Moroso Motorsports Park Dec 30, 2006

Session 1 Qualifying 9:50 AM

This is a fifteen minute qualifying session.

We need to get data on power consumption to decide what power level we can run for this afternoon's 31.5 mile race.

Based on our last time at Moroso, we expect to use around 775 Whrs per mile at 300 amps and 1075 Whrs per mile at 600 amps.

The pack has a total capacity of 35.150 kWhrs but without our BMS, to be safe, we will keep the charge between 20% and 90%. So we will only be able to use 70% of capacity which is 24.605 kWhrs.

Power level kWhrs per mile kWhrs needed for 31.5 mile race % of capacity available at this amp draw Worse case available kWhrs

We decide to qualify at 400 amps.

Since the BMS is not working, we decide to put the battery temperatures on the screen in front of the driver.


Race screen to allow driver to monitor battery temperature


The officials decide to combine the Spec racer group with our Production based classes. Spec racer is a class of purpose built race cars. They share identical chassis and motors. They are light and should be able to out accelerate and out brake us. Sharing the track with them is a little difficult since they are fairly low and hard to see.

Pesky  Spec Ford on left

On the out lap, a Production car flips over in the chicane. It rests upside down in the chicane. The track is black-flagged and we pull into the pits. We wait while they clear the track.

waiting on pit row
They send us out again.
Ready again?

My brakes are bad. The car does not want to stop. Part of the problem is the regenerative braking switch for the front wheels is in the 'Off' position but we will not figure that out till later. This means we only have 100 amps of regen through the rear wheels.

In the corners, the tires grip but quickly feel greasy. They are autocross tires and this is a long run for them.

My mirror keeps tilting up under braking. I must reach up and readjust it and check for Spec racers in every corner.

exiting the chicane

A 1:53 -my first lap.

I try too hard my second lap and go off in turn 9. A slow spin and then back in action.

The next lap is my fastest. 1:50.9s despite having to lift for traffic on the front straight-away.

View fast lap video (~21MB -.wmv file)
My next lap is 1 second slower and the session ends.


Using data from the rear motor, since it had it's regen turned on, we find that at 400 amps we seem to be using .946 kWhrs per mile. This is higher than we expect, but the car is carrying an extra 160 lbs of batteries and the maximum regen current is set lower than before. Which means we will need 29.799 kWhrs to complete the race at 400 amps. So we will only run 300 amps in the race.

Battery temperatures peak at around 49.5 C.


We put the car on charge at 11:45 a.m. The cells are all within .03 volts of each other. We set the Fluke meter on Cell # 50 and stop charge when it reaches 4.05. This happens after 2:05 hours of charging.

tracking one cell

The charger reaches thermal limit after an hour and a half of charging. So the crew uses a big fan to blow air into the trunk which helps cool the charger and allow more charging amps.


We change over to a treated set of road racing tires.

These tires are old but so far tires have not been the limiting factor.


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Final Prep Dec 30-31, 2006 Moroso
SARRC Race 1,  12/30/06


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