Roebling Road Test Day - 4/27/07

Session 2, 10:45 AM

 
The pack is close to fully charged, reading 384 volts.
 
I go out and immediately turn a 1:26. The track is dry and I have had some time to think about how to drive it.
 

I run 12 timed laps (14 total) at 400 amps.

There is some traffic, but I run 4 clean laps at 1:26.1 - 1:26.2.

Battery temperatures go from 39.6 C to 52.0 C.

We have used 23.293 kW-hrs.

 

The pack must be 45 degree Celsius before we can begin to charge. We place a fan in the front airbox and blow air through the battery boxes.

At 11:48 a.m., we put the car on charge.

 

We are using 824 watts-hrs per mile.

Therefore, we will need 28.288 kW-hrs for the race, plus power for a pace lap and a cool down lap, at 250 Watts-hrs per mile.
All together, 29.298 kW-hrs.

 

Fully charged, the pack should be able to supply 35.150 kW-hrs at a 1C rate of discharge.

This means, if we ran the car at a constant 100 amps, we would be able to use 100% of the 35.150 kW-hrs (see Puerkets equation for more information).

 

Looking at Kokam's Discharge Characteristics graph on the center of page 14, it shows that at 4C (400 amps) we should be able to use around 87% of 35.150 kW-hrs or 30.580 kW-hrs.

It sounds like 400 amps will use almost all our power, but we should be able to finish.

 
We decide to turn the power up to 450 amps to get a Watts per mile figure just to see if we can run a little more power.
 

Our race engineer, James Lee and I discuss the car's handling.

The balance of the car has changed since our last race at West Palm Beach. Now that we have brakes that work and improved tire grip, the car is reacting differently.
 

The higher g-forces are causing more weight transfer. The car is not turning in well and is understeering mid-phase.

To compensate, I am pitching the car sideways under braking and then letting the car understeer around the corner.

 
This is not optimal.
 
debriefing
 
We decide to soften the front sway bar and the bump on the front shock to try and increase front grip.
 
 


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