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rich911s
rich911s New Reader
11/26/22 9:42 p.m.

Ever since Michael schooled everyone at the 2022 $2000 Challenge in his Tesla model 3 performance (best dynamic score overall) I've been dreaming of putting an EV drivetrain in a challenge car.  It's gotten so bad that I have a way too long list of Copart searches saved to my dashboard.  I've been seeing quite a few EV's come across the auction block... some well within striking distance of a $2,000 challenge price.  Mostly older totaled or flood damaged cars.  Forgive my stream of consciousness here, but I have several questions about a potential EV challenge car if anyone cares to take a gander and chime in:

1.  First and foremost, I'm sure there are many people across the globe wanting to do something like this.  Does anyone know if there is an open source motor controller for AC EV motors?  Is someone working on one? I know AEM came out with a very expensive option (Like $5K), but I'm looking more for the Megasquirt/Speeduino type DIY approach that would make it challenge friendly. 

2.  Forget those big heavy battery packs!  For challenge purposes, we don't need no stinkin 2,000lb pack!  Why couldn't we break down the big packs into smaller 200lbish? packs that can be hot swapped after a few runs.  Range doesn't matter for the challenge.  I know flood cars will have all sorts of electrical gremlins and older cars will have run down packs, but a lot of those cells should still be viable.  Just need to test and re-configure them into smaller units is what I imagine. 

3.  Recharging?  We would need a big generator to recharge packs while trackside.  Kinda defeats the whole green thing, but we're going for gold, not green!  I have access to a towable diesel generator that puts out 30KW.

4.  I think That's it!  Seriously, what else do you think would be needed to make it happen?  For real, it's an  electric motor, plus to plus goes forward, reverse polarity to go in reverse.        

5.  Wait... maybe a 2-speed tranny for the drags? 

ProDarwin
ProDarwin MegaDork
11/26/22 9:54 p.m.

For #2, a smaller pack would have to be totally rebuilt to still output at the same power level as a larger one.  It's not just range, it's power output which has thermal and wiring/conductor/etc limitations.

This is why usually the most powerful of any given model is also the one with the longest range.  It's not a motor restriction it's the battery pack.

rich911s
rich911s New Reader
11/27/22 9:13 a.m.

In reply to ProDarwin :

I agree.  There are about 6-7,000 cells in each battery pack broken up into approximately 16 modules depending on the model and range.  

singleslammer
singleslammer GRM+ Memberand PowerDork
11/27/22 11:50 a.m.

If you can do this under budget, you will be a legend. 

GIRTHQUAKE
GIRTHQUAKE SuperDork
11/27/22 12:08 p.m.

In reply to rich911s :

1. Open Inverter Wikia. They've unlocked all years of the Prius so far, which would allow motor power just under 100Kw (aka ~220hp). There's also the Axiom project, which is an open source inverter up to 100Kw for brushless DC motors.

2. I echo what prodarwin said. There's a chance that in breaking down damaged packs and selling good ones, that you could come into budget running a high current, high voltage but low range pack.

3. Depends on how much power you've got on board, and how fast you wanna charge it and if you even have one aboard for weight savings. Some inverters have built-in chargers like Teslas, so that's a big "It depends" question. Some tracks supposedly have NEMA 14-50s as well.

4. Well, locally to me a while ago I could have bought a Nissan Leaf pack that was at 55% life for a grand. Schools also semi-regularly have EV projects that they decide to dump, and guys like Rich have snagged serious used hardware for next to nothing before. I think it'll be a VERY custom affair, but I can find my links for EV classifieds for you.

I believe... that the cheapest route based on what I've seen, is either a wrecked leaf bought a copart with a Lebowski brain to unlock the controller (with the rest of the car converted into something like an EV Hot rod) OR a leaf pack driving that hacked Prius inverter with the largest 3-phase AC motor you can find. No idea what you'd do for a body or wheels; you'd REALLY want a diff that works with the high speeds AC motors can achieve, and most EVs are like 8:1 all the way up to 12:1 for differential gearings (!). Brushed DC are slower and can use stock gearings, but you really don't want them.

5. Could work, but you'd lose regen and you'd want that for autocross crying

GameboyRMH
GameboyRMH GRM+ Memberand MegaDork
11/27/22 12:39 p.m.

For #2, you could change the series/parallel arrangement of the modules in the pack and do a few mods to the battery pack harness to get a smaller/lighter pack with the same voltage. The issues would then be working out control electronics (the "ECU" will throw a fit at a pack with the wrong number of modules in it) and making sure your smaller pack can still output enough power for the motor/inverter (and without overheating). I don't think lightweight quick-swappable packs would be doable, you'll probably need at least 500lb packs to get a decent amount of power out of the type of EV batteries available in junkyards even for the length of an autocross run.

Maybe the answer would be to lighten the rest of the car - a Leaf ghettocet should be competitive with a lot of hot hatches, but that's still not close to a Tesla 3P. Maybe a dual-powertrain Leaf ghettocet running from one pack's worth of batteries?

Edit: A Leaf's battery pack is about 650lbs, which is pretty minimal already (not surprising considering the Leaf's specs). If a Leaf ghettocet can be built at 1500~2000lbs minus batteries, adding 1300lbs of batteries wouldn't be so terrible...

malibuguy
malibuguy GRM+ Memberand HalfDork
11/27/22 12:48 p.m.

I have been thinking of doing an EV conversion on my 4dr tercel, more to learn and see how it can be.  But its just too cost prohibitive for me to even remotely experiment with.  If I was more techy? I could probably find ways to do it cheap but more or less I am a completely ignorant to EV stuff.

I do not even need anything major, gimmie 100hp and like 150miles of range Id be happy

SV reX
SV reX MegaDork
11/27/22 1:03 p.m.

Paging Mr Joshua...

sleepyhead the buffalo
sleepyhead the buffalo GRM+ Memberand PowerDork
11/27/22 1:03 p.m.

I thought I remember someone saying that Ford C-Max batteries were the real bargain in second-hand Lithium packs, back in ~2019 or 2020?

I agree that a Leaf is probably the place to start, especially if you unlock its inverter, and increase the motor's output from 80kW up to 140-ish kW.

If I were to attempt this, I'd try to keep it a small-ish single-motor setup, and then have a setup of tires for the autocross that are smaller than the OEM Leaf 25.5in tire, and then swap on some stickier drag tire that's over 25.5in diameter.  Maybe.  You'd want to see what RPM you can reach with the 140kW "tune"... and decide if you need a taller tire to not over-rev by the end of the course (Vmax on the Leaf motor, stock tire, stock differential is somewhere between 90-93mph)

SV reX
SV reX MegaDork
11/27/22 1:06 p.m.

Regarding hot swapping battery packs...

 

Its been discussed.  All the batteries used would need to be in the budget.  

I think it comes down to being wild-ass lucky on your purchase prices on about a dozen separate component purchases. 

MrJoshua
MrJoshua UltimaDork
11/27/22 1:18 p.m.

Off the top of my head and from memory so estimates that may not be perfect:

-openinverter forum zombieverter, or control boards on the factory inverter of choice. )The openinverter forum info is biased towards Toyota stuff.)

-Leaf motor has been pushed to 300whp. Toyota Hybrid transmissions have been used as drivetrains, but most of the conversion people have not been hi HP biased so true potential isn't well verified. They may/may not only get high HP with really really high voltage.

 -$800 Ford Cmax energi battery can do 150kw. $1k Volt battery can to 250kw.

-It's doable under $2k with good shopping. I have the parts to do it in at least 3 different ways and know of at least 2 more.

Message me and I will talk your ear off about the many different possibilities. 

Keith Tanner
Keith Tanner GRM+ Memberand MegaDork
11/27/22 1:24 p.m.

One thing to know about batteries - their maximum power delivery is a function of their capacity. If you take a 2000 lb battery and throw away all but 10% of it, you'll also find you can only deliver 10% of the maximum power. Having a Leaf motor pushed to 300 hp doesn't do you any good if your little battery pack can only deliver 30 hp worth of electricity.

The whole "let's just use a small battery" concept comes up fairly often, but it's not the same thing as a small fuel tank. Think of each cell as a little gas tank with its own fuel pump if it helps, and if you take away fuel pumps you can't deliver as much fuel.

03Panther
03Panther PowerDork
11/27/22 1:45 p.m.

In reply to Keith Tanner :

Your tiny fuel pump analogy is one of the best layman's term analogies I've seen!

But anyone that doesn't get that needs to do some science research, instead of media info. 
 

(Some folks know this, but mention voltage, forgetting that others don't:)
Voltage gets mentioned a lot: voltage (measured in Volts, ie. "V) is NOT Power (measured in Watts, ie. P)

Higher voltages do NOT inherently give one more power. 
Voltage and Current (measured in Amps, ie. "I") are inversely related to Power, but there is A LOT more too it than higher voltage packs. 
Remember, Lunnie's , T. I. N. S. T. A. A. F. L

(The Moon is a Harsh Mistress: there is no such thing as a free lunch)

AAZCD-Jon (Forum Supporter)
AAZCD-Jon (Forum Supporter) SuperDork
11/27/22 1:58 p.m.

Thinking of energy storage and discharge... How about augmenting fewer batteries with a large bank of capacitors? Program a controller for how many to dump on demand/sequentially. Less weight than the batteries, but high potential for short bursts of wattage.  ??

MrJoshua
MrJoshua UltimaDork
11/27/22 2:51 p.m.
AAZCD-Jon (Forum Supporter) said:

Thinking of energy storage and discharge... How about augmenting fewer batteries with a large bank of capacitors? Program a controller for how many to dump on demand/sequentially. Less weight than the batteries, but high potential for short bursts of wattage.  ??

Capacitors are not very energy dense so you end up with a LOT of weight for the power available. The ability to dump energy quickly isn't as big of an issue as it was in the past. Modern batteries dump energy fairly quickly, and as Keith referenced above having a larger capacity pack allows for higher peak power as well. Often the stock motor and inverter are capable of delivering more power than the EV is rated for, but for best battery longevity with the size pack the vehicle is delivered with the total system power is limited. 

If you want really high power and low weight batteries you look to the EV drag race world. They are using low capacity/high discharge cells that are really really power dense. A 600hp pack can be built to around 100lbs. They are intolerant of neglect and have a low cycle lifespan, but wow they are powerful.

nocones
nocones GRM+ Memberand PowerDork
11/27/22 2:54 p.m.

In reply to MrJoshua :

I am very interested in the idea of a GRM electric conversion for the Autobianchi for challenge budget.  I need to verify that I can get a title for it, but if that can be achieved Electric is my #1 desire for a drivetrain.   I would be very interested in learning more.  I can do the fabrication parts, but the electrons are foreign and scary to me.  I will PM you when I get closer to getting that project going.  

Robbie (Forum Supporter)
Robbie (Forum Supporter) GRM+ Memberand MegaDork
11/27/22 4:10 p.m.

Uuuuhhhhmmmmm, link to copart sales of evs that go for less than 2k? 

I was looking before pandemic used-car-flation and couldn't even find wrecked leafs less than $2k.

I have the rest of a car ready to go if I could find the donor leaf!

MrJoshua
MrJoshua UltimaDork
11/27/22 4:52 p.m.
Robbie (Forum Supporter) said:

Uuuuhhhhmmmmm, link to copart sales of evs that go for less than 2k? 

I was looking before pandemic used-car-flation and couldn't even find wrecked leafs less than $2k.

I have the rest of a car ready to go if I could find the donor leaf!

Looks like a lot of GEM cars might go under $2k. laugh

AAZCD-Jon (Forum Supporter)
AAZCD-Jon (Forum Supporter) SuperDork
11/27/22 4:54 p.m.

I know of a few dealership repairs around here where new parts were put on and old, but still 'Challenge-worthy' parts were disposed of. TDI Touareg EGR parts replaced rather than cleaned, One wheel scraped in a collision, style is NLA, car gets four new and the old ones are trash. Can you get 'bad' battery packs or other salvable EV parts from a Toyota/Nissan/...  dealership? Curb alert from the service department?  I got a 475lb patient lift that needed new batteries - alerted from Bio-Med that they were throwing it out as condemned. Later got  a couple racks of 12V batteries and  commercial UPSs. Not a special deal other than knowing they were being disposed of.

GIRTHQUAKE
GIRTHQUAKE SuperDork
11/27/22 5:07 p.m.

 Nissan Leaf motors/inverters have been taken to 300HP stably but no further. 

This Ford pack out of a Fusion (?) hybrid is $100 flat. Greentec auto had C-max batteries, A 24 Amp-hour pack for $430 and a 5.5 Amp hour pack for $275. Problem always seems to be, getting a decent deal at a good time and if they still have their BMS attached.

MrJoshua said:

Message me and I will talk your ear off about the many different possibilities. 

I want to hear them.

rich911s
rich911s New Reader
11/27/22 6:43 p.m.

In reply to Robbie (Forum Supporter) :

They're out there for sure.  Here's one that runs and drives with a buy it now price of $2,250. Probably going to go for under $1500.  

rich911s
rich911s New Reader
11/27/22 6:46 p.m.

In reply to GIRTHQUAKE :

So, (2) motors would make... 600WHP? 

rich911s
rich911s New Reader
11/27/22 6:49 p.m.

In reply to GIRTHQUAKE :

OH YEAH!  That was exactly the link I was looking for, Thank you!  

GIRTHQUAKE
GIRTHQUAKE SuperDork
11/27/22 6:55 p.m.
rich911s said:

In reply to GIRTHQUAKE :

So, (2) motors would make... 600WHP? 

Yes! And because the pedal is just a potentiometer, you can just send the signal to both motors!

rich911s
rich911s New Reader
11/27/22 7:25 p.m.

In reply to Robbie (Forum Supporter) :

Just an FYI, as of right now there are 9,267 EV's or Hybrids listed on Copart!   All of them have some kind of electric motor and battery pack in them.  There are certainly a plethora of deals to be had, just have to figure out the best course of action for the least amount of $$$ to make it happen.   

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