Lemons launches EV class - and $50k prize for overall race win in an EV!

ProDarwin said:

I think you would need a water-cooled setup to dissipate that kind of energy.  Probably easy for battery & inverter, I'm not sure how many of the motors in EVs are water cooled?

I think most of them are oil-cooled, inside the case... that way you get the improved bearing life, and none of the water-electron hazardous interaction.

ironically... I reckon a gen2 Prius is probably the "ideal" starting shell... cheap/available, good aero, and already has a battery rack in the trunk.... and more space for electrons than the gen1 insight.

In reply to ProDarwin :

All of them are water cooled.  They all have a water-to-case heat exchanger, then conduction and/or oil from the case to the stuff inside(motor windings and rotor) that gets hot.

sergio said:

How are all the electrical components going to handle the heat of running mostly flat out for hours? In real world driving all cars run around at part throttle most of the time, even EV’s. 

I think that is going to be as big of a challenge as anything else.  Heat.  There's a Dodge Omni 024 Jet Electrca that has made some appearances recently at LeMons.  Been at a few of the races it attended.  My understanding is that heat has been one of the biggest issues they've had.

...there is a whole series dedicated to this.  I bet a formula E car couldn't win this race with millions of $$$ from top manufacturers.  But some garage junky is going to for 50k?

Should be 50k to the first team to finish the race on full electric.  That or some % of the winners completed laps. That will still take a lot of ingenuity and would at least give a potential profit.

ProDarwin said:

IMO you need to do the floorpan like Tesla does, but you need to find a way to do a quick swap, which is going to be very very difficult, especially trackside. 

What if you somehow created a battery "tray" that bolted to the underside of the car.  Make sure to brace the body/chassis well enough that the batteries are not a stiffening item, i.e. the car could move (in theory) without the battery tray in place.  Then, come into the pits, jack up all four corners of the car, unbolt the tray, roll it out, roll another under the car and bolt it in?  That would give you the entire floor as a battery compartment with a simple, on paper, way to swap them out.

The first thing I think of in this is a car I've wanted to build for a long time, but they're just too expensive to cut up.  Take a single cab VW truck and put an electric motor in the back connected to the stock transmission.  IIRC, there's some motor that's almost a direct bolt in.  Then fill the treasure chest area with batteries.  Put them on rolling shelves so they can be pulled out and swapped fairly quickly.  Bonus points if you mount a solar panel in the bed to kinda charge the batteries while driving. 

Granted, racing single cab VW truck would suck, but it'd be unique!

-Rob

sleepyhead said:

ProDarwin said:

I think you would need a water-cooled setup to dissipate that kind of energy.  Probably easy for battery & inverter, I'm not sure how many of the motors in EVs are water cooled?

I think most of them are oil-cooled, inside the case... that way you get the improved bearing life, and none of the water-electron hazardous interaction.

ironically... I reckon a gen2 Prius is probably the "ideal" starting shell... cheap/available, good aero, and already has a battery rack in the trunk.... and more space for electrons than the gen1 insight.

I agree the prius is a good idea for a starting point. plus you would get lemons points for theme and there are all kinds of things you could put on a sticker. "My local utility rolls coal so I can race my prius".

But in terms of battery, I'm thinking you would want them on racks that slide in and out of the vehicle. Like the back door and the rear hatch basically become like giant drawer faces. So you roll up next to the car with an empty battery cart, slide old batteries out of car and onto cart, and roll cart away, roll up with new cart, slide batteries in and go. 

I was originally thinking the low and flat floor of something like a minivan would be good for this, but the prius might be similar enough inside!

What about using an El Camino or Ranchero or small pickup truck? Then you could set the battery pack in the bed and use an engine hoist to lift them out and swap them in

^I would think having 1000lb of battery that high up would absolutely destroy handling.  Remember, you need to WIN overall, and you are up against some fast cars... that can go longer between pit stops.  

Floorpan seems to be a much better location.

What's the minimum pit stop time in Lemons again?

https://www.engadget.com/2019/03/03/piech-mark-zero-ev-sports-car/

Battery swaps require compromises. You have to place the battery someplace that makes it easy to swap quickly and easily which will cause issues with balance. I know that BEV power trains are far more common, but I think a hydrogen fuel cell powered vehicle could be worth investigating.

It would require no battery swaps, could refuel in a time similar to an ICE, and can have better range.

The fuel cell version of the Honda Clarity  fits the fuel cell and electric motor into the same amount of space as a traditional transverse V6/transaxle combo. It has a 366 mile range in normal driving conditions. If that gets cut in half under race conditions, I'd guess it would still be pretty comparable to most of the ICE stuff on the track.

Place the battery and fuel tanks where they're in the most optimal position (instead of having to swap out heavy batteries), and just refuel the thing like a normal vehicle.

GameboyRMH said:

What's the minimum pit stop time in Lemons again?

https://www.engadget.com/2019/03/03/piech-mark-zero-ev-sports-car/

woof!

let's take our 100ish kWh battery we theorized earlier in this thread. to charge it 80% in 5 minutes means 80 kWh * 60 minutes = 4800 kW of charging power. Or 5 megawatts. Or approximately 1371 honda 3500W portable gas generators working together. 

Edit, I think I did that wrong (unit analysis ERROR!) hold tight. Fixed now. 

ProDarwin said:

I think you would need a water-cooled setup to dissipate that kind of energy.  Probably easy for battery & inverter, I'm not sure how many of the motors in EVs are water cooled?

Chevy Volt packs are water-cooled but can be run without it. Tesla batteries are cooled partially via physics (the 18650 cells discharge less with heat, functionally limiting them to an extent) and a coldplate and big chunk of aluminum. Most prismatic cells- Nissan LEAF, BMW i3, Fiat 500e ect- also only use a coldplate with some using oil cooling, though I'd have to ask on Endless Sphere for good answers and mine is just offhand.

I reckon you're going to have to be at a track w/ Tesla superchargers (Summit has several at two of their tracks)... and monopolize them

also, I keep having daydreams about MB gullwing doors that pull the battery packs up and out of the car for removal

Robbie said:

GameboyRMH said:

What's the minimum pit stop time in Lemons again?

https://www.engadget.com/2019/03/03/piech-mark-zero-ev-sports-car/

woof!

let's take our 100ish kWh battery we theorized earlier in this thread. to charge it 80% in 5 minutes means 80 kWh * 60 minutes = 4800 kW of charging power. Or 5 megawatts. Or approximately 1371 honda 3500W portable gas generators working together. 

Edit, I think I did that wrong (unit analysis ERROR!) hold tight. Fixed now. 

I think you still got it wrong, that's 4.8mwm of total energy needed to get an 80% charge, regardless of how quickly it's put in. To get 80kwh into the battery over 5 minutes requires a charging draw of 960kw or 0.96 megawatts, which could be provided by just over 275 Honda 3500W portable gas generators, or just one of these:

Edot: 4.8mwm, not mwh

Klayfish said:

sergio said:

How are all the electrical components going to handle the heat of running mostly flat out for hours? In real world driving all cars run around at part throttle most of the time, even EV’s. 

I think that is going to be as big of a challenge as anything else.  Heat.  There's a Dodge Omni 024 Jet Electrca that has made some appearances recently at LeMons.  Been at a few of the races it attended.  My understanding is that heat has been one of the biggest issues they've had.

From their Roadkill.com article here, they were initially using lead-acids before swapping to 3 "Large" Chevy Volt packs. They had plenty of problems- why they thought those drone 'copter inverters from alibaba could ever handle fast charging I'll never know, and racing is literally the worst use for lead-acids no matter their age. Also their swap technique involves the batteries on a wood tray that's hefted out of the car. Not ideal.

sleepyhead said:

ironically... I reckon a gen2 Prius is probably the "ideal" starting shell... cheap/available, good aero, and already has a battery rack in the trunk.... and more space for electrons than the gen1 insight.

It might be, depending on how well you can get more of a "race" suspension to fit and work within it's original grocery-getting suspension- though there was a Jalopnik article on a madman who found he could work a set of Russian-made RAV4 springs in so he could go off roading(!).

Biggest problem is gonna be getting it to run all-electric alone. All Prius-es (sp?) use automatic transmissions because the electric motor also doubles as the starter and has to kick "on" at all times, which I don't think you could ever do with a manual. That motor is also ~30HP- not enough for racing- and is DC, which is also bad for anything other than going a single speed. You'll NEED to go AC just due to DC's inefficiencies when operating outside of it's zones, and then you're opening up all the wonderful problems of geometry that come with a complete engine and trans swap. Oh, and don't even THINK of having something interface with the CANBUS system in the prius- Toyota is horrible when it comes to their ECUs and cracks.

In reply to GameboyRMH :

Well, shoot. that's what I did first. 80kWh is the total energy you have to put in, and you only have 5 minutes to do it. 80kWh of energy in 1 hr (60 minutes) requires 80kW of power. to do it in 5 minutes you need 80*(60/5) = 960 kW. 

so yeah. 1 megawatt and only 300 generators. 

In reply to alfadriver :

During my ~year at an EV manufacturer, I had access to such a tool to calculate energy usage.  It was pretty interesting stuff.  The physics isn't hard, it's just a lot of calculations.  

One thing to remember is that any serious EV racer is going to absolutely require regen.  In theory, every race track is going to be zero net altitude change, so all the energy used going up will be reclaimed coming down, rinse and repeat.  Likewise, if the braking is managed properly, all the acceleration juice will get reclaimed in regen. 

Of course, that's all idealized, and there are transitional losses.  As well as frictional losses (aero, rolling) and those can e estimated pretty easily.    

Thermal management of the batteries is going to be a huge deal.  A winter race may be a requirement, even more so than picking the track with the lowest predicted power consumption.  

GIRTHQUAKE said:

ProDarwin said:

I think you would need a water-cooled setup to dissipate that kind of energy.  Probably easy for battery & inverter, I'm not sure how many of the motors in EVs are water cooled?

Chevy Volt packs are water-cooled but can be run without it. Tesla batteries are cooled partially via physics (the 18650 cells discharge less with heat, functionally limiting them to an extent) and a coldplate and big chunk of aluminum. Most prismatic cells- Nissan LEAF, BMW i3, Fiat 500e ect- also only use a coldplate with some using oil cooling, though I'd have to ask on Endless Sphere for good answers and mine is just offhand.

Teslas get about a lap and a half around Laguna Seca before the the batteries hit the max temperature and you lose most of the power to prevent them from overheating.

quick calculations:

A gallon of gasoline has about 129 MJ of energy.  Assuming ICE at 30% TE, That's about 40 MJ of energy converted into motion.  At a typical LeMons race, gasoline burn rate is about 4 to 5 gallons/ hr for a Miata or similar.  So figure about 200 MJ per hour.  

Assuming a EV is about 85% efficient, that would require approximately 235 MJ of storage per hour.  A Watt is 1 joule per second.  Roughly you're looking at 4 MJ per minute, and 0.0653 MJ/ second.  That's 65kW.  

So, assuming you could keep it cool, a 65kW pack should allow you to stay on track for an hour.  As stated, the top, winning teams are doing about 2 hour stints at a minimum.  Pit stops are let's say 5 minutes.  You need a battery swap setup that can hit the 5 minute bogie, and be good for ~130kW.  

The problem with more frequent stops is that often the pit road bypasses the timing strip on the track.  So you "lose" a lap when you come in for a pit stop.  Thus, if you have to pit twice, even if your stops were only 2 minutes long, you'd lose an extra lap, which is about 2 minutes or so at a typical track.  That puts you down a half lap, total, for every extra stop.  

In reply to volvoclearinghouse :

So a Tesla 85kwhr battery weighs 1200lb, if the interwebs are right.  

There is another factor to consider: The weather at a race. Ideally, you’d want a cool, but not cold event or a event that moderately warm. Ideally it would be a late spring or early fall one.

Get Lucky with the weather and that’ll help the cooling.

I think you would want cold.  Vehicle  range is compromised in the cold because 1) defrosters(s) 2) HVAC + seat heaters 3) battery temperature too low

1 and 2 you probably wont need.  3 is not an issue in a race environment.

I don't think the rules part of this has been fully investigated yet.  Doesn't CMP have a quiet hour on Sundays?  IIRC, the Electra team got to run during that while everyone was parked.  Would all EVs be eligible for this?  An extra hour of track time might close the performance gap.

Electrocet.  With fast swap battery under the floorboard.