# 2011 Sandhills Open Road Challenge in an EV



## DIYguy (Sep 18, 2008)

Brute Force said:


> Not as exciting as a 200MPH blast at Bonneville, but here's my in car video at the Half Mile Shootout:
> 
> http://www.youtube.com/watch?v=VzHWJgFOe78
> 
> ...


Nice job on the dual motor drive. You need a real battery.  Honestly, and I'm not criticizing, but I think you could have done about the same thing with one Soliton controller and a better battery. Once you get some lithium in that thing..., it will scream. . . more like 11 seconds than 15 or 16.  Nice job though... it's a whole lot more work than a conversion, that's for sure. 
What's ur motor rpm at the top speed? Looks like ur running out of rpm...??


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## Brute Force (Aug 28, 2010)

I had two issues at the Shootout. The first was traction. The tires are old and hard (this project has dragged on WAY too long). Watch the launch, I couldn't give it the full 1000 amps without smoking tires. A fresh set of stickies will go a long way towards cutting the ET.

The second issue has yet to be diagnosed, the system acts like it is rev limited. It accelerates hard up to 80 MPH then hits one of the programmable limits in the controllers (SWAG: motor voltage limit). Since I didn't have a laptop mounted I don't have a datalog of the event. I do know that 80 MPH is 4300 RPM. Some time on a chassis dyno is needed to sort out the fiddly bits.

One controller won't do the same job. With one controller I have to choose between half the current to each motor or half the voltage.

I agree that I need a set of lithium batteries. They're on the slate for next season. The Optima yellow tops worked well at the shootout, they were not the limiting factor in this particular instance. The road race was a different story. Capacity left me sitting at the side of the road.


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## Bowser330 (Jun 15, 2008)

so the video says 21 yellowtop 12V batteries so that means 252V...right?

So im assuming because they CCA = 750A, your dual solitons are connected in series to the battery pack and are sharing the packs 252V, so, only 126V each.


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## Brute Force (Aug 28, 2010)

The batteries are all in series. Fresh off the charger the pack voltage is 275 volts. The Solitons each get the full pack voltage. I'm sure the voltage sags considerably under load.


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## Bowser330 (Jun 15, 2008)

Brute Force said:


> The batteries are all in series. Fresh off the charger the pack voltage is 275 volts. The Solitons each get the full pack voltage. I'm sure the voltage sags considerably under load.


What do you have the soliton's set for motor voltage? 

Since the yellow top D34's are rated at 750 CCA & 870A when warmed up...i agree that your voltage is sagging considerably when drawing 1000A from the pack...(500A for each Soliton & Motor)

So if each motor is only getting 500A, and if you have the motor voltage limit set at 150V then that is only 75kw for each motor...also 500A in a warp9 motor is only about 110ftlbs of torque so...

Total hp/tq output:
200hp
220ftlbs 

If you are to upgrade to lithium, you can build a pack that can output 2000A and provide the full 1000A to each warp9, doing so would increase your torque to 277ftlbs each (554ftlbs total)

according to data from jack r., the warp9 @ 1000A produced 156hp @ 3200rpm

So with Lithium..
312hp @ 3200rpm
554ftlbs


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## Brute Force (Aug 28, 2010)

Motor voltage limit is set at 150 volts.

You're equating motor current and battery current, which is incorrect. It's the motor and battery wattage that are equal (approximately).

From a dead stop up to around 40 MPH the system is running in the current (torque) limited region, and the controllers will put a full 1000 Amps into each motor. After that the system is operating in the watt (horse power) limited region and the controllers back off the current to maintain a constant 75KW. I LOVE these Solitons!

My choice of limits were conservative to reduce my chances of a (another) spectacular failure, both motor and battery. I really wanted to get to the road race this year, which I did.

The lithium battery packs are already on the drawing board. They'll drop my gross weight by 600 lbs, triple my kWh capacity, and double the useful amps.

As you pointed out, it is all about power.


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## Bowser330 (Jun 15, 2008)

Brute Force said:


> Motor voltage limit is set at 150 volts.
> 
> You're equating motor current and battery current, which is incorrect. It's the motor and battery wattage that are equal (approximately).
> 
> ...


you are correct, my mistake.

so you ARE getting 554 ftlbs of torque from 0-40mph, wow that must feel like a being shot out of a cannon.

Do you have the time slips of your 1/4 mile runs? I would be interested in seeing the 1/8th mile time...


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## Brute Force (Aug 28, 2010)

Haven't been to a drag track, so I don't have any time slips. Just a semi-official quarter mile ET and speed from the SORC shootout.

Traction is killing my launches. I have 2000 lbs of trust where the tires meet the pavement and some old dried out tires. It's a delicate art to hold the throttle just where the tires don't quite spin. I need new tires and more practice.


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## Bowser330 (Jun 15, 2008)

Brute Force said:


> Haven't been to a drag track, so I don't have any time slips. Just a semi-official quarter mile ET and speed from the SORC shootout.
> 
> Traction is killing my launches. I have 2000 lbs of trust where the tires meet the pavement and some old dried out tires. It's a delicate art to hold the throttle just where the tires don't quite spin. I need new tires and more practice.


Have you tried adjusting the slew rate and throttle ramp-up parameters in the Soliton1's?

Essentially you can program the controller to slow the ramp-up of the motor amperage requested by the throttle. This can help with:
(1) Less shock/stress on other driveline components
(2) Less unintentional burn-outs mean less tire wear
(3) Sticking during launch!, less wheel spin and wasted energy


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## Brute Force (Aug 28, 2010)

I've played with the current ramp rate and have it set at 10,000 amps per second. Sounds like a lot, but the throttle is crisp without being harsh. Slower rates felt mushy, like there's a big rubberband between the powertrain and the rest of the car.

And the tires still spun when the power finally caught up.


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## Brute Force (Aug 28, 2010)

Did I mention that Optima Battery is an SORC sponsor? They brought a Speed Channel camera crew to cover the event and took an interest in my EV. There will probably have some of me (gack!) and my monstrosity on an upcoming Hot Rod TV episode


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