March 25, 2005

Moroso Test Day -Friday

Session 1 (run #1)

Our first goal is to get some firm figures on power usage per lap. The battle plan for the first twenty minute session is:

- set the current limit to 50% (300 amps).
- do a hot 'out' lap.
- do a hot timed lap.
- do a hot 'in' lap.
- get data.
- reset power to 67% (400 amps).
- hot 'out' lap, Hot timed lap, hot 'in' lap.

We will then have twenty minutes to check over the car before we repeat the session at 83% (500 amps) and 100% (600 amps).

Naturally this plan does not survive contact with reality.

I go out hot.
While I know most of the track well, the chicane (turn 8) is pretty new to me.
I come in hard, over rotate the car under braking on fairly cold tires and go for a quick spin.
I gather the car up and continue.

The timed run goes off just fine.
I turn a fairly anemic 1:58 but without any drama.
Top speed is 108 MPH.
The car oversteers but is drivable.

The pit stop is quick.
Computer data is checked and saved.
The crew does a walk around looking for anything amiss.

Session 1 (run #2)

The Siemens inverters have a neat capability that allows you to choose between two preset current limits with a switch.

We started with a 300 amp limit. Flick two switches (one for each inverter) and I go out again with a 400 amp limit. The car dances with the extra power.
The tires are hot, so the 'out' lap gives me some idea what the car is capable of.

The timed lap is a 1:50.
Top speed 116 MPH.
Better driving, hotter tires, more power.
This is closer to a competitive time.

- Record tire temperatures.
- Record tire pressures.
- Save computer data.
- Back to the paddock area

The crew softens the rear anti-sway bar two steps to fix the oversteer and adjusts tire pressures, which, according to tire temperatures, are too high.

The big issue is the power usage per lap.

We take total power used (Kw-hrs) and divide by 3 laps.
At half power (300 amps), the car uses 1.894 kw-hrs per lap.
This is .842 kw-hrs per mile or over three times what we use on the street.

The 2/3 power laps are even worse. 2.101 kw-hr per lap, .934 kw-hr per mile.

The six laps have already used 12 kw-hrs of our 22.7 kw-hr pack.

To check our calculations we look at pack voltage. It is 329 volts or 3.74 volts per cell. Based on our 70 amp discharge study, this indicates that we have slightly less than 50% charge left.

Later reviewing the data, we notice that cell #17 was often the lowest. In fact under load, it dropped occasionally under 1 volt. Cell #9 once dropped to 2.9 volts but no other cell dropped below 3 volts. By the end of the session, #17 had recovered to 3.426.

We decide to skip the next session and put the car on charge for an hour. We have used about 37 amp-hrs.

Electric Imp being recharged

Our generator is the limiting factor in our charging this weekend.

The Honda 3000 can provide 12.5 amps at 240 volts or about 7.5 amps into the pack.

30 minutes into the charge, #17 has gone from lowest voltage cell to highest. It now seems likely it was damaged.

An hour charge gives us back 7.5 amp-hrs. Call it 40 amp-hrs or 57% left. Check with pack voltage 335 volts or 3.81 volt per cell. Based on our 70 amp discharge study, this indicates that we have slightly more than 60% charge left.

A quick calculation for the race tomorrow:

14 laps times 1.894 Kw-hrs is 26.5 kw-hrs or 3.8 kw-hrs more than we have in a 100% full pack.

We will need to run less power to finish the 14 lap race.

We reset the inverters lower to test at 33%, 200 amps.



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March 25-27, 2005 PreRace
March 25, 2005 Session 2


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