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Discussion Starter · #1 · (Edited)
Hi all,

Little background first.

I love drag racing and have a 1963 Chevy C10 the is powered by E85 drinking 418" LSX motor on 2 stages of N20. Its best pass to date is a 9.20 @ 144mph in the quarter. My engine in the C10 has been very reliable but after 8 years of beating on it, it needs a freshen up. I also have a friend interested in buying it. I weld, fabricate, I understand current flow and have a fairly sound understanding of electrical systems from years of working with EE's.

I work for a company that makes magnetic components for the high tech industry. We specialize in both power and signal magnetics. I work with a lot of companies that make battery packs, motor controllers, motors, high current chargers etc. I have a new job title and am now focused on EV.

With my new title at work, I am thinking I want to go EV. I think it would be awesome to talk to the engineers I work with about my EV drag truck.

I'd like it to be able to go 8.5x in the quarter and still street drive it like I do today.

The truck currently weighs 3120lbs with me in it. I figure I would be removing about 800lbs for all items used to propel it currently:
Fuel system
Engine
Trans
Radiator
12v deep cell battery
N20 system

Obviously weight will be put back in it, but at 3120lbs to go 9.20, dyno verified I make right at 850rwhp. I'm guessing I will need to make an honest 1000rwhp to go 8.50 in the quarter. Not sure if the truck will be lighter or heavier, but this might be a good place to start.

First thought was all wheel drive as some of the events I run are no prep races so traction is limited. If I went this route, I am thinking 2 motors up front, one for each wheel through a CV shaft. Perhaps a single Sevcon controller (or similar) could drive both? Then for the rear, do I go through my existing ford 9" rear with a dual motor set up? Not sure a single controller would be enough here. I don't mind changing the gear ratio in the rear.

Direct drive on the front would require a 2,000rpm motor to net +160mph. 28" tall tire.

My math tells me my current 3.90 gear coupled with a 30" tire and 7,000rpm would net me 160mph which should be just enough mph. 5,000rpm if I put a 2.73 gear in it.

I obviously need to keep the batteries light but have no idea what kind of storage I need. For street driving I am thinking to have only 1 motor on for light cruise so this may require splitting the front motors using 2 controllers. IE kill the rear and 1 front motor by a couple switches wired through a relay to turn a signal wire off to the contrioller(s). Isolating front and rear would also be good for the burn out box at the track.

Any thoughts on what size battery would be needed for say a 200 mile cruise?
What about motors?
What controllers are available?
I also want a rapid charger that can hit my 220v 30a generator at the track. 6kw continuous output.

I will be bugging many of my EE friends at various companies soon. But any thoughts are appreciated.
 

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Pay a visit to NEDRA.com and/or Facebook or their yahoo group discussion list. John Metric is their current president and member here under that username. Check out his posts. Some good data from some of the quickest passes. He also sells drag race batteries. See lonestarracing.com or something like that.

major
 

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Hi
a 200 mile range and an 8.5 in the 1/4 are not mutually compatible

You can have a light weight drag machine - or you can have 200 miles

If you can live with 50 miles then the 1/4 miles is doable - maybe have a pallet of batteries that goes on the bed when you need 200 miles
 

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Discussion Starter · #4 ·
Correct me if I am wrong but energy storage is the main issue. A 200mile range requires a lot of energy storage and I have to assume 8.5x in the quarter at 3100lbs requires a lot of energy storage as well. I can't yet speak to how much energy is needed for both but I'm also not planning to drive 200 miles then click off an 8.5x pass. They need to be thought of as two different scenerio.

Take the truck on light throttle cruises equalling 200 miles.

Tow to the track and click off 8.5x passes. How many, don't know. I have to assume I would be using my generator to top off the battery between rounds.

One customer of mine is working on a 50kwh battery for EV busses.

Another uses Sevcon gen 4 size 6 controllers in their EV.

I work with Tesla, Nio, Zero Motorcycles, Joby Aviation to name a few. Hoping to discuss some things with their EE's that I know.

I'm not afraid of putting a heavy battery in the truck. I figure I have 800-900lbs of EV drivetrain to net me back at my current 3100lb race weight.
 

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Hi
You would be surprised at how little your drag racing will take

Say 160 mph - 70 m/sec - and 1500Kg that is 3,700,000 Joules or just over 1kWh in kinetic energy

It will take more than that - but probably only about twice as much

You are using a LOT of power - but only for 8 seconds!

Run it the other way around 1000 rwhp - call it 1000 Kw electrical for 8.5 seconds = 2.36 kWh

But you won't be using your 1000 kW for the whole period - you will be using more power as the speed rises - so if 1000 kW is the peak power then the average power is more like 500 kW


But your 200 miles will be about 80 kWh - 40 times as much!

I'm nowhere near as fast as that but I do have over 500 Hp in my 900Kg "Device"
After a day with four 1/8th mile runs I have used up less than 10% of my 14 kWh battery
 

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You would be surprised at how little your drag racing will take

Say 160 mph - 70 m/sec - and 1500Kg that is 3,700,000 Joules or just over 1kWh in kinetic energy

It will take more than that - but probably only about twice as much

You are using a LOT of power - but only for 8 seconds!
This completely ignores the energy required to overcome rolling drag and aero drag; that might be a reasonable starting assumption.

Unfortunately, I don't think the overall efficiency (including the driven tires) will be anywhere near as high as 50% at this high power level.

But you won't be using your 1000 kW for the whole period - you will be using more power as the speed rises - so if 1000 kW is the peak power then the average power is more like 500 kW
If the truck really uses 2 kW-h (7.2 MJ) in 8 seconds, that's 900 kW... average.
 

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I'm nowhere near as fast as that but I do have over 500 Hp in my 900Kg "Device"
After a day with four 1/8th mile runs I have used up less than 10% of my 14 kWh battery
That's a good baseline.

Now double the mass, double the power, but more importantly double the drag distance for much more than double the energy consumption, and that's a lot more energy... but still less than would be needed for cruising the desired distance.
 

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First thought was all wheel drive as some of the events I run are no prep races so traction is limited. If I went this route, I am thinking 2 motors up front, one for each wheel through a CV shaft. Perhaps a single Sevcon controller (or similar) could drive both? Then for the rear, do I go through my existing ford 9" rear with a dual motor set up? Not sure a single controller would be enough here.
It sounds like the plan is for brushed DC motors. One controller may be able to drive both left and right front motors, but when one unloads more than the other (due to the truck's reaction to driveline torque to the rear) this sounds like an issue, as the unloaded tire loses traction and spins.

There are AC motor controllers which are intended to drive two mechanically separate motors on the same axle, which would be suitable for the front.

There is also the issue of coordinating the front and rear, so you're not spinning one end when traction is still available to drive harder at the other end.

For street driving I am thinking to have only 1 motor on for light cruise so this may require splitting the front motors using 2 controllers. IE kill the rear and 1 front motor by a couple switches wired through a relay to turn a signal wire off to the contrioller(s). Isolating front and rear would also be good for the burn out box at the track.
I understand the benefit of being able to switch front and rear off independently, but for street driving I don't see any benefit to switching anything off. Unless you use something like locking hubs, all the same mechanical parts will still be spinning, so there is no reduction in mechanical drag. Distributing drive force among fewer motors just means each takes more power.

I certainly wouldn't want to run only one of two front motors; the steering reaction would be unpleasant.
 

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Main issue for drag race is force / mass.

Main issue for range is energy stored / efficiency.
Taking that a step further, force multiplied by speed is power, which is the real issue for the battery when racing.

A bigger battery is better for both energy stored and peak power, but for a given size the battery deign which stores the most energy is not likely the battery design which can deliver the highest power.

Maybe one approach would be to design to handle the drag power (because drag performance is going to be sensitive to mass), and see how much range that provides... it might be enough.
 

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Taking that a step further, force multiplied by speed is power, which is the real issue for the battery when racing.
The real issue is force. Power is a consequence.

A bigger battery is better for both energy stored and peak power, but for a given size the battery deign which stores the most energy is not likely the battery design which can deliver the highest power.

Maybe one approach would be to design to handle the drag power (because drag performance is going to be sensitive to mass), and see how much range that provides... it might be enough.
The ideal battery (EESS, electric energy storage system, could be a capacitor) would be depleted or zero SoC, at 1321 feet. That way you carry no unnecessary mass down the track. There are batteries getting to, or near, 200C. That's an 18 second complete discharge. Even at lower discharge, or easy driving, I don't think he'll see 800 times the 1/4 mile range with an EESS capable of 8.5s in a truck.

Regards,

major
 

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The real issue is force. Power is a consequence.
How much power is needed is determined by the force required to accelerate the vehicle, the speed, the efficiency of the mechanical and electrical systems, etc. How that power demand is calculated is important, but in the end irrelevant to the battery.

The force applied to the vehicle, and even the resulting acceleration, are of no consequence to the battery - it must supply power. So calculate the power and put the rest of the dynamic data away for the remainder of the battery selection process.

The battery doesn't care if the power from it is accelerating the truck down the quarter mile or churning through a mud bog - it just delivers electrical power.
 

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I'm not highjacking (or hijacking) anything... my comments are entirely about sizing a battery for the desired drag race / street truck.

The linked thread was about the importance of one value out of context. It would be nonsense to consider only voltage or only current output capacity when sizing a battery; you need to consider the combination. You don't need to know what that power is being used for: you can put the 1,000 kW into a fast low-torque motor with lots of reduction gearing, a slow high-torque motor with taller gearing - or a really huge toaster if you want - the battery doesn't care.

For most EV builders, the capacity of the required battery is reasonably straightforward: estimate energy consumption per unit distance (e.g. 360 W-h/mile), multiply by range (e.g. 50 miles), and you have required capacity (24 kW-h). In this example, a salvaged Nissan Leaf pack (rearranged as appropriate to the desired operating voltage) would match nicely.

For a drag racer of this performance level, that approach might not work. Four passes might need only 8 kW-h, or one-third of that Leaf pack. A Leaf pack contains 48 modules in series, so a one-third pack could simply be 16 modules in series, nominally running at 120 volts (perhaps suitable for the motor). Although containing more energy than required for a couple of 1/4 mile passes, this set of 16 modules is designed to deliver up to 27 kW (225 amps at 120 volts) in the car for which they are designed... but you briefly need over 30 times that much power. Aside from the interconnections between cells probably behaving more like fuses than wires at 8,000 amps, can the cells themselves handle that, even for a few seconds? The Leaf cells are not the 800C rate type mentioned.

It seems inevitable that the battery size and design is going to be driven by the power requirement, and the configuration (how many cells in series and parallel) will be driven by matching the voltage and current requirements of the motor. If cells designed for very high discharge rate (compared to their capacity) are used and the system is sized just big enough for sufficient power, it might not be able to store enough energy for acceptable range.

To put things in perspective, we're talking about a power level which is higher than that of a Tesla Model S Performance model in Ludicrous mode. The Tesla can only get that power level from the battery for a short duration, the power is limited by the battery, and this is an enormous 90 kW-h or 100 kW-h battery.
 

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http://www.ampahaulic.com

Here's the link to John Metric's website. I had it wrong in post#2. Click on batteries there up top of the homepage.

You'll need something like the sleeper-cell or better to get a force/mass ratio to enable an 8.5.

Just my opinion.

major
 

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8.5 sec qtr is a serious performance vehicle, and i would suspect you dont want to compromise that potential on the track by hauling an extra few hundred pounds of unneccessary battery up the strip.
Consider a dedicated "race" pack (talk to J Metric) , and a bigger removeable "road" pack of suitable capacity for the trip, that can be left in the pits together with all the other gear that you dont keep in for runs.
Dont forget you are going to need chargers, generators etc , as well.
 

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I believe there is a way to get your 8.5s and 200 mile range pickup.

Step 1: Buy Tesla P100D
Step 2: cut everything off of Tesla until it is a bare chassis
Step 3: meticulously reproduce your 62' pickup body into a 1 piece carbon fiber shell that weighs no more than 100lbs - shaving all joints and smoothing corners so as to increase it's aero efficiency
Step 4: Bungee/Zip tie truck body to Tesla Chassis, run 8's
 

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I believe there is a way to get your 8.5s and 200 mile range pickup.

Step 1: Buy Tesla P100D
Step 2: cut everything off of Tesla until it is a bare chassis
Step 3: meticulously reproduce your 62' pickup body into a 1 piece carbon fiber shell that weighs no more than 100lbs - shaving all joints and smoothing corners so as to increase it's aero efficiency
Step 4: Bungee/Zip tie truck body to Tesla Chassis, run 8's
:D

But seriously, the Tesla structure is a unibody, so if you cut the roof off it isn't a driveable vehicle - the often-shown "skateboard" is just a collection of parts which can't hold up a load (the battery case has strength, but is not the frame). An 8.5-second drag truck requires a roll cage anyway, so Step 2 would need to be:
  • "build a truck-shaped tube frame and move all of the Telsa parts to it"
With any luck, that would save enough weight to bring the P100D quarter mile down enough from 10.44 @ 124.21 mph. Of course, one could forget the truck and just race the Model S, but even stripping the interior and replacing some panels with lighter composites doesn't look like it will make that light enough.

I think more-than-P100D power will be needed for the 8-second truck, but maybe just keeping the mass down will do it. Aero is a challenge, though...
 

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Discussion Starter · #20 ·
In all fairness and no disrespect meacted here, but those of you that talking about cutting things up, concerned about the possibility of 200lbs additional in battery weight; how many of you have built a 10 second vehicle regardless of how it is powered? Now, how many of you have built something from the ground up that runs consistent 9.2x at 3,120lbs with the aerodynamics of a billboard wearing a construction hat? I have, not EV, but I get the weight/power needed to do it.

200lbs is +/- 0.2

Again, I have 800-900lbs to take out with the current ICE set up. If I added that amount back in, I would need to make an equivalent 800ftbs/1000rwhp. But, I am banking on a higher tq output and less hp could do it too. Explosive energy to the 330' makes up for lack of MPH in the 1/4.

My mph for 9.20 is considered off or slow. But that is because I focused on 60'


My goal may be lofty, but instead of picking it apart, let's figure out what needs to be done to make it happen...


For those of you that have provided positive and real input (you know who you are) THANK YOU.
 
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