# High performance hybrid?



## terra (Mar 8, 2010)

Hey guys,
Looking for input on a possible hybrid I'm doing. I've got a brand new BMW 5 series chassis, and a brand new M3 V8 engine. I'm looking for ways to improve cruising fuel economy without losing the performance aspect. I'll be shedding some weight by losing some of the interior electronics, all new carbon fiber body panels, and a smaller engine than the M5 V10. I'm not trying to spend another $25,000 having a company design an entire hybrid system for it, so what can I do on a smaller scale? Something to power the vehicle in low speed city settings, then switching to ICE for spirited driving with the electric motor combining for maximum needs.

Suggestions?


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## toddshotrods (Feb 10, 2009)

I have been toying with this idea for almost two years now for my daily driver (Honda Accord). The problem you're going to face is weight. Combining the weight of both gas and electric powertrains in one vehicle severely compromises both. The only way to even begin to balance the equation, that I have found, is spend a LOT of money on the highest energy density lithium batteries available.

The best case scenario I found was just to build a stop-n-go traffic boost system, so I wouldn't have to wear my left leg and clutch out in heavy city traffic. With a 100lb 8-9-inch motor, limited-range (small) lithium battery pack, and some creative weight saving measures, I figure I could keep it very close to the stock weight. Otherwise, the fuel economy of the ICE is reduced by having to tug the electric powertrain (when it's not providing assistance), and the range of the electric is severely compromised by having to move a heavy ICE vehicle. It just doesn't make sense, any way I slice it, for my needs.

I'd be better off buying a vehicle with an automatic, and performing the aforementioned creative weight saving measures. Better fuel mileage, better handling, etc. Probably why the factory Prius only has enough batteries for a few miles... I wonder how much weight the electric drive components add to the car. It would be interesting to strip one of them and see what the mileage and performance difference is.

Sorry, back on subject. It comes down to what you really want to accomplish. It has to be more of a "green" and/or technological pursuit. It's not going to pay off in terms of efficiency, so you have to be looking for a different reward.


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## terra (Mar 8, 2010)

toddshotrods said:


> I have been toying with this idea for almost two years now for my daily driver (Honda Accord). The problem you're going to face is weight. Combining the weight of both gas and electric powertrains in one vehicle severely compromises both. The only way to even begin to balance the equation, that I have found, is spend a LOT of money on the highest energy density lithium batteries available.
> 
> The best case scenario I found was just to build a stop-n-go traffic boost system, so I wouldn't have to wear my left leg and clutch out in heavy city traffic. With a 100lb 8-9-inch motor, limited-range (small) lithium battery pack, and some creative weight saving measures, I figure I could keep it very close to the stock weight. Otherwise, the fuel economy of the ICE is reduced by having to tug the electric powertrain (when it's not providing assistance), and the range of the electric is severely compromised by having to move a heavy ICE vehicle. It just doesn't make sense, any way I slice it, for my needs.
> 
> ...



Well I'll have shaved a couple hundred pounds in just body panels, and quite a bit more in interior weight saving too. Ideally I'd like to have an electric only option up to 20mph, then kicking on the V8. If I can just cut the stop and go city driving out of ICE duty, I figure I can save quite a bit of fuel. Or maybe the motor wouldn't have enough battery to power the car for more than a couple miles, in which case it would just be dead weight.

How would I go about pairing them though?


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## toddshotrods (Feb 10, 2009)

terra said:


> ...Or maybe the motor wouldn't have enough battery to power the car for more than a couple miles, in which case it would just be dead weight...


That's what I was trying to say (in my usual longwinded way). To have enough juice to last long enough to make it worth having the electric setup on board, you're going to have quite a bit of weight. The batteries that have a high enough energy density to come close will cost thousands.

The other issue you have is starting with a relatively heavy vehicle. Your weight shredding goals are just going to bring you closer to what the typical type of conversion vehicle (small) would weigh, then you add the electric stuff.





terra said:


> ...How would I go about pairing them though?


With a front-engine/rear-drive vehicle like yours, I would just put the electric motor between the transmission and rear differential. You'd need a motor with dual shafts, an adapter to mate the front shaft to the tramsnission output, and a custom driveshaft to mate the motor's rear shaft to the diff (could be a modified BMW part). That should put the motor between the front seats, which keeps some of the mass centered in the vehicle. A TransWarp 11 would be excellent for this, but you'd need to do some calculations to make sure the motor isn't spinning too fast when the engine is at its max rpm in the highest transmission gear. You could also ask Netgains how fast the motor can be safely spun when it's not making power.


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## terra (Mar 8, 2010)

toddshotrods said:


> That's what I was trying to say (in my usual longwinded way). To have enough juice to last long enough to make it worth having the electric setup on board, you're going to have quite a bit of weight. The batteries that have a high enough energy density to come close will cost thousands.
> 
> The other issue you have is starting with a relatively heavy vehicle. Your weight shredding goals are just going to bring you closer to what the typical type of conversion vehicle (small) would weigh, then you add the electric stuff.
> 
> ...


Ya I understand. I don't mind spending thousands on batteries, the new M3 engine was close to $40k alone. The chassis was substantial as well. But if I can't get over 3 miles on electric, the project is pointless. At that point I might as well focus on weight reduction and trying to get a bit more efficiency out of the ICE.


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## toddshotrods (Feb 10, 2009)

If you're willing to spend a good bit for good batteries, you may be able to come up with a reasonable compromise. You can get more than 3 miles of range. I just referenced the Prius' limited range to make a point. 

Like I said though, whether it's worth it depends on your goals. If you're trying to save money in fuel - you're going to spend enough building it to buy addiitonal fuel for a long time! If you're interested in saving fuel to _save the planet_, it may be worth it to you. I you just want it for what it represents/means to you, it may be worth it.


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## terra (Mar 8, 2010)

toddshotrods said:


> If you're willing to spend a good bit for good batteries, you may be able to come up with a reasonable compromise. You can get more than 3 miles of range. I just referenced the Prius' limited range to make a point.
> 
> Like I said though, whether it's worth it depends on your goals. If you're trying to save money in fuel - you're going to spend enough building it to buy addiitonal fuel for a long time! If you're interested in saving fuel to _save the planet_, it may be worth it to you. I you just want it for what it represents/means to you, it may be worth it.



What's a good bit when it comes to batteries? The requirements for the car are a bit odd, but any MPG is an improvement, regardless of cost (within reasonable limits obviously). If I can average 30 mpg combined in normal driving I would be thrilled. Obviously less when operating hard in just ICE.


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## toddshotrods (Feb 10, 2009)

I think I remember seeing figures between $5 & 10K for the LiFePo4-based packs. I'm not positive about that, and don't really know the weight. Performance would be mediocre (using high-performance as the goal) because they aren't capable of delivering massive doses of current - better for commuter cars.

I am planning to use A123 cells in my race rod. It's only supposed to weigh 1200lbs complete, and the whole concept is based on keeping the weight to a bare minimum. My pack will weigh around 400-500lbs with charger, BMS, cases, connections, etc. It will be around 330v/2000amps. It will cost $20-25K, and I have to almost be capable of magic tricks to make it happen, because A123 doesn't sell to the general public. It's worth it to me because all I care about is performance, and they offer the highest energy density of currently available (sort of) cells. I think the same size pack, with regard to volts and amps in Headway cells would weight about twice as much, but probably cost a little less - not sure because I never did the math and priced it.

Because my vehicle is so light, I may be able to squeeze 40-50 miles from it (it's all electric), but range wasn't my goal. I didn't care if it could only go 5 miles, as long as it was extremely fast for those 5. The potential extra range is a by-product of a pack big enough to race with. I don't really know what the watt-hour requirement of a vehicle your size and weight would be, but I would assume you would get no more than half the range I would.

So, using a setup similar to mine as an example, you would gain 750-1000 pounds and be able to do 20 miles on electric, for $20-30K. You can increase the size of the pack, adding more weight and cost, for more range; or you can decrease the cost of the pack with lower-cost cells which will add more weight with less performance. What you really have to do is start coming up with hard numbers to see if there is a happy medium that would give you what you want. If you end up with a 6,000lb land barge that has horrible fuel mileage and performance, you won't be happy. If you end up with a $50-75K project that has decent performance and mileage, you _might_ be happy - depending on what your looking for.

You have to do the math to even begin to know.


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## terra (Mar 8, 2010)

Thanks for the help man. From the sounds of it, that's not the ideal way for me to go. Let me pose this question then, what kind of options do I have for a full electric vehicle without losing all performance? Dropping the $40k ICE gives me quite a bit of wiggle room for electric motor options. You mentioned a battery company earlier that only sells to companies? I can buy through my company, so that would be an option for me if the batteries are worth it. What kind of motor would I need, and what battery pack would give me 200 mile range?


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## deelymc (Jul 7, 2010)

What about using a used nimh battery pack from a prius? They cost around $500.


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## CroDriver (Jan 8, 2009)

deelymc said:


> What about using a used nimh battery pack from a prius? They cost around $500.


Too weak, not enough energy. 

You could install a electric motor between the V8 and the transmission. I think that this wouldn't be very difficult, you just have to choose a motor with a similar RPM range. A AC motor/controller setup would be the best option. You could charge the batteries while cursing with a little load on the V8 trough regen breaking with the electric motor. The ECU would "think" that the car goes up hill and you wouldn't need to change anything on the ICE or his "brains". This would be a very cool setup.

I would be willing to make that for you with no development costs. This could be a very nice adapter kit for retrofitting all kinds of BMW-s.

The liquid cooled AC motor we're developing would fit nicely between the engine and the gearbox. We would just need a adapter housing, a shaft and new motor mounts. I think that the V8 is short enough to fit in the 5-series (E60 or F10?) engine compartment with our 24 cm long, 200kW (272 hp) electric motor between it and the gearbox. The M5 has a V10 that's quite a bit longer than the V8. The straight 6 cylinders are even longer.










If I where you, I would use flat A123 cells (VERY VERY hard to get since I bought all 600 that where available  ). They would be very light and the only option for 200kW of electric power anyways (high power density).

A DC motor would be a lot cheaper but they are usually quite long (because of the commutator) and you would have to charge the batteries on the socket since DC motors can't* charge your batteries. And the cooling would be a big problem. 

_*You can find a lot of discussion on the DC regen topic around here. Long story short: too complicated - no controller supports it but it's theoretically possible. _


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## CroDriver (Jan 8, 2009)

Some numbers:

*Weight*

Motor 62 kg
Inverter 8 kg
320V/20Ah batterie 48 kg
Other stuff (mountings, housing etc.) 15 kg
*Sum 133 kg*

6,4 kWh stored energy
42 miles all electric range @ 150 Wh/mile consumption and 100% DOD
35 miles realistic range
1 hour charging time with a 20 AMP/220V socket (from 80% DOD)
1/2 hour charging time with a 40 AMP/220V socket (from 80% DOD)
20 minutes charging time with a 70 AMP/220V socket (from 80% DOD)

This sounds a lot better than the Volt


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## deelymc (Jul 7, 2010)

That does look like a great setup. Would the motor work as an assist motor?- I think its called parallel or series. so 300kw v8 + 200kw electric motor= 500kw?


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## CroDriver (Jan 8, 2009)

deelymc said:


> That does look like a great setup. Would the motor work as an assist motor?- I think its called parallel or series.


This is a parallel hybrid setup. It's similar to the Prius setup but with stronger electric components, without a CVT transmission.



deelymc said:


> so 300kw v8 + 200kw electric motor= 500kw?


Yes, theoretically.

But this is not a easy project, I doubt that many people tried this... Even big companies sometimes fail to make something like this work.

@ Terra: What transmission do you want to use?


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## terra (Mar 8, 2010)

Crodriver I owe you big. I'll probably be using the 7 speed BMW transmission, but I'm not set on it. I plan on using the V8 out of the M3 in a 5 series body. I think that would take the last amount of space with the greatest power. Is this something that could be duplicated, as I'm not just looking for 1 set to be honest. Email me if you'd like to discuss this off the forum.


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## JRP3 (Mar 7, 2008)

CroDriver said:


> This sounds a lot better than the Volt


Not sure about that. The Volt has a 16KWH pack and only uses half of that for 40 miles of range, so it will last a lot longer than the 6KWH pack you propose.


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## toddshotrods (Feb 10, 2009)

terra said:


> ...Is this something that could be duplicated, as I'm not just looking for 1 set to be honest...


Looking at a potential hybrid biz venture eh? That makes the questions and ideas make more sense.


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## CroDriver (Jan 8, 2009)

JRP3 said:


> Not sure about that. The Volt has a 16KWH pack and only uses half of that for 40 miles of range, so it will last a lot longer than the 6KWH pack you propose.


A123 claims 15.000 cycles @ 80% DOD. That would be a lifetime of 525,000 miles with a 35 mile range. Even half of that would be very good.

Terra - p.m. sent

Todd - yeah, it wouldn't be bad to produce something for the "mainsteream" market. A good kit at a reasonable price could really help to bring more (PH)EVs on the road


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## toddshotrods (Feb 10, 2009)

CroDriver said:


> ..If I where you, I would use flat A123 cells (VERY VERY hard to get since I bought all 600 that where available  ). They would be very light and the only option for 200kW of electric power anyways (high power density)...





CroDriver said:


> A123 claims 15.000 cycles @ 80% DOD. That would be a lifetime of 525,000 miles with a 35 mile range...


What's the deal with their flat cells. If you bought the only ones available, does tht mean they're no longer in production?

What's the highest C-rate? Come on share brother!


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## JRP3 (Mar 7, 2008)

CroDriver said:


> A123 claims 15.000 cycles @ 80% DOD. That would be a lifetime of 525,000 miles with a 35 mile range. Even half of that would be very good.


Good point, forgot you were talking A123. Since all the pouch cells "dried up" they don't exist in my world


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## JRP3 (Mar 7, 2008)

toddshotrods said:


> What's the deal with their flat cells. If you bought the only ones available, does tht mean they're no longer in production?
> 
> What's the highest C-rate? Come on share brother!


They're still being produced, we just have to wait for another batch to "fall off the truck"  They may be keeping a closer eye on them now


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## toddshotrods (Feb 10, 2009)

JRP3 said:


> ...we just have to wait for another batch to "fall off the truck" ...


Where's the truck taking them, _i.e._ what production item are they being used in?


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## JRP3 (Mar 7, 2008)

Eaton, Navistar, Fisker, probably others.


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## terra (Mar 8, 2010)

toddshotrods said:


> Looking at a potential hybrid biz venture eh? That makes the questions and ideas make more sense.


Sure..let's say, "potential."


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## CroDriver (Jan 8, 2009)

Todd, they're still in production but not available for the market. Someone from A123 told me that they're in the testing phase - that was maybe 6 months ago.

I hope that they will sell them directly to me once they see what we want to do with them 

15C continuous, 25C peak (my test results)


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## toddshotrods (Feb 10, 2009)

CroDriver said:


> Todd, they're still in production but not available for the market. Someone from A123 told me that they're in the testing phase - that was maybe 6 months ago.
> 
> I hope that they will sell them directly to me once they see what we want to do with them
> 
> 15C continuous, 25C peak (my test results)


Thanks Cro.  Sounds like you're having fun over there!


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## CroDriver (Jan 8, 2009)

toddshotrods said:


> Thanks Cro.  Sounds like you're having fun over there!


Yeah, I'm on vacation after all












Have fun there in the US and A


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## toddshotrods (Feb 10, 2009)

Dude, you build a mean racer but if you're going to take great scenic pics you gotta learn to frame them!


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