How to convert a hybrid

Technical discussion on converting internal combustion to electric
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coulomb
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How to convert a hybrid

Post by coulomb » Sat, 19 Dec 2009, 18:52

This topic is prompted by two posts on the Ebay finds thread. The context is that a 1998 Prius has come up on Ebay cheap, because its high voltage traction pack as died and the car won't start. It's becoming a common story: the owner gets some expensive quotes for a replacement pack, and decides to sell cheap to cut his/her losses.
acmotor wrote: I'd just re-instate/replace/upgrade the battery pack and use or re-sell.
Honestly, the prius emotor (even the genII) is almost not worth considering as EV only. The stated peak kW is rather optimistic and the achievable continuous kW must be down around 10kW or less. This in a 1,500kg or so EV (more if you ad more batts) is not very useful.
Keep in mind that the electromechanical nightmare was tuned for hybrid operation.

If you were thinking a conversion, then ICE out... new motor/controller/battery pack would be all you would need ! Image
antiscab wrote: yeh, by conversion i definately meant ditch all the ICE bits.

keeping the e-motor could be good for regen though :p
It seems to me that when something like this comes up, there are three reasonable possibilities:

* Repair the battery, and leave the car as a standard HV (Hybrid Vehicle) (some might say Hybrid Electric Vehicle, but it's really not electric)
* Replace the HV pack (usually really small, less than 1 kWh useable) with a new Lithium or Lead Acid pack, of at least 5 kWh capacity, making it a Plug-in Hybrid Electric Verhicle (PHEV)
* Replace the ICE and HV pack with a large Lithium or other pack, usually at least 15 kWh capacity, making it a full Electric Vehicle (EV). Either the existing hybrid motors could be retained, or also replaced.

Acmotor and antiscab seem to be implying that the Prius motors (especially on the pre-2004 models) are too weak for effective EV or even PHEV operation. I disagree that it's too weak for PHEV operation; the Prius is a fine hybrid, and making it plug-in hybrid in my opinion makes it better. This despite that fact that it likely can't do much electric-only driving: fine, drive it as a hybrid that uses half (depending on distance travelled) the petrol of a HV. It's like a range extended EV where you have to make partial use of the range extender all the way through a drive, not just at the end and only if needed.

As for a Prius as an EV, I think it could be done. The NHW20 model (2004-2009, the most popular model) has a 50 kW MG2 and a smaller MG1. It seems that MG1 is capable of generating some 30 kW, per Section 5.3 of this report (4MB). If these could be combined sensibly, making use of the higher speed range of MG1 (10,000 RPM), this would make a decent EV. From the same report, MG2's continuous power is some 21 kW at 35°C coolant temperature.

However, the Prius is but one example of a hybrid vehicle (though certainly the most common one to date).

What do forum participants think of the various ways that a hybrid vehicle could be converted to "more electric"?
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How to convert a hybrid

Post by Squiggles » Sat, 19 Dec 2009, 23:21

You would not start with a toymota, the arrangement is an electromechanical nightmare. I think it may have been designed by a team of first year undergraduate mechatronic students in Japan, sponsored by Exxon or Shell!

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Post by coulomb » Sat, 19 Dec 2009, 23:54

Sorry, I can't agree. I think it's very well engineered. But we've disagreed on this before.

However, I'll agree that the final reduction of just over 4.1:1 with two lay shafts seems totally ridiculous:

Image

Power goes from the 36 toothed wheel to the 75 toothed. Why not just put 148 teeth on the final gear and have no lay shafts or chains?

At least in the 2010 model they have gotten rid of the chain.

Edit: the ratio is 4.1, not 4.0, so 148 teeth would do it, not 144.
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How to convert a hybrid

Post by acmotor » Sun, 20 Dec 2009, 00:18

The electromechanical mastery of a VHS mechanism comes to mind.
There was no question the mechanism was a marvel of design and consumer engineering. The machining tollerances, precision bearings etc.

Thankfully DVD came along. Image

Sorry, I see a lot of parallels with the prius and VHS.
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How to convert a hybrid

Post by Squiggles » Sun, 20 Dec 2009, 15:41

AC, that's brilliant, this system was not designed by first year undergraduates...it was done by engineers made redundant at Sony when they stopped designing VHS recorders....just had to scale it up a bit.

That said just the whole business of 2 electric motors and one ICE added to a ridiculously complex transmission all to get the equivalent economy of a good diesel with half the performance has to be someone's little joke on the world!

Just love that chain driven piece with a ratio of 0.97:1 Image

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How to convert a hybrid

Post by Squiggles » Sun, 20 Dec 2009, 15:49

coulomb wrote: Power goes from the 36 toothed wheel to the 75 toothed. Why not just put 148 teeth on the final gear and have no lay shafts or chains?


Not my field of expertise, but I do recall that it is as much to do with diameter as with number of teeth...so a 144 tooth gear would be big. They could have gone 26/107. Would have been a damned sight more efficient as well!

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Post by coulomb » Sun, 20 Dec 2009, 17:41

Squiggles wrote: That said just the whole business of 2 electric motors and one ICE added to a ridiculously complex transmission all to get the equivalent economy of a good diesel ...

You have to be careful comparing the fuel economy of diesel engines verses petrol engines.

Diesel has 20% more energy per litre, so it's not hard to get better economy (on a per litre basis) starting with a 20% more energetic fuel.

Diesel emits 14.7% more CO2 per litre than petrol. But I see from another thread that you are a climate change skeptic, so I guess you don't care about that.

Generally (though it varies from time to time and place to place and on the relative demands of the two fuels) diesel costs more per litre than petrol, by (for the sake of this argument) very approximately 10%.

So there is more energy, carbon, and money in a litre of diesel than a litre of petrol. So if a turbo diesel engine consumes about the same litres of diesel per 100 km than a Prius engine consumes petrol per 100 km, then you are still 15% better off for CO2 emissions with the Prius, and still better off by roughly 10% with the Prius on the basis of the out-of-pocket cost of fuel. Plus, the diesel engine will be emitting 20% more waste heat than the Prius engine. But again as a climate change skeptic, you probably don't care about that either.
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How to convert a hybrid

Post by Squiggles » Sun, 20 Dec 2009, 20:03

Diesel is cheaper than petrol where I buy it. It also takes less energy to produce than more highly refined petrol so you better factor that into your calculations as well :). It is actually cheaper to produce than petrol and is only as expensive as it is due to the taxing structure and the greed of the producers.

There are some article out there that suggest that diesel and petrol produce approximately the same level of CO2 ( http://www.ecotravel.org.uk/fuels_5.html ). At the same time producing less CO and more NOX. It is all very complicated!! Then add to that the new series of higher efficiency petrol cars that are actually getting as good or better fuel economy as many hybrids.

Personally I see hybrids as a waste of time and basically are just publicity tools. If we are serious about reducing pollution then city dwellers should drive EVs or use public transport, for the occasional long drive requirement they could hire an ICE car.

edit: Burning coal has to be the biggest problem for us! All the while governments allow more and more mines to open and coal production continues to increase.....I am sure tax revenue has nothing to do with it!!
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Post by acmotor » Sun, 20 Dec 2009, 21:10

You have to ask the question... with all Toyota's prius experience, why aren't the selling an EV, right here and now ? Or for the last 10 years for that matter.
I think we all know the answer and its not technical.

Now back to converting a hybrid. Image
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Post by woody » Mon, 21 Dec 2009, 02:52

This is probably the place to bring up the top gear experiment where they flogged a prius around their track and had an M3 following it, keeping pace. The M3 used less fuel.

I have been in a prius a few times (NZ Taxis) in the last month. As a passenger I got a bit car sick watching the display, and it sounds like the prius has very poor clutch control :-). I'm looking forward to driving one.

The owner/driver said there were a few high mileage gen Is around NZ with ~250k on the clock, still going strong with just brake, oil and tyre changes. His gen2 had 80k on it.

I wonder if I can try a blade Getz over there...
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How to convert a hybrid

Post by Squiggles » Mon, 21 Dec 2009, 02:58

Although I do enjoy watching Top Gear I don't have much faith in their tests. I think the show would lose some funding if they suddenly found non hydrocarbon fuelled cars to be inferior.

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Post by Mr. Mik » Mon, 21 Dec 2009, 12:31

How about adding some plug-in-charging to drive down further the fuel consumption of hybrid?

This might be possible by adding more battery capacity.
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Post by coulomb » Mon, 21 Dec 2009, 15:06

Mr. Mik wrote: How about adding some plug-in-charging to drive down further the fuel consumption of hybrid?

Yes, that was my second option; make it a PHEV. I suppose the existing HV battery could be left in place or replaced altogether, depending on its condition and the availability of spare cells or modules.

This option would be more palatable in the Prius if it could do higher speed EV-only driving. There are some mods that can be purchased (none that are free that you could implement yourself that I know of) which raise the maximum pure-EV speed to 80 km/h and even 110 km/h.

Then, it becomes an EV with a permanent range extender. For short trips, it becomes almost a pure EV, just with slightly worse performance as it has to drag around an extra ~80 kg (total guess) of ICE.
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Post by coulomb » Mon, 21 Dec 2009, 15:17

Squiggles wrote: They could have gone 26/107. Would have been a damned sight more efficient as well!

Indeed; from http://www.treehugger.com/files/2009/03 ... -specs.php, talking about the 2010 model compared to the 2004 model:

* The transaxle is lighter in weight and reduces torque losses by as much as 20 percent compared to the previous model.
...
* Taken together, the inverter, motor and transaxle are smaller and 20 percent lighter.

The latter is impressive, considering that the engine went from 1.5 to 1.8 litres! (that's 2 to 2.4 bottles of boose Image )

I wonder if manufacturers do this deliberately: version 1 of something innovative (in this the NHW20, the 2004 and third model) is delivered with something crippling performance, so maybe the competition doesn't work so hard to do better. Then in version 2 (here the NHW30 or 2010 model) they undo the crippling and are able to offer increased performance.

Edit: splling and context
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Post by acmotor » Mon, 21 Dec 2009, 16:34

coulomb wrote:
* The transaxle is lighter in weight and reduces torque losses by as much as 20 percent compared to the previous model.


Seriously guys, if it was possible to reduce the transaxle loss by 20%, what was it before and what actually is it now ? (personally I doubt this number).
What it probably assures us is that the whole drive system whilst an 'engineering masterpiece' is a waste of energy.

I do feel that Toyota engineers are learning on the run. (well probably quite normal engineering actually on things new).
They are still being held back by trying to build a hybrid. Remember that several manufacturers, Mitsubishi included, have said that they will never build a hybrid and are building BEVs.

On the prius battery pack question. It is not that easy to go from 80kmph to 110kph in top speed as you well know if you simply don't have the kW available.
The existing NiNH pack has a specific power of 21kW peak and by the time this has made its way through to the wheels there is maybe 15kW left (for a few minutes). That simply won't push a 1500kg prius at 110kmph at anything other than down hill.

Add some extra battery pack and you only prolong the agony. Good for sub 60kmph around town and that is viable EV territory anyway.
Hey a prius will do 100,000,000,000 miles per gallon for the first 50km if you add a reasonable battery pack and run EV only mode. Then probably 20mpg for the next 50km as it drags the extra battery pack around ! (sorry about the mix of units, I think you get the point though)

Granted, a genIII could be more viable but we'll have to wait for some years for the secondhand market to catch up before the experimenters buy in ?

IMHO, it was a real negative for toyota to have increased the ICE size in genIII.
This was a real admission that the product was falling short. It was a simple (lazy ?) fix to up the ICE !
The improvements should have come via the EV path.
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Post by bga » Mon, 21 Dec 2009, 19:27

We shouldn't be too harsh on the Prius; It's a good design for its intended market.

I think that Toyota has been very clever in minimising the heavy and expensive battery while delivering some useful value from it. But, as we see, the design isn't very friendly for anything but it's hybrid role.

One real problem for the whole petrol hybrid concept is that despite all the added complexity, it's still not as economical as a small turbocharged diesel sedan.
The Ford 'eco' (more green paint?) Fiesta claims 3.7l/100km.

Would I be correct in assuming that the engine size has a lot to do with the single consumer metric - kW. (which is a bit like Mpix in cameras - more is not necessarily better)
Or, maybe the Prius is now like all the other car models: minnows evolving into whales.
It's odd that for the last 20 years, the succesive bigger, better, more economical and powerful editions of the models actually haven't become any more fuel efficient than they were in 1990.

All the component efficiency and weight improvements help, but the big baddie - GVM - is apparently completely off the radar.

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Post by Johny » Mon, 21 Dec 2009, 19:42

bga wrote:....
All the component efficiency and weight improvements help, but the big baddie - GVM - is apparently completely off the radar.
That's the conclusion (broadly) I have drawn. If you don't do anything extreme with drag or rolling resistance (and stay with the common vehicle look) then weight tends to dictate fuel economy regardless of engine size.

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Post by Electrocycle » Mon, 21 Dec 2009, 21:50

cars are much safer, more comfortable, and often have much better performance than they used to.
All of those things have eaten up the improved efficiency (more weight, size, and power)
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Post by juk » Tue, 22 Dec 2009, 02:50

acmotor wrote:
coulomb wrote:
* The transaxle is lighter in weight and reduces torque losses by as much as 20 percent compared to the previous model.


Seriously guys, if it was possible to reduce the transaxle loss by 20%, what was it before and what actually is it now ? (personally I doubt this number).


What's 20% of 10% losses? That's right it's 2%. But it sounds much more impressive if you say you reduced something by 20% than by 2%. Unless you take the viewpoint you have, but that would be a minority.

That said, i have no idea what they were before and what they are now, though i'm convinced the above logic is the reason why you can reduce a number that should be less than 20% by 20%.

edit:
I'm going to have to use that. When i operated the wiluna gold mine, we increased recovery by about 6%, but now i can say we reduced the losses by almost 50%.
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Post by Mr. Mik » Tue, 22 Dec 2009, 02:54

How about converting a NHW10 to fully electric by adding a third electric motor - replacing the ICE?

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Post by Electrocycle » Tue, 22 Dec 2009, 04:09

it'd be an interesting way to do it, and probably not super hard. The ECU is already giving an output to the throttle, and you could put the ICE sensor setup on the electric motor to keep it happy.

You could essentially have the car's original control system requesting extra electric power instead of ICE power.
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Post by acmotor » Tue, 22 Dec 2009, 04:15

Mmmmm, and the 3rd emotor could drive the generator and charge the battery pack too ! Image

I think you would soon be chopping it all out and going for one big emotor. Image
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Post by woody » Tue, 22 Dec 2009, 04:23

Mr. Mik wrote: How about converting a NHW10 to fully electric by adding a third electric motor - replacing the ICE?
You could just treat the two existing motors as a particularly lossy CVT transmission.

You'd want to turn off the "Regenerate the batteries from the motor" function.

The prius is heavy. 1250 for a Gen. 1, 1400 for 2 or 3.
Drag is good 0.29, 0.26, 0.25 for Gen. 1,2,3 - but how much highway driving are you going to do?
You've still got to add batteries - so more weight.

For comparison, a VR Commodore is about 1375kg, 40-55cm longer, 5-10cm wider, 4 cm lower.

A Mk I Cortina is same length as a Gen 1, 10cm narrower, 16cm lower but only 800kg.

I still say fix it and flog it off to buy something fun.
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Post by coulomb » Tue, 22 Dec 2009, 06:09

woody wrote: You could just treat the two existing motors as a particularly lossy CVT transmission.

Would it be all that lossy in comparison? With 90%+ inverters and 90%+ motors, verses a (guessing) 80% transmission?
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Post by coulomb » Tue, 22 Dec 2009, 06:15

bga wrote: One real problem for the whole petrol hybrid concept is that despite all the added complexity, it's still not as economical as a small turbocharged diesel sedan.
The Ford 'eco' (more green paint?) Fiesta claims 3.7l/100km.

I read about that in the latest "Road Ahead" from the RACQ. Impressive numbers, though not as good as a Gen 3 Prius at Carbon Dioxide emissions (diesel has about 15% more carbon per litre than petrol). But the other thing is that it's a new model not available yet.

Perhaps you should compare it with the recently released (but still unobtanium by mortals) PHEV Prius. Compare vapour with vapour Image !
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