# Planning: an Ultima(te) EV performance car



## j-rho (May 29, 2019)

So much great know-how here, my thanks in advance for allowing me to tap into it! 

As background, I'm a classic gear-head and have built/tuned lots of cars for amateur motorsports (autocross and track), sometimes successfully  For the past couple years I've been daily driving - and occasionally towing - with a Model X, and have fallen in love with the simple, effortless, and drama-free nature of EV power. For my next performance-car build, I'd like to do an EV.

While the Model 3 Performance does extremely well for what it is, the ability to bring performance to a higher level is fairly limited. What I'd like to do is start with a lightweight tube-framed chassis and body with performance-focused aerodynamics, and modify it to run a high-performance EV power system.

Specifically, I'd like the car to be able to handle 3 full laps at any normal race track (say 6-8 total minutes) without overheating and/or suffering major performance degradation. For those familiar, a Time Attack. It's also gotta be able to do 3 laps again about 3 hours later, where at best a 10-20kw charger will be available between session. The Model 3 in Track mode can do this today, the S/X cannot even complete one lap before drastically falling off.

My budget is probably higher than most DIY hobbyists, but not to where it's a business writeoff. What I've found is there's a huge leap in costs as you go beyond the mass produced stuff. A whole 100Kwh Tesla battery is about $25k, and the Model3 PM perf drive units are like $8k each. So for the big heavy parts, you're under $50k for a 3-motor system with inverters and reduction gears. 

The next step up, everything gets like 5x as expensive? $25k motors, $15k+ inverters, and you still have to do the gear reduction yourself? I've asked a couple battery companies for quotes but am afraid at what I'll get back. Feels like it's going to be $250k, or 5x the top-shelf Tesla parts.

My going-in thought is a full 100Kwh worth of the 6.3kwh Tesla modules, and either 2 (1 front 1 rear) or 3 (1 front, 2 rear) Model3 PM rear motors. They've been shown to put out 270kw in the Model Y Performance. One session of 3 laps should draw between 20-40% of the charge, depending on the track. Would run as much AC chiller as I could to try to keep things cool enough for those 6-8 minutes.

I know there's a ton I'm missing here. An area of concern is whether or not the Tesla battery can supply sufficient amperage to run 3 of those PM motors. If not, at some point it makes more sense to stick with 2 motors as there's also a weight savings which helps everything that isn't outright acceleration.

There are probably a ton of other things too! Fill me in! For a budget of $50-75k, are there better options than the Tesla components?


----------



## brian_ (Feb 7, 2017)

This sounds like an interesting project. It also sounds like you at least started with the idea of using an Ultima as the base vehicle - is that still the plan? It's really not suitable for the AWD configuration.

Even with an optimal tube frame and minimal bodywork, anything with a full 100 kWh Tesla battery pack, three (or even two) motors and gearboxes, and all the required supporting equipment will not be light.

Is the plan for track-only use, trailered to the track? That makes a lighter car more feasible, by removing some road vehicle equipment requirements and avoiding an onboard charger.

I agree that using any commercially available aftermarket motors, controllers, or gearboxes massively increases the price.


----------



## j-rho (May 29, 2019)

Thanks for the reply brian_! Always enjoy reading your posts.

You are absolutely right, AWD will not be easy. Thankfully I am rather short and can probably live with the front firewall & pedals moved back several inches to allow for a motor to run in its natural orientation. If not, can look to run it inverted and deal with the consequences to cooling system space. In either case there remain the challenges of fitting uprights which can receive drive, and fitting a pushrod-style spring/damper system to make room for the halfshafts. Plus the darn steering rack, fun!

What I hope/believe would make all that worth it, is the ability to better accelerate in inclement weather (of which there is always some) and the ability to perform lots more regen.

The intended use of the car is the One Lap of America. It's a series of time-attacks (plus skidpad, autox, and drag-racing) held at different tracks over several days. I ran it last year in a Viper ACR and had a blast. There were two teams that year in Teslas (one a P100D, the other a M3P) who I spent a lot of time talking to. Bought a C8 Corvette to run it again this year, but the event was cancelled due to Covid. Sold the C8 yesterday (compared to an EV it's not that great!) so now have some budget, garage space, and thanks to Covid - time! available to get started on something like this.

And right again - yes an Ultima RS. I love how they look, and one should be just barely streetable enough for this use (the event has been done before in ICE Ultimas). A lot of their natural shortcomings (noise, heat) should be mitigated going electric. Some have been built with supercharged LS engines and AC at under 2100 pounds; I'm hopeful I could get a 100kwh (~1000lbs.) 3-motor (~600lbs.) one at or under 3000 pounds, or ~900 pounds heavier. The hope is that over time as battery tech improves, the car gets lighter, with longer range, and more power available to the motors.

One Lap has 500-600 mile transits between tracks each day where the car must be driven, it cannot be trailered. As I won't be able to use the Supercharger network, will need some kind of "power trailer". Have some thoughts on that but it could be a whole separate thread.


----------



## brian_ (Feb 7, 2017)

It looks like you have a good handle on the many issues. 

Yes, a battery or generator trailer is probably better in a separate thread, as long as it is clear here that the car itself doesn't need much range.


----------



## Tremelune (Dec 8, 2009)

To go faster than a Tesla for the price of a Tesla involves starting with a Tesla. You're not going to see revolutionary kW-per-Kg improvements in batteries year over year...More like decade by decade.

I gotta wonder how much faster this Cobra is around a curvy track than a bone-stock Model 3 Performance with 1,000 pounds of interior and HVAC removed...and that's without trying to get more power out of the Tesla stuff (which people are doing with custom controllers and what not):









Model 3 Battery Pack for Tesla Cobra EV


We decided to build a 3rd generation battery pack for our Tesla Cobra EV road race car. Our 1st pack was from a 2015 Kia Soul EV. It had very high power output (we were able to pull 375kW), but the capacity (27kwh) was a little short for our 20 minute races. We replaced it with 2/3 of a...




www.diyelectriccar.com





Another reality to consider is that, in two years, when you can get a Taycan for $75k, do you still want to be tweaking the power trailer integration or working out the bugs in the suspension of your custom rig...?

I, too, spend much money just to spend time building something fun...if that's a big part of your goal, have at it!


----------



## j-rho (May 29, 2019)

Have followed the Cobra for some time, great to see. Some of the design positions I hold are based in part on his experiences - using the PM motors instead of induction motors, and using water-cooled batteries, even if they don't offer the same "stiffness". Thankfully my use case of 6-8 minutes of high output is only about 1/3 of the Cobra's 20+ minute stints. I do want at least 2x the power though.

The Taycan is great in lots of ways and I have some friends who performed certification testing for Porsche in the Turbo S. For my use case the absence of a robust high-speed charging network would be a problem, and likely still necessitate some kind of trailer. Plus in a few years, it will still be well over 5000 pounds and look like a 911's overweight cousin 

If the Model S Plaid or Roadster were available today, and particularly if they were available in some kind of hardcore track spec, I might reconsider my position. Not going to pull the trigger one way or another for a month or so, though I suspect we probably won't hear any big product announcements from Tesla until next year. The OE options will always be better thought through and engineered than what I could do at home, but they'll also always be a lot heavier and more compromised. If it weren't for the surplus of time these days (and for the foreseeable future) to do big projects at home, I'd be more inclined to shy away from the DIY approach


----------



## joekitch (Sep 13, 2013)

i'm a big advocate of ditching range but keeping power, and factoring in some dc fast charging into the build.
100 miles of range isn't so bad if you can fast charge in a pinch, it just won't road trip
but 100 miles of range worth of batteries is far cheaper and far lighter than like 300 miles of range worth

keep the weight low and the power high with an awd configuration, and you'll make an absolutely vicious track weapon


----------



## j-rho (May 29, 2019)

I’d be open to other batteries - especially if the overall package were smaller and lighter! And could be kept cool. It feels like the LG Chem stuff has potential but one would need to go to great lengths with all manner of custom cooling plates to approach the OE level of cooling the Tesla batteries have. And by then its size and weight advantages are minimized. With the three motors there is room to use a 400v battery than can provide like 2400 amps. It’d still need at least 50kwh usable to get through a session also. 
I put in a request to the EV Drive company for something like what they built for the Palatov car, but have a feeling it’s gonna be a 6 figure deal, haven’t heard back yet. 

Car will need some kind of range extending trailer in any case.


----------



## joekitch (Sep 13, 2013)

Chrysler pacifica hybrid batteries perhaps, or chevy volt batteries 
both of those have very good power density, although not great energy density, and the volt cells at least have cooling essentially built in


----------



## Hollie Maea (Dec 9, 2009)

We can build power dense battery modules for around $700 per kWh. That’s way more expensive than salvage packs, but no OEM batteries are designed for high sustained power, not even Tesla.


----------



## joekitch (Sep 13, 2013)

people are getting incredible performance out of Chevy Volt packs in terms of power density, you can absolutely smash amps out of them and they don't even blink
also the pacifica hybrid packs are about as good, ev west uses them in their 675ph pike's peak ev bmw


----------



## brian_ (Feb 7, 2017)

Hollie Maea said:


> We can build power dense battery modules for around $700 per kWh. That’s way more expensive than salvage packs, but no OEM batteries are designed for high sustained power, not even Tesla.


A challenge in battery configuration is always finding the right size, shape, capacity, and capability of modules to suit the vehicle. I don't want details to fill up this thread if the builder (j-rho) is not interested in them, but is there a website or document with more information about specifically what configurations can be built? For instance, in a stack of pouch cells the cell dimensions constrain two dimensions of the module - is there a choice of cell sizes? The balance between capacity and physical pack size (for a given cell) is determined by how many cells are used in parallel - is that selectable by the customer? Power density is limited by (among other factors) the cooling system - are modules available with a choice of interleaved fluid-filled fins, or set up for chill plates on one side or two? I don't see any of this on the EV Drive website; the Battery Modules product page just says "Product listing coming soon…".


----------



## brian_ (Feb 7, 2017)

j-rho said:


> I’d be open to other batteries - especially if the overall package were smaller and lighter! And could be kept cool. It feels like the LG Chem stuff has potential but one would need to go to great lengths with all manner of custom cooling plates to approach the OE level of cooling the Tesla batteries have. And by then its size and weight advantages are minimized.


Almost everyone using Tesla (any model) and Chevrolet Volt modules uses the OEM cooling system, because it is internal to the modules. This is certainly an advantage of these modules, both for performance and for ease of installation.

It appears that almost no one using the modules from any OEM EV with a chill plate system (including the LG Chem modules from the Chrysler Pacifica) uses the OEM chill plates. That makes sense in the case of a single chill plate for a large under-floor pack which doesn't fit in the conversion vehicle, but the Pacifica has a relatively compact pack, and it doesn't seem like anyone has even looked to see if it is one big chill plate (which might still fit some projects) or perhaps two 3-module plates. It might be worth having a look.


----------



## Hollie Maea (Dec 9, 2009)

brian_ said:


> A challenge in battery configuration is always finding the right size, shape, capacity, and capability of modules to suit the vehicle. I don't want details to fill up this thread if the builder (j-rho) is not interested in them, but is there a website or document with more information about specifically what configurations can be built? For instance, in a stack of pouch cells the cell dimensions constrain two dimensions of the module - is there a choice of cell sizes? The balance between capacity and physical pack size (for a given cell) is determined by how many cells are used in parallel - is that selectable by the customer? Power density is limited by (among other factors) the cooling system - are modules available with a choice of interleaved fluid-filled fins, or set up for chill plates on one side or two? I don't see any of this on the EV Drive website; the Battery Modules product page just says "Product listing coming soon…".


I don't want to turn this thread into an advertisement for our modules, but I'll do one post answering your questions since they could be relevant to OP. Let me know if you want me to delete these, OP.

Our modules use 21700s, so one dimension is always about 76mm. Apart from that, the small size of the individual cells gives a lot of dimensional flexibility, and our method is such that we can do different configurations fairly easily. We usually embed BMS in each module, and so in the past we have typically done 12S modules to fit that, but we're developing a 14S BMS so we'll be doing more of those in the future. We have done anwhere from 30Ah to 144Ah but there aren't too many limitations there, apart from the modules becoming too big to be managable. We have a high power cell that we usually use but can use energy cells as well if really needed. As far as cooling goes, we pull the heat out to aluminum surfaces such that it can be cooled via liquid coldplates or air fins or just by conduction to the battery box.

Sorry about our website, we've been working on a bunch of projects the last couple of years and have been slow getting the standard products out there. Two projects that have used this module design have been the Palatov/Cascadia racecar that did Pikes Peak last year. That one had a 79 kWh and dynoed 1300 hp at the wheels. Also the Webasto Mustang Lithium from SEMA last year had them, though it has not been tested to full power yet due to a motor issue.


----------



## j-rho (May 29, 2019)

Please type away Hollie Maea! I read your posts in the Palatov Pikes Peak thread, which lead to me filling out an interest for on your website. The price is a bit more reasonable than I'd anticipated. Is there a way I can contact you or your company for more info?


----------



## Hollie Maea (Dec 9, 2009)

j-rho said:


> Please type away Hollie Maea! I read your posts in the Palatov Pikes Peak thread, which lead to me filling out an interest for on your website. The price is a bit more reasonable than I'd anticipated. Is there a way I can contact you or your company for more info?


You can email me directly at PAULL AT EVDRIVE DOT COM


----------



## TPNxl (May 1, 2020)

Someone correct me if I'm wrong, but you might be able to keep the LS in addition to the electric motors? Essentially your setup looks like this:

Normal EV drive setup, likely 2 Tesla rear performance motors, one at each end of the car
LS mounted using stock mounts, intake, ECU, everything, likely tune for torque vs power
Instead of a transaxle hook up a generator to the LS. Take the power from the generator and pour it into the motors.
Have a small 100+ C battery (a few kWh) to absorb the generator output differences and to give maximum power to the motors when needed, and use the LS to recharge these batteries and power the car in every other situation.
With this setup, instead of having 1000lb of batteries or more you now have a 500lb LS (with fuel tank, intake, etc), 100lb of batteries, and a 200lb generator. Plus you can refuel in minutes vs hours.


----------



## joekitch (Sep 13, 2013)

that's a serial hybrid setup, if the engine isn't connected to the wheels
and at that point you're much better off with an engine designed to do that, like a chevy volt engine
but there's a lot of extra software and controlling needed for that kind of setup


----------



## TPNxl (May 1, 2020)

Well I suggested the LS because there are versions designed for torque, it fits in the Ultima chassis without modification, and the Chevy Volt engine isn't powerful enough for what the OP is suggesting. Of course it could work with any sufficiently powerful engine.


----------



## brian_ (Feb 7, 2017)

Hollie Maea said:


> Our modules use 21700s, so one dimension is always about 76mm. Apart from that, the small size of the individual cells gives a lot of dimensional flexibility, and our method is such that we can do different configurations fairly easily.


I guessed that you were using pouch cells based on the website images - apparently I guessed incorrectly, because I didn't notice the high parallel cell count indicating the small cells.

As explained above, that means that the module thickness is constrained, with the other dimensions being relatively flexible, although to avoid every customer getting a custom product there would need to be some standard sizes.



Hollie Maea said:


> We usually embed BMS in each module, and so in the past we have typically done 12S modules to fit that, but we're developing a 14S BMS so we'll be doing more of those in the future.


I think it would be nice to have the option of fewer than 12 cell groups in series, to allow for more modules (for the same total capacity and pack voltage) for more flexibility in packaging without making every module uniquely shaped to fit its mounting location.



Hollie Maea said:


> As far as cooling goes, we pull the heat out to aluminum surfaces such that it can be cooled via liquid coldplates or air fins or just by conduction to the battery box.


The cooling design sounds like the same approach as Rivian.


----------



## brian_ (Feb 7, 2017)

TPNxl said:


> Someone correct me if I'm wrong, but you might be able to keep the LS in addition to the electric motors? ...





joekitch said:


> that's a serial hybrid setup, if the engine isn't connected to the wheels...


Yes, that's a pure series hybrid, and compared to a conventional mechanical transmission system it is heavy and it transmits the engine's power inefficiently. There are advantages to hybrids, but whether they are worthwhile or not, this just isn't an EV. I don't think it addresses the desired characteristics of the project.


----------



## Hollie Maea (Dec 9, 2009)

brian_ said:


> As explained above, that means that the module thickness is constrained, with the other dimensions being relatively flexible, although to avoid every customer getting a custom product there would need to be some standard sizes.


That's right. We'll have standard offerings that I think will suit most people. The first standard one I'm working on will be about 100Ah and 14S. That should be a pretty good size for a lot of projects I think...a 700V performacne system would be about 71kWh and a 350kWh system would be 35kWh. Other sizes to follow, plus the opportunity for custom versions.



brian_ said:


> I think it would be nice to have the option of fewer than 12 cell groups in series, to allow for more modules (for the same total capacity and pack voltage) for more flexibility in packaging without making every module uniquely shaped to fit its mounting location.


Exactly. The most recent project we did was 6S, and we've done others as well. Only real downside is that it's not as efficient at utilizing the embedded BMS boards so you need extra slaves. I'm also actually working on a design for a 1MWh string in which the individual modules will just be 1S (Obviously you don't embed BMS at that point). I guess in a way that's just a "prismatic" albeit with cylindricals inside...


----------



## j-rho (May 29, 2019)

Would like to thank Hollie Maea for taking the time to answer my questions over email, even for this prospective customer who is months away from being at a purchase point. Great pre-sales support from EV Drive gives confidence in there being quality support after the purchase.


----------



## rmcdaniels (Jan 17, 2017)

We built a Power Trailer for a 1500-mile road rally in our EV. I also used it on a 1000-mile road trip to the Amelia Island Concours. It's not a perfect solution, but it got the job done:


----------



## joekitch (Sep 13, 2013)

rmcdaniels said:


> We built a Power Trailer for a 1500-mile road rally in our EV. I also used it on a 1000-mile road trip to the Amelia Island Concours. It's not a perfect solution, but it got the



yours might be the only functional gas generator trailer I've ever seen on here

what's the GVWR?
what's the tongue weight?
can it fully supplement your watt hours per mile usage? As in, you never need to charge, just run the generator while driving?
how is it wired relative to the batteries and motor and inverter? Like, is it wired parallel to the motor as like a "Second battery?" Or is it wired into the charge controller and its like a charger that's continuously plugged in?


----------



## rmcdaniels (Jan 17, 2017)

joekitch said:


> yours might be the only functional gas generator trailer I've ever seen on here
> 
> what's the GVWR?
> what's the tongue weight?
> ...


Generator and trailer weigh about 600 pounds. Tongue weight is negligible, I balanced it on the trailer pretty well. It's not particularly noticeable when driving, but I've got a lot of regen programmed in so my braking is very good. I also have a lot of relatively heavy i3 batteries in it now for long road rallies, so it's a bit porky.

It's wired into an eMotorWerks 12kw charger, which is the real limiter in the system, and we run it while driving. The output of the charger is parallel to the traction pack. Up to about 50 MPH you can run off the generator, and above that it pulls from the traction pack and the charger. For long trips we tell Google Maps to avoid highways and we can go for hundreds of miles without stopping. Even if it gets a little low, with 12kw charging we just stop for a bite to eat and it charges it back up pretty quickly. When I went to Amelia Island for the Concours (about 500 miles), I easily made it 380 miles solo on day one and the charge never got very low; I just stopped because I was tired and wanted to get to bed early.


----------



## MattsAwesomeStuff (Aug 10, 2017)

rmcdaniels said:


> We built a Power Trailer for a 1500-mile road rally in our EV.


Tell us more!

What wattage is the generator?
How many watt-hours per mile does your car typically consume at 50mph?
How many watt-hours per mile did you car consume at 50mph when towing the trailer?
How big was the gas tank?
How long at highway speeds did the gas tank last?


----------



## rmcdaniels (Jan 17, 2017)

Generator is good for 15kw continuous. It's this one: Generac Power Systems - 15000 watt GP Series Portable Generator with Electric Start - 5734

It holds 16 gallons of gas and uses close to 3gph at 12kw.

It's been a while since I did the math on energy usage and trailer towing, but As I recall you use about 5kw to tow a trailer like that, maybe less. What we observed was that if you kept it under 50mph, then you could pretty much go all day. Even that varied, traffic and a few stop signs/lights would extend that while continuous steady-state speed could cause a slow drain on the pack. If I went 70mph on the Interstate, then I could get a couple of hundred miles before stopping for a few hours to charge up a really run-down pack. I basically tried to keep it slow, go 100-200 miles, take a short break and top it off, and then do it again. On a good day I could do 2-3 stints like that.


----------



## MattsAwesomeStuff (Aug 10, 2017)

rmcdaniels said:


> Generator is good for 15kw continuous.


Hrmph.

I picked up a 4000 watt generator for this purpose a couple years ago.

But at 5kw drag on a trailer, it won't even cover the added energy of pushing itself down the road.

Good to know though. Thanks.


----------



## rmcdaniels (Jan 17, 2017)

Yeah, I tried mounting some smaller generators in the car with mixed results, but having a big running generator in the car with you is pretty much unbearable.


----------



## joekitch (Sep 13, 2013)

if you guys want to upgrade that generator at some point, the chevy volt's engine has a built in generator transaxle thing and it claims to deliver 55kw continuous electrical, that'd keep that car topped off at all speeds no problem. You can pick up Volt engines from wreckers for like a grand all-in, not bad

of course then the problem is making a charger which can accept those kinds of KWs constantly

or wiring the system to take power from both the generator and the batteries in parallel while the car is in motion, maybe have it cut off when you're driving slower than 40mph

this is something i've been thinking about for a while, but i don't have the electrical engineering knowledge to really pursue it. It could make most any diy EV absolutely feasible as a year-round all-purpose car


----------



## rmcdaniels (Jan 17, 2017)

Bingo, without the budget to design/build a DC charging system, the charger is the limitation. I'm a little surprised at how well the eMotorWerks charger has held up to the abuse.


----------



## joekitch (Sep 13, 2013)

is wiring the generator in parallel with the batteries onto the motor not feasible?
so the motor pulls from the generator when it's available, but from the batteries when it isn't
again i'm not sure if this a thing which can work. But it must, since i think that's what the chevy volt does?


----------

