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John Webber
John Webber
7/11/18 12:54 p.m.


This story is from an older issue of Grassroots Motorsports.. Like stories like this? You’ll see every article as soon as it's published by reading the print edition of Grassroots Motorsports. Subscribe now.

Gas prices hit the $4 mark for the first time a few years back. That’s also when Ken Watkins had an epiphany while languishing in traffic: Day after day, month after month, he sat behind the wheel stew-ing while his Corvette burned gallons of the precious stuff. Finally he reached his limit.

But since Ken is a mild-mannered guy, he didn’t make like the deranged TV anchor in the movie “Network” and hang out the window screaming, “I’m mad as hell, and I’m not gonna take this anymore!”

Instead, he kept his mouth shut and built an electric vehicle.

First, he bought a theft-recovery Chevy S-10 and converted the little pickup to electric power. He enjoyed the project and learned a lot.

He drove the truck every day, relishing the attention it drew and pocketing the gas savings. Two years later, someone took a shine to the vehicle and made Ken an offer he couldn’t refuse.

Ken parted with the S-10 but was determined to build another EV, this one sportier and more fun to drive. Like a Corvette, maybe, only smaller and quieter.

Read the rest of the story

te72
te72 Reader
7/11/18 9:59 p.m.

I wouldn't mind trying the lithium ion version, if his math of 1/10 the weight is ballpark accurate. Figure 1700 lb Miata with instant torque? Now that... that could be fun. However, the "10x the cost" part would be rough. Figure a typical battery is $100, and there's 19 of the things in this car? So, by that (likely outdated, thanks technological progress and economy of scale!) math, we're talking around $19k just in batteries? Sheesh...

 

All in all though, it makes me wonder where the cost per mile math ends up on something like this. Driving experience on paper sounds horrible, but only because weight is the enemy of the Miata chassis. The less of it you have, the better it is, and vice versa. Figure the cost of energy, gas or electron, plus you wouldn't have to ever change the oil, filters, etc, BUT... you have to change the batteries around the 5 year mark.

 

I dunno why, but the math aspect of this is more exciting to me than the driving aspect.

exST165
exST165 Reader
7/13/18 2:56 p.m.

What if the goal was to build an autocross weapon?  Just enough battery for a 60 second run and power to rival a supercharged CSP?  There would be some gain from not having to shift if you could launch in second or third.  Could the batteries be small and light enough to not hurt handling?  For a 50 or 60 second run how much time is at WOT?  

Given the differences in torque curves what kind of electric motor would be needed?

GIRTHQUAKE
GIRTHQUAKE Reader
7/13/18 5:01 p.m.
exST165 said:

What if the goal was to build an autocross weapon?  Just enough battery for a 60 second run and power to rival a supercharged CSP?  There would be some gain from not having to shift if you could launch in second or third.  Could the batteries be small and light enough to not hurt handling?  For a 50 or 60 second run how much time is at WOT?  

Given the differences in torque curves what kind of electric motor would be needed?

Team Frozen Nuts Racing

It should be noted this article was made in 2013, and the advancements in battery technology since then have honestly been legion in number- Lithium-Sulfur and Solid-state seem to be the next types of energy storage we will see, though Lithium-ion will be hanging around for far longer. And thanks to the Leaf, Volt, and other EVs battery prices are falling quickly.

As for a motor? Depends honestly on price and maintenence. D/C wound motors are cheaper and have some interesting abilities over A/C due to brushing and affects of how they generate the field, but for preformance an A/C motor is what you want since they 'convert' electrical power to rotation faster. The other problem (in cost) is your controller- all batteries can do A/C power no problem, but the controller that takes consistent battery power and coverts to A/C will be expensive.

Since you don't need a transmission with motors (in some cases) an easy upgrade to this car would be two smaller D/C motors linked (somthing like a WARP9, since you can buy them with a diff-yoke pre-welded to the output shaft) for high torque, a limited slip diff for safety, and a controller than can handle sudden discharge but doesn't require any regen braking stuff. From there, you'd need to source a battery system, a vacuum pump for your brakes, a charger, and your gauges- lots of electric guys use crank position sensors on the main motor shafts for Speedos and there are plenty of voltimeters for EVs now that show charge in easy-to-read precentages.

SVreX
SVreX MegaDork
7/13/18 5:21 p.m.

I really want to do this!

SVreX
SVreX MegaDork
7/13/18 5:24 p.m.

With Leaf prices dropping through the floor, wouldn’t a wrecked Leaf be an excellent candidate for a drivetrain donor for an electric Miata?

Regarding the Autocross weapon... I considered this for the Challenge.  The car only needs to run for 60 seconds at a time. Spare fully charged batteries could be on site, Ready to swap in. Since they are not on the car, the spare batteries should be budget neutral. 

Justjim75
Justjim75 Reader
7/13/18 5:25 p.m.

In reply to te72 :

Not trying to be a butthead but it may help or hurt someone's decision to know, 19 batteries times $100 each is $1900, not $19k

kb58
kb58 SuperDork
7/13/18 5:42 p.m.

^ beat me to it...

GIRTHQUAKE
GIRTHQUAKE Reader
7/13/18 5:42 p.m.
SVreX said:

With Leaf prices dropping through the floor, wouldn’t a wrecked Leaf be an excellent candidate for a drivetrain donor for an electric Miata?

Regarding the Autocross weapon... I considered this for the Challenge.  The car only needs to run for 60 seconds at a time. Spare fully charged batteries could be on site, Ready to swap in. Since they are not on the car, the spare batteries should be budget neutral. 

Orange is the new Flat Black

Yes. Leaf batteries are about 4.3 amp/hours each. The stock motor for a leaf is somewhere in the 150 horsepower range with about ~200 'torque', but with aftermarket controllers and battery maintenence you could get more. Your main problem would be keeping them properly cooled.

kb58
kb58 SuperDork
7/13/18 5:51 p.m.

True, but being run hard for only 60-seconds, then being switched out, it seems like the thermal mass alone would keep it from getting too warm.

SVreX
SVreX MegaDork
7/13/18 5:54 p.m.

In reply to kb58 :

As a Challenge weapon, I’d run lead acids. Because they’re cheap. 

The Leaf battery would be better for a full time commuter. 

kb58
kb58 SuperDork
7/13/18 6:47 p.m.

I never decided whether I liked the semi-reality show "Fastest Car", but there was a Datsun 1200 in there that had been converted to electric. I won't give away the ending but it certainly had the power/torque to win... whether it did or not, you'll have to watch :P

(If you want to cheat and save some time, you can just jump to the last episode where they have their overly-dramatic run-off.)

SVreX
SVreX MegaDork
7/13/18 9:23 p.m.

In reply to kb58 :

That would be The White Zombie. It was built nearly 20 years ago, but now runs over $100,000 batteries which are Navy prototypes. It’s allegedly the worlds fastest electric car.

It may be wearing the skin of a 1200, but it is a very serious drag race car. 

exST165
exST165 Reader
7/13/18 9:31 p.m.

Just found a Warp11 on eBay for $3,900 so not Challenge material but 400 ft:lbs at zero rpm and goes to 4500 rpm weighs 226 lbs!  didn’t see a diameter but get a diff yoke adapter and mount it in the transmission tunnel straight to the diff.  Math would be needed to double check that it won’t run out of rpm at autocross top speed and probably some massaging of the tunnel.  Mount the batteries in the passenger seat area and the polar moment of inertia would be minimal!  But would that 226 lb motor and batteries be lighter than the Miata engine and transmission?  And to be fair supercharger.

Dream is to do something like this for Challenge money but until electric motors start appearing in junk yards in some volume I don’t see it happening.

te72
te72 Reader
7/14/18 12:40 a.m.
Justjim75 said:

In reply to te72 :

Not trying to be a butthead but it may help or hurt someone's decision to know, 19 batteries times $100 each is $1900, not $19k

Perhaps my explanation wasn't clear, or maybe it didn't read well. I was saying the lithium version was of interest to me. The article states that the builder of this Miata wanted to do a lithium powered version, due to them being about 1/10 the weight for the same power, but at a cost of 10x as much.

 

Typical lead acid battery, around $100. 10x that much for a lithium would be $1000 per battery. This Miata has 19 batteries. Hopefully that makes more sense. =)

DrBoost
DrBoost MegaDork
7/14/18 1:49 a.m.

$8,000 buys a LOT of gas. But I agree, it's cool and something I've always wanted to do 

BirgerBuilder
BirgerBuilder New Reader
7/14/18 9:01 a.m.

Chevy Volt Batteries have a similar range to this, 40 miles before you start dipping low enough to damage the cells. On ebay they currently go for... $2500. 

Get building guys. 

te72
te72 Reader
7/16/18 10:17 p.m.
DrBoost said:

$8,000 buys a LOT of gas. But I agree, it's cool and something I've always wanted to do 

One of my best friends just bought a used Tesla Model S. Cool car, but given what he paid for it, I think I could have Lexus rebuild my LS400 a couple times and still have money left over for 10 years worth of gas.

MrJoshua
MrJoshua UltimaDork
7/16/18 11:32 p.m.

In reply to GIRTHQUAKE :

80KW. Good torque, but they only hold it to 3k rpm.

Stampie
Stampie UltraDork
7/17/18 7:24 a.m.

In reply to SVreX :

You'd have to include all the batteries since they are used on course.  Real world example last year we caught our lithium ion battery on fire and replaced it with a lead battery during autocross.  We were told to include both batteries in our budget. 

SVreX
SVreX MegaDork
7/17/18 7:45 a.m.

In reply to Stampie :

I disagree.  That’s like saying you have to include fuel in a gas can, a spare turbo, or any spare parts (equal swap). 

I don’t doubt you had that experience, but I would seriously question it in terms of the rules.  The only thing required to be in the budget is what’s on the car when on course.  If your car has a radio and you remove it for the event, it’s not in the budget. Similarly, if it has more batteries than are needed to run the course, they are just spares.

The ONLY thing spare batteries would be would be to facilitate the event’s time requirements. They are avoiding recharge time, nothing more. 

I would certainly get staff approval first, but what you are suggesting makes no sense.

SVreX
SVreX MegaDork
7/17/18 8:01 a.m.

In reply to Stampie :

Perhaps neither of our examples were good...

The “Stampie Rule” refers to a breakdown. The builder choice to use parts that did not make it through the event does not give us a pass to use a better part for no budget hit. 

I’m not describing a failure. I’m describing a plan.  To bring a vehicle with only enough “fuel” to complete the course, then “refuel”. 

Perhaps a better example would be a spare nitrous tank. The budget must include a tank, but a spare tank just represents the ability to have extra nitrous available, since the drags are at night and additional nitrous is not available. 

Stampie
Stampie UltraDork
7/17/18 8:28 a.m.

In reply to SVreX :

I respectfully disagree. The battery is the "tank" the electricity you use to fill it is the fuel and I would include the spare tank cost but not the cost of the fuel. 

SVreX
SVreX MegaDork
7/17/18 8:35 a.m.

In reply to Stampie :

As I noted, I’d seek staff approval first. 

Right now, it’s just part of that “hypothetical E36 M3pile” (as a wise man once said)

mad_machine
mad_machine MegaDork
7/17/18 9:34 a.m.
GIRTHQUAKE said:

Since you don't need a transmission with motors (in some cases) an easy upgrade to this car would be two smaller D/C motors linked (somthing like a WARP9, since you can buy them with a diff-yoke pre-welded to the output shaft) for high torque, a limited slip diff for safety, and a controller than can handle sudden discharge but doesn't require any regen braking stuff.

I think I would want a 2 speed transmission. Even if it was something I had to stop to shift. A Low speed for around town and a higher Overdrive for highway use.

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