



Undecided:

* I don't have a feel for how much room there would be for the battery pack. It's not the smallest of cars, so presumably it's no worse than a medium sized FWD car to find space for cells.

[ Edit: breaking -> braking ]
Last edited by coulomb on Sat, 14 Jul 2012, 18:52, edited 1 time in total.
Nissan Leaf 2012 with new battery May 2019.
5650 W solar, 2xPIP-4048MS inverters, 16 kWh battery.
1.4 kW solar with 1.2 kW Latronics inverter and FIT.
160 W solar, 2.5 kWh 24 V battery for lights.
Patching PIP-4048/5048 inverter-chargers.

Mr. Mik
Groupie
Posts: 66
Joined: Fri, 08 May 2009, 04:41
Location: Gold Coast, Aus

How to convert a hybrid

Post by Mr. Mik » Sat, 24 Jul 2010, 21:50

This page will give you some very interesting ideas:
http://99mpg.com/Projectcars/evinsight/

It shows a project to turn a Prius into an EV by welding the PSD to itself!

There is always a way if there is no other way!

User avatar
Simon
Senior Member
Posts: 431
Joined: Sun, 19 Aug 2007, 19:38
Real Name: Simon
Location: Perth WA
Contact:

How to convert a hybrid

Post by Simon » Sun, 25 Jul 2010, 00:24

I have often daydreamed about converting a Prius to pure EV. But kept thinking the same thing as Coulomb.
3 electric motors plus motor controller.. starts getting complex. And how do you stop it recharging the pack when you are using your 3rd electric motor? Will the car goto "ready" mode when it finds that someone's ripped the ICE out! etc, etc! Image
Autobeyours have a video up on Youtube of an all electric Prius. So it's not impossible for someone that knows what they are doing.

My plan was to put a series DC motor in place of the ICE and use it as a kind of turbo. It would be turned on for accelation only and rely on the stock emotors to cruise at 60-70kph.

Another advantage of the Prius as a donor is you get a fairly quiet vacuum pump, although it doesnt get to run very often with regen doing the majority of the braking.
And dont forget the 1000W continuous DC-DC converter.
    
Image
Last edited by Simon on Sat, 24 Jul 2010, 14:28, edited 1 time in total.

User avatar
coulomb
Site Admin
Posts: 3780
Joined: Thu, 22 Jan 2009, 20:32
Real Name: Mike Van Emmerik
Location: Brisbane
Contact:

How to convert a hybrid

Post by coulomb » Sun, 25 Jul 2010, 01:13

Simon wrote: And how do you stop it recharging the pack when you are using your 3rd electric motor?

I was about to say who cares, but you are right, this is "hybrid thinking" and will just waste pack energy by pumping it around a slightly lossy loop. I guess spoofing a high SOC almost all the time will help, but possibly not when you need it the most (when the real pack SOC is low). Plus, it might discourage regen when the main motor is off.

I guess it's another part of the "lying effectively to the hybrid system" problem.

I should check out the all-electric Prius, thanks for the pointer.
Nissan Leaf 2012 with new battery May 2019.
5650 W solar, 2xPIP-4048MS inverters, 16 kWh battery.
1.4 kW solar with 1.2 kW Latronics inverter and FIT.
160 W solar, 2.5 kWh 24 V battery for lights.
Patching PIP-4048/5048 inverter-chargers.

User avatar
Simon
Senior Member
Posts: 431
Joined: Sun, 19 Aug 2007, 19:38
Real Name: Simon
Location: Perth WA
Contact:

How to convert a hybrid

Post by Simon » Sun, 25 Jul 2010, 02:44

Oops double post.
Last edited by Simon on Sat, 24 Jul 2010, 16:48, edited 1 time in total.

User avatar
Simon
Senior Member
Posts: 431
Joined: Sun, 19 Aug 2007, 19:38
Real Name: Simon
Location: Perth WA
Contact:

How to convert a hybrid

Post by Simon » Sun, 25 Jul 2010, 02:46

Here is a direct link its a bit hard to find on their site All Electric Prius at Autobeyours

User avatar
Mesuge
Groupie
Posts: 168
Joined: Wed, 05 Mar 2008, 07:37
Contact:

How to convert a hybrid

Post by Mesuge » Sun, 25 Jul 2010, 15:18

Allow for a couple of points, firstly don't forget that apart from Prius (HSD) the system is also used/licensed in Lexus, Nissan, Ford hybrids. Moreover it comes in various power levels from 50kW - 120kw electrical. Perhaps 2mil of these cars has been produced up to this date, the surplus/salvage parts are relatively plentifull and cheap for the diy scene. So, far nobody managed to reuse the components in meanigfull way, which is rather shamefull. Perhaps it's because the motors are 650V, and the inverters are using booster circuit to prop up the 200-300V DC bus nominal voltage. Besides the Daimler-BMW-Chrysler alliance has bee producing very similar system to Toyota's HSD for years, but in much small quantities (few thousand cars per year), in any case these motors/inverters are there to stay too. Hacking the oem ECU for EV transplant nor welding the MG2-MG1 seem as viable strategy to go.

So, in the light of the non/available solutions on the market the only meanigfull approach remains to come up with a new controlling pcb board with opensource software, which will run the oem toyota inverter powerstage & MG2 motor combo, either in direct drive or attached to tranny, depending on required power output, prefered vehicle drivetrain setup etc. The tumanako project guys seem to be very close, although they focus on different power stage hardware at the moment, but in fact they declare to have universal, non-hardware specific system. This is the most likely way how to do it and perhaps get <120kW AC drivetrain bellow ~ $2k..
Last edited by Mesuge on Sun, 25 Jul 2010, 05:36, edited 1 time in total.
ImageCzech EV Club | blog, gallery, video | http://old.elektromobily.org

User avatar
coulomb
Site Admin
Posts: 3780
Joined: Thu, 22 Jan 2009, 20:32
Real Name: Mike Van Emmerik
Location: Brisbane
Contact:

How to convert a hybrid

Post by coulomb » Sun, 25 Jul 2010, 17:14

Simon wrote: Autobeyours have a video up on Youtube of an all electric Prius. So it's not impossible for someone that knows what they are doing.

Ah, I remember that conversion now. The Prius with the engine carcas with the hole in the block.

Alas, that vehicle didn't seem to get over 60 km/h in the video, and I didn't get the impression that it could do it. So while this was an interesting demonstration, I don't think it's a blueprint for future all-electric Prius conversions.
Nissan Leaf 2012 with new battery May 2019.
5650 W solar, 2xPIP-4048MS inverters, 16 kWh battery.
1.4 kW solar with 1.2 kW Latronics inverter and FIT.
160 W solar, 2.5 kWh 24 V battery for lights.
Patching PIP-4048/5048 inverter-chargers.

User avatar
coulomb
Site Admin
Posts: 3780
Joined: Thu, 22 Jan 2009, 20:32
Real Name: Mike Van Emmerik
Location: Brisbane
Contact:

How to convert a hybrid

Post by coulomb » Sun, 25 Jul 2010, 17:59

Mesuge wrote: Perhaps 2mil of these cars has been produced up to this date, the surplus/salvage parts are relatively plentiful and cheap for the DIY scene.
Well, yes, but probably 95% of those would be for the NHW20 Prius. Over time, the proportion of NHW30 Prius components would slowly increase.
So, far nobody managed to reuse the components in meaningful way, which is rather shameful.
I've never looked, but I'm not aware of a large source of such components. Perhaps I should look   Image
Perhaps it's because the motors are 650V, and the inverters are using booster circuit to prop up the 200-300V DC bus nominal voltage.
Huh? The 650 V is internal to the inverter; users don't have to deal with it directly.

Oh, perhaps you figure it's best to use standard induction or synchronous PM motors, and just reuse the cheap power electronics. Well, most ~400 V induction motors can be connected in star to become ~700 V machines, so they can presumably take the voltage. The bigger issue would be can they take the square waves from the inverter.
So, in the light of the non-available solutions on the market the only meanigful approach remains to come up with a new controlling pcb board with opensource software, which will run the oem toyota inverter powerstage & MG2 motor combo, either in direct drive or attached to tranny, depending on required power output, preferred vehicle drivetrain setup etc.
That's an interesting idea. You'd cut out some of the hassles of interfacing with the hybrid system, and replace it with interfacing to the inverter itself, which might be a whole lot easier, and you get full control. I like it.

Also, since you have full control, you could get the power stage to produce ~ 450 VRMS sine waves instead of ~ 650 VRMS square(ish) waves. Actually, I see that 650 V is for the NHW30, which would be rare and expensive at present; the NHW20 runs at 500 VDC. So that's some 350 VAC, a little low for standard 400 V industrial motors.
The tumanako project guys seem to be very close, although they focus on different power stage hardware at the moment, but in fact they declare to have universal, non-hardware specific system. This is the most likely way how to do it and perhaps get <120kW AC drivetrain bellow ~ $2k..
I don't see how you're going to get much more than 50 kW from an NHW20 MG2 (its design power). Presumably, they're already over-clocking it to the maximum to get that figure, and it's water cooled already, and it's amazing that they get such power from such a small motor as it is.

So I see a stock NHW20 MG2 as being useful for a very small car, or a medium sized car where high performance isn't important, or use a pair of them for a normal sized car. Using two motors and two inverters is insane if you are buying them off the shelf. But if you can get them cheaply, like under US$2k, then it's not so crazy at all. Especially when the motors and inverters are fairly compact.
Last edited by coulomb on Mon, 04 Jun 2012, 18:28, edited 1 time in total.
Nissan Leaf 2012 with new battery May 2019.
5650 W solar, 2xPIP-4048MS inverters, 16 kWh battery.
1.4 kW solar with 1.2 kW Latronics inverter and FIT.
160 W solar, 2.5 kWh 24 V battery for lights.
Patching PIP-4048/5048 inverter-chargers.

User avatar
Mesuge
Groupie
Posts: 168
Joined: Wed, 05 Mar 2008, 07:37
Contact:

How to convert a hybrid

Post by Mesuge » Mon, 26 Jul 2010, 01:08

Again, true the "iconic" gen2 Prius is the most common donor out there, and 50-60kW (gen2-gen3) doesn't seem as much apart from projects targeted mostly as city econoboxes. I think there is a project by some australian university to have prius MG2 in empty housing attached to gen1 miata's tranny. However, they are using semikron's powerstage so this is rehash of tumanako and they seem to be pretty behind them anyway..

Besides, the suggested approach of adding open source control board to toyota's powerstage & motor has the potential to be 2x cheaper than other available AC kits and to be based on quality oem components. Perhaps even some awd or independently powered front axle to get 2x 50kW would be possible with the Prius parts. Yes, twice the components and weight but still decent price for ~100kW system. Unless Tritium James or other high enders venture into sub 100kW territory based on cheaper ~50kW output powerstages this will remain vacant area for very long time. Not counting those various air cooled and low voltage golf buggy/forklift AC Curtis/Zapi kits, which are overpriced joke even before adding watercooling etc.

But there are other toyota/licensed hybrids (SUV) with 65-123kW AC perm motors as well, albeit not produced in such volumes, I think these are the 650V types. Their system is likely very same to Prius HSD only "supersized" to higher output..

The Prius powerstage module has been peaked into by various U.S. academic institutions and diyers alike years ago, the documentation is outhere. So, the basic functionality is known, the only thing left to decide now is to evaluate as to whether is it worth the extra dev work by running it from new open source control board. Or is it afterall just much easier to go the tumanako way - eat the price of semikron powerstage and get basically a bit cheaper Wavesculptor diy route, obviously with limited support, no compliance seals etc. If you add all the items this seems as perhaps only 1/3 cheaper than original Wavesculptor, so not much benefit in doing that. Hm, let's go back into reusing Prius powerstage deliberations..

Prius powerstage module overview:
http://www.techno-fandom.org/~hobbit/ca ... index.html
http://www.techno-fandom.org/~hobbit/ca ... ompon.html
http://www.eetindia.co.in/ART_880049914 ... a6d8c2.HTM

http://sourceforge.net/apps/mediawiki/t ... e=Inverter
http://sourceforge.net/apps/mediawiki/t ... e=STM32MCU
Last edited by Mesuge on Sun, 25 Jul 2010, 16:16, edited 1 time in total.
ImageCzech EV Club | blog, gallery, video | http://old.elektromobily.org

User avatar
coulomb
Site Admin
Posts: 3780
Joined: Thu, 22 Jan 2009, 20:32
Real Name: Mike Van Emmerik
Location: Brisbane
Contact:

How to convert a hybrid

Post by coulomb » Sun, 13 Nov 2011, 21:33

Recent events have triggered me to think about Prius conversions again.

It seems that having MG1 geared down (for torque) and MG2 not geared down (for speed) is a pretty ideal arrangement. So the temptation is to lock the ICE input shaft, rather than the often suggested idea of locking or welding the planetary gears so that they can't rotate (losing the benefit of the 2.6:1 reduction ratio on MG1).

However, I've been wondering, since MG1's RPM limit is 10,000 RPM, why does the Prius Hybrid computer limit MG1's speed to 6500 RPM when the ICE is not running?

It dawned on me that when the ICE is not running, the speed of the planetary gears is at its highest. The number of teeth on the sun/planet/ring gears is 30/23/78. When the ICE (connected to the planetary carrier) is not running, it seems to me that the planetary gears see 78R teeth per minute on one side (where R is the rotational speed of the ring gear, in revolutions per minute) and 30S teeth per minute on the inside (where S is the speed of the sun gear, connected to MG1). So each planetary gear will be spinning at (78R - 30S) / 23 revolutions per minute, relative to the stationary planetary carrier. When MG1 is running at 6500 RPM with the ICE stopped, the vehicle is doing 69 km/h (43 mph), and MG2 is doing some 2540 RPM. So the planetary gears would be doing (78.2540 - 30.(-6500)) / 23 ~= 17,100 RPM. If MG1 was allowed to spin at 10,000 RPM with the ICE stopped, that would be a vehicle speed of 104 km/h (65 mph), with MG2 at 3850 RPM, and the planetary gears would each be rotating at (78.3840 + 30.10000) / 23 ~= 26,100 RPM. Presumably, they would be in danger of flying apart, or overheating from friction, possibly burning the oil, or at least causing unacceptable losses in the transmission.

When the ICE and hence the planetary carrier is moving, although the planetary gears will still be whipping around at high speed, they won't be rotating so fast about their axes.

The final killer with my idea of leaving the ICE input shaft at zero speed is that the oil pump is apparently connected to the ICE input shaft. With the ICE shaft at zero RPM all the time, the oil pump would never be operating.

The possibility of locking the planetary gears is still viable, I suppose, but now the Prius becomes a direct drive vehicle without an oversized motor. The NHW10 models have a combined MG1/MG2 power of some 45 kW, which doesn't seem enough for direct drive.

So then the next best idea is to have a third electric motor to replace the ICE, with its own inverter. Then the Prius conversion is much like an ordinary conversion, just with a CVT in place of a manual or standard automatic transmission. The appeal of getting a donor vehicle very cheaply (in the case of NHW10 cars with worn out hybrid batteries) becomes diminished somewhat. Do I really want a 13 year old donor vehicle with the pack voltage set at around 288 VDC? I'm thinking no.

[ Edit: I've just found some notes that say that the 10,000 RPM limit for MG1 is only for the NHW20 model. Also, with the NHW20, MG1 power is 20 kW, so the combined total of MG1 and MG2 is a reasonable 50 + 20 = 70 kW, so running these models as pure electric using only the original motors and a welded planetary carrier may be viable. It would not be a high performance conversion, but probably acceptable. I suppose in a few more years, the earliest NHW20s will start to have hybrid battery failures, and some owners may choose to sell the car cheaply rather than replace the hybrid battery, at a cost of many thousands of dollars. ]
Last edited by coulomb on Sun, 13 Nov 2011, 10:48, edited 1 time in total.
Nissan Leaf 2012 with new battery May 2019.
5650 W solar, 2xPIP-4048MS inverters, 16 kWh battery.
1.4 kW solar with 1.2 kW Latronics inverter and FIT.
160 W solar, 2.5 kWh 24 V battery for lights.
Patching PIP-4048/5048 inverter-chargers.

Goombi
Senior Member
Posts: 532
Joined: Sun, 10 Aug 2008, 17:59
Real Name: Eugen
Location: Gympie

How to convert a hybrid

Post by Goombi » Mon, 14 Nov 2011, 17:22

HHHHHHi all,   In my topic about prius I have made a total assumtion about the feasability of prius conversion in 24 hours after i sat that time at the computor. I was all taken by the idea but the japs have not left us anything to work with other then confussion -many ideas- all too complex and unnecessary In conclussion I agree that the engineering and design of the gearbox is super excelent if not wastfull.If prius is to be resurected use it as what it was designed for a Hybrid. Regards to all

Had a bowel cancer and just finishe the Chemo it was a bit of a sh*tty experience.. but back to to normal and kicking.. Cheers

T2
Groupie
Posts: 121
Joined: Sat, 08 May 2010, 04:51
Location: ON,CANADA

How to convert a hybrid

Post by T2 » Sun, 03 Jun 2012, 14:31

@ Coulomb a couple of errors in your post.
First I think the planet gears should be 24 teeth.
The pitch circles of all the contacting gears should be tangential.

In which case if we are agreed the sun is 30t and the ring is 78t.
Then the sun plus twice the planet must equal the ring.
The only geometrical fit for this is when the planet is 24t.

http://www.d1ulookin4.com/PlanetaryAssembly/

Secondly when MG1 is 10,0000 rpm , any planet gear in the stationary carrier must be rotating at a more reasonable 30/24 of that i.e. about 12.5Krpm.

Thirdly the 10.4 : 1 ratio is exactly in the ballpark for a 400Hz induction motor. 400Herz.com are selling aircraft motors 100Vac which would be suitable with a 144Vdc battery.

The new problem is that Prius C retailing for USD19.5K have now arrived on the market. In case you're not aware these are using the original 1.5L engine in a 99HP package (down from 104Hp as if anybody cared).
Sure it's not a pure electric but it is a full hybrid with limited electric only operation as before. I have seen discussions where it may make more sense with a payback of three years to purchase one of these over a new Yaris for example.

This deserves mention since the resale value of conversions is not the best while the layout in cash is usually north of $10,000. The present is catching up to the future.

@Goombi, glad to hear you're good again.
It reminds that I am due for a checkup soon in that part of my abdomen. When they ask me How did it go ? I'll have my standard reply ready " I can assure you all that from now on my problems will remain behind me !" which doesn't tell them anything except perhaps - mind your own beeswax !!
T2

User avatar
coulomb
Site Admin
Posts: 3780
Joined: Thu, 22 Jan 2009, 20:32
Real Name: Mike Van Emmerik
Location: Brisbane
Contact:

How to convert a hybrid

Post by coulomb » Mon, 04 Jun 2012, 16:34

T2 wrote: @ Coulomb a couple of errors in your post.
First I think the planet gears should be 24 teeth.
The pitch circles of all the contacting gears should be tangential.

In which case if we are agreed the sun is 30t and the ring is 78t.
Then the sun plus twice the planet must equal the ring.
The only geometrical fit for this is when the planet is 24t.

Interesting. I agree with your reasoning, but these two sources say 23 teeth:

prius.ecrostech.com/original/Understanding/PowerSplitDevice.htm (Scroll down to "Gear Ratios" or search for "23")
http://priuschat.com/threads/for-those- ... nts.61121/ (This is for the 2010 model, but the other two numbers are the same, so by the maths this should be 24 teeth on the planet gears also.)

[ Edit: in the second link above, they actually discuss the discrepancy that you've pointed out. ]

You can also tediously count the teeth on this presumed (my me) to-scale (teeth count accurate) diagram:

http://eahart.com/prius/psd/
(Or just note that the top planet gear has a dot between teeth, and the bottom of that gear has a tooth, not a gap, so there are an odd number of teeth.)

I think that there are fewer teeth than mathematically correct so that there is a little more room for inaccurate positioning, and ease of inserting the gears. It means that the seating surface isn't exactly the middle of the teeth, or something like that.

I'll come back to the maximum planet gear rotational speed in a later post.

Edit: fixed screwed-up formatting
Last edited by coulomb on Mon, 04 Jun 2012, 06:42, edited 1 time in total.
Nissan Leaf 2012 with new battery May 2019.
5650 W solar, 2xPIP-4048MS inverters, 16 kWh battery.
1.4 kW solar with 1.2 kW Latronics inverter and FIT.
160 W solar, 2.5 kWh 24 V battery for lights.
Patching PIP-4048/5048 inverter-chargers.

User avatar
Simon
Senior Member
Posts: 431
Joined: Sun, 19 Aug 2007, 19:38
Real Name: Simon
Location: Perth WA
Contact:

How to convert a hybrid

Post by Simon » Mon, 04 Jun 2012, 18:36

http://www.youtube.com/watch?v=nHhl_GIX ... ztRLxulThY

Looks like this guy is using a home made controller using the Prius Power electronics.
http://www.diyelectriccar.com/forums/sh ... 52567.html
Last edited by Simon on Mon, 04 Jun 2012, 09:04, edited 1 time in total.

T2
Groupie
Posts: 121
Joined: Sat, 08 May 2010, 04:51
Location: ON,CANADA

How to convert a hybrid

Post by T2 » Wed, 06 Jun 2012, 09:53

I'll come back to the maximum planet gear rotational speed in a later post

@Coulomb Then I'll be all ears, as they say.

But seriously the difference with one less tooth on the planet gear is not going to be overwhelming to its rotational speed. Furthermore I'm sure you'll agree that this will not affect the gear ratio.

T2

T2
Groupie
Posts: 121
Joined: Sat, 08 May 2010, 04:51
Location: ON,CANADA

How to convert a hybrid

Post by T2 » Sun, 10 Jun 2012, 16:41

PART ONE

How to convert a hybrid :
From what I have learned over the years I would recommend as best practice for an electric transmission to be a 10krpm motor working into a 10:1 gearbox to provide 100Km/hr. I would add the proviso that the motor V/Hz must not be compromised below around 6600 rpm. And the icing on the cake would be the ability to operate at up to 300% nominal current below this particular rpm without exceeding the battery 4C rate since what is termed a "good launch" is key to establishing useful acceleration benchmarks.

Although I have rejected the idea of a Prius electric-only conversion in the past it was mainly because the electronic interface is not too constructor friendly, voltagewise that is. The mechanical interface is also problematic in having too many intermediary spindles transferring power between the HSD axis and the front wheel axis. Possibly 6% torque loss per interchange when under load.

Then something happened with the arrival of Coulomb's post six months ago here causing me to reconsider. I realized that a donor Prius may in fact bring something to the table after all providing the constructor is prepared to discard the two motors, MG1 and MG2, together with their associated electronics package. A technology you cannot master is a liability not an advantage. Taking that step made the outlook seem brighter. His post contained this :

- Coulomb Posted: 2011 November 14 at 1:33am
It seems that having MG1 geared down (for torque) and MG2 not geared down (for speed) is a pretty ideal arrangement. So the temptation is to lock the ICE input shaft, rather than the often suggested idea of locking or welding the planetary gears so that they can't rotate (losing the benefit of the 2.6:1 reduction ratio on MG1).

Let's combine ideas here and see where it goes.

In essence the engine and then MG1 need to be removed first up.
Next, the planet carrier/gear cage has to be mechanically restrained somehow so that it is prevented from rotating relative to the chassis.
An induction motor as specified should then be mated into the sun gear of the HSD planetary in place of MG1. Thus displacing a fragile technology of demagnetisable magnets with uncertain temperature constraints and little safe margin for overcurrent with a technology that is more understood, more able to withstand abuse and less susceptible to temperature extremes.

For the mechanical side, the HSD planetary offers a reduction ratio between the 30t sun gear and 78t ring gear of 2.6 : 1.
The ring gear of the HSD couples to the front wheel axle through those aforementioned spindles to the final differential with a cumulative ratio of 4.11 (PRIUS MY2004-9) Combined with the HSD planetary ratio this gives an overall ratio of 10.7 : 1 which is in the ballpark for a non compromised design.

Doubt was raised on the planet gears rotational speeds since at 100km/hr the induction motor will be rotating at around 10Krpm, the 30t sun gear causing the four 24t planet gears in the stationary carrier to rotate around 12.5Krpm. Faster speeds may be possible depending on the durability of the planet gears.

Regarding lubrication, a suggestion was made years ago on the Yahoo Group, Prius_Technical_Stuff to reduce gearing losses   by replacing the OEM transmission oil with Mobil ONE in the transaxle. Possibly this low viscosity oil will reach the HSD as well or some provision might be made.

T-J's WaveSculptor drive has auditioned a high efficiency 1E2 100Vac 50Hz induction motor from Sew Eurodrive. This has the copper rotor cage but it is not the highest effcy out there at the present time, Premium efficiency 1E3 motors are now available. Not only that but its Volts per Herz value of 2.0V/Hz will force the use of least a 360Vdc rail voltage for the inverter.

Consequently this motor with a V/Hz of 2.0 would be unsuitable for the Prius' MG1 replacement, as this value is six times larger than optimal, that's assuming that 120Vdc operation is desired.

As a matter of fact even the use of a 360Vdc supply would still only place base speed at around 3300 rpm which for the Prius transaxle corresponds to a speed of approximately 20mph. For anyone who knows anything, base speed occurring at 20mph is rather low and of course a compromised power/speed envelope is something one tries to avoid. Plus the lower speeds will require compensating with machines of greater torque thus requiring the constructor to pony up for a 7.5Kw machine or even an 11Kw when it can be shown that a 3.5Kw frame size would have been equally capable when used in the right setting. At the present time I think I am right in saying that no fractional V/Hz machines have run on the W-S.

Now there would be some who would say that this is an elitist approach to be expecting customers to install high voltage power supplies and supersized motors. However with my usual good breeding I shall just let the subject alone.

Part two will follow later.
T2

User avatar
coulomb
Site Admin
Posts: 3780
Joined: Thu, 22 Jan 2009, 20:32
Real Name: Mike Van Emmerik
Location: Brisbane
Contact:

How to convert a hybrid

Post by coulomb » Mon, 11 Jun 2012, 05:02

T2 wrote: I would add the proviso that the motor V/Hz must not be compromised below around 6600 rpm.
It seems to me you want to have constant torque up to 6600 rpm, and almost constant power after that. That seems a bit of a high goal to me, as I hope I can show below.
... Consequently this motor with a V/Hz of 2.0 would be unsuitable for the Prius' MG1 replacement, as this value is six times larger than optimal, that's assuming that 120Vdc operation is desired.
I think that there must be an error in your maths there.
As a matter of fact even the use of a 360Vdc supply would still only place base speed at around 3300 rpm
Base speed is where you run out of volts to maintain the standard V/Hz ratio, right? So if you have 360 VDC, that's around 250 VAC (divide by 1.414). I'm ignoring battery sag here for the sake of simplicity. With 2 V/Hz (100 VAC for 50 Hz), that's 250 / 2 = 125 Hz, or 125 x 60 = 7500 rpm, possibly more than the SEW motor can handle.
which for the Prius transaxle corresponds to a speed of approximately 20mph. For anyone who knows anything, base speed occurring at 20mph is rather low and of course a compromised power/speed envelope is something one tries to avoid.
I don't agree with that. I think that provided a motor provides approximately constant power after base speed, within limits, the lower the base speed the better.

The quickest way to 100 km/h will be the way that provides the highest average torque; torque provides force to the vehicle, and simplifying a lottle. this provides acceleration. Let's consider two examples; same vehicle, same top speed, same transmission ratio, same power motor. One has a high base speed, say 6600 rpm, the other a low base speed, say 2000 rpm. For simplicity, let's assume that power above base speed is constant. I know that this isn't exactly the case, but I believe it will illustrate the point.

The second vehicle's motor is producing 3.3x the torque at base speed (and from zero up to that speed), because torque is power divided by speed. So although the first motor doesn't lose torque until 6600 rpm, the torque that it has is 3.3x less than the second vehicle's motor.

So really, you want a motor with higher V/Hz, which sounds bad, so you run out of volts earlier, which sounds worse, so the torque drops off earlier, which definitely sounds bad. But the size of the motor is proportional to its power, and the lower the base speed, the higher the torque you get to the wheels.

Another way to look at it is this: acceleration is what we want. This comes from torque at the wheels. With a fixed ratio transmission, this means we want the highest average torque from the motor. That corresponds to the highest area under the torque speed curve, which corresponds to the highest average height on the power speed curve, since power is the integral of torque with speed. By putting the base speed higher, you end up with a longer triangular ramp of power, where the average is half the height of the triangle. From base speed to the end, the power is the same, maximum all the way. So to maximise the acceleration, you have to minimise the triangular area, which means making the base speed as low as possible. In practice, of course, you can't keep the power near constant over a very wide range, so there is a limit to how low the base speed can go. But something like 2000 rpm will give a better result than something like 6600 rpm, for typical motors.
Last edited by coulomb on Sun, 10 Jun 2012, 19:13, edited 1 time in total.
Nissan Leaf 2012 with new battery May 2019.
5650 W solar, 2xPIP-4048MS inverters, 16 kWh battery.
1.4 kW solar with 1.2 kW Latronics inverter and FIT.
160 W solar, 2.5 kWh 24 V battery for lights.
Patching PIP-4048/5048 inverter-chargers.

User avatar
coulomb
Site Admin
Posts: 3780
Joined: Thu, 22 Jan 2009, 20:32
Real Name: Mike Van Emmerik
Location: Brisbane
Contact:

How to convert a hybrid

Post by coulomb » Mon, 11 Jun 2012, 05:11

A final example: if base speed is at 6600 rpm and 66 km/h, then at 33 km/h the motor will be putting out half of its peak power (peak power occurs at base speed). For a vehicle with everything else the same but base speed at 20 km/h, at 33 km/h it will already have been at peak power, and still be at near peak power.

At 33 km/hr, when the base speed is at 66 km/h, the batteries won't be providing peak power yet.

T2 mentioned being able to run at 300% of nominal current at low speeds; I don't think it's practical to get a controller to do this. A controller has a particular current limit, and that sets the maximum torque. If it could do 300% of that current at low speeds, it could do 300% at higher speeds as well (if the battery could provide the power), so that 300% would really be 100% of its actual maximum current. You can't get current for free; you need the IGBT grunt to back it up, and all the cooling etc that goes with that.
Nissan Leaf 2012 with new battery May 2019.
5650 W solar, 2xPIP-4048MS inverters, 16 kWh battery.
1.4 kW solar with 1.2 kW Latronics inverter and FIT.
160 W solar, 2.5 kWh 24 V battery for lights.
Patching PIP-4048/5048 inverter-chargers.

User avatar
coulomb
Site Admin
Posts: 3780
Joined: Thu, 22 Jan 2009, 20:32
Real Name: Mike Van Emmerik
Location: Brisbane
Contact:

How to convert a hybrid

Post by coulomb » Mon, 11 Jun 2012, 15:04

coulomb wrote: Base speed is where you run out of volts to maintain the standard V/Hz ratio, right? So if you have 360 VDC, that's around 250 VAC (divide by 1.414). I'm ignoring battery sag here for the sake of simplicity. With 2 V/Hz (100 VAC for 50 Hz), that's 250 / 2 = 125 Hz, or 125 x 60 = 7500 rpm, possibly more than the SEW motor can handle.

Well, there's something I'm doing completely wrong here. I've just looked at the actual torque speed curve for 380 V, and it's less than 3000 rpm:

Image

Perhaps my assumption that slip remains negligible at high loads is wrong.

Anyone spot my error?
Nissan Leaf 2012 with new battery May 2019.
5650 W solar, 2xPIP-4048MS inverters, 16 kWh battery.
1.4 kW solar with 1.2 kW Latronics inverter and FIT.
160 W solar, 2.5 kWh 24 V battery for lights.
Patching PIP-4048/5048 inverter-chargers.

User avatar
coulomb
Site Admin
Posts: 3780
Joined: Thu, 22 Jan 2009, 20:32
Real Name: Mike Van Emmerik
Location: Brisbane
Contact:

How to convert a hybrid

Post by coulomb » Mon, 11 Jun 2012, 15:52

Sorry for hijacking your part of the thread, T2, but I just wanted to post a curve for an IPM motor that was being called a "hybrid" motor:

Image

This motor runs on a 360 Vdc bus, spins up to 11 000 rpm, and only has about 12% peak power drop from 3500 to 11 000 rpm.

I suspect that the amount of power drop in an induction motor depends on the size of the air gap. With a smaller air gap, as in the Tesla Roadster's motor, they seem to get a smaller power droop than the approximately 1/f droop exhibited by the SEW motor above.

Image
That seems to be about a 45% drop in power, over a 2.7x speed range. If the power drooped by 1/f, this would droop to more like 37% of peak power, so it's doing about 22% better than 1/f. The IPM motor is doing about 275% better than 1/f.

You can see why manufacturers prefer the IPM motors, with their wide speed range with almost constant power.

Edit: I meant to say that both of these graphs have been posted before, but I don't think I did a side by side comparison like this.
Last edited by coulomb on Mon, 11 Jun 2012, 05:54, edited 1 time in total.
Nissan Leaf 2012 with new battery May 2019.
5650 W solar, 2xPIP-4048MS inverters, 16 kWh battery.
1.4 kW solar with 1.2 kW Latronics inverter and FIT.
160 W solar, 2.5 kWh 24 V battery for lights.
Patching PIP-4048/5048 inverter-chargers.

User avatar
coulomb
Site Admin
Posts: 3780
Joined: Thu, 22 Jan 2009, 20:32
Real Name: Mike Van Emmerik
Location: Brisbane
Contact:

How to convert a hybrid

Post by coulomb » Mon, 11 Jun 2012, 17:10

coulomb wrote: Anyone spot my error?

Weber pointed out one glaring error: I've been forgetting that this is a 4-pole motor, so at 50 Hz, synchronous speed is 1500 rpm, not 3000 rpm. But that doesn't explain all the difference; considering only the V/f ratio, the base speed would be just under 4000 rpm (265/100 x 1500 rpm minus slip speed).

I think I've been ignoring two effects; one I suggested above is that slip becomes significant at that load, but not that much. The other thing is that to get that sort of torque from the motor, the controller is increasing the field current over nominal. This has two effects; one is greater torque, the other is a higher back-EMF for the same speed. So for high torque, the controller needs higher voltage for three reasons:
1) More field current requires more voltage out-of-phase with the stator current. This will increase the length of one of the legs of the vector diagram, which will increase the vector sum (which represents total voltage to the motor).
2) More field current causes more back EMF for the same speed, so the controller needs to increase the in-phase voltage to overcome the back EMF. (That increases the length of the other leg of the vector diagram.)
3) More torque requires more in-phase current, which requires a little more voltage to force the current to flow against the winding impedance.

These three effects are in addition to the need to increase the volts to maintain the V/f ratio when the speed of the motor is increased. So these combine to reduce the base speed from some 3900 rpm to 2700 rpm.

Actually, the V/f ratio is probably a bit crude when applied to a proper motor controller. The voltage will have to go up about linearly with speed to overcome the inductance of the windings and the greater back-EMF, but this will come about automatically as the controller adjusts its vectors to achieve the desired speed and torque. It's a convenient motor parameter, along with nominal speed and power, but I suspect it doesn't get used directly in controller operation.
Nissan Leaf 2012 with new battery May 2019.
5650 W solar, 2xPIP-4048MS inverters, 16 kWh battery.
1.4 kW solar with 1.2 kW Latronics inverter and FIT.
160 W solar, 2.5 kWh 24 V battery for lights.
Patching PIP-4048/5048 inverter-chargers.

Post Reply