| The
tow truck brings us back to the pits. We pull the driver's seat and
the cover over the controllers. As we start to trace the wiring, the
cause of the problem becomes evident. The main connector to one of
the controllers is wet. |
| |
| Our
'slight' coolant leak must have gotten worse over test day. We refilled
the radiator last night and enough coolant must have leaked out to
form a small puddle. When I accelerated onto the track, the puddle
rolled back into the connector. This shorted the throttle signal.
The Siemens controller recognized that the voltage reading was above
the value set as full on (3.8 volts) and shut down the system. |
| |
| We
seal the small leak and disassemble and dry the connector. |
| The
computer reports all system 'Go'. |
| |
| Battery
voltage is 389. Battery temperature is 24.2 Celsius. |
| |
| The
race is 34.34 miles plus 4.04 miles of pace lap and cool down. |
| |
| We
set the current limit to 400 amps. Count 505 watts for the pace lap
and 824 per mile, we should use 28.801 kw. We decide to bump the regenerative
braking current from 200 amps to 300 amps to try and give us a cushion.
|
| |
|
We
line up in the 40th grid position.
|
 |
| |
| I
am conservative into the first turn. There are a lot of cars crowding
through one corner. I cut through traffic and pass 7 cars in the first
lap. By lap 5, I am 4th in class - 23rd overall. |
| |
| working
traffic video (~1.34MB .wmv file) |
| |
| Lap
6, I turn my fastest lap, a 1:26.719. |
| Lap
9, I am lapped by the leaders. |
|
Lap 14, I turn a 1:26.756. 0.043 slower than my fastest lap, despite
having 10 less horsepower. |
| |
| fast
lap video (~31.56MB .wmv file) |
| |
| Going
through the last corner, I feel a drop in power. |
|
The voltage has sagged to 270 under load and the inverters are limiting
the current to protect the batteries. The current goes down to below
200 amps but I am still at over 90 Mph (5303 rpm) when I cross the
finish line. I have finished 4th in class and 15th over all. Not a
bad result starting from the back of the pack. |
| |
 |
| |
|
End
voltage is 313 volts. Highest battery temperature is 56 degree Celsius.
The pack has delivered 31.595 kW-hrs from a pack rated for 35.150
kW-hrs at a .5C discharge rate. So under race conditions with maxim
discharge set to 400 amps and maximum regenerative braking currents
set to 300 amps, we are able to utilize 89.9% of the rated capacity.
This is very impressive.
It
is great to finish another 30 + mile race. The car ran hard and
we continue to learn more about racing an electric car.
|
| |
 |
| |
| We
jack up the car and start prepping for tomorrow. Late in the race,
I noticed the car rolling more and actually sitting on the right rear
bump stop coming out of turn 5. The body roll was extreme enough to
cause some more minor rubbing. We inspect the tires. |
| |
 |
| |
|
We
can cure this by adding a small wheel spacer.
Even
more serious are blisters on the rear tires.
|
| |
 |
| |
|
Roebling
Road is hard on tires and the Electric Imp is heavier than optimum
for this compound. These blisters are caused by the tires overheating
and rubber seperating from the belts.
This
is odd. The car was still not turning in well and understeering
mid-phase and on exit. Yet, despite the understeer, it is the rear
tires that are blistering.
It
is possible that I am hurting the rear tires breaking them free
under braking to pivot the car. We must get rid of the understeer.
We decide to try full stiff on the rear anti-roll bar and we raise
the gas pressure on the rear shocks.
We
mount new tires for qualifing. And up the amps to 500.
After
about 1.5 hours battery temperatures have dropped below 45 degrees
(C). Four hours later, the pack is fully charged. 392.4 volts at
38.7 degrees.
|
| |
|
 |
