Event - REFUEL at Mazda Raceway Laguna Seca 07/01/12

[TomT]

Just don't race in AZ or TX!

For a vehicle without thermal management, the LEAF's ability to run cool is striking. The MINI E had a temp alarm (>114°) after 3 laps last year and was over 125° in the pits before starting to cool.

[adrianco]

Hi Nader,

I pushed the Traction Control button to turn it off before each run on the track and didn't feel any ESP cutting in. In normal mode it cuts power as soon as the car slides a bit, but I was able to drift the car a bit in turn 4 without noticing any ESP issues.

What springs and shocks are you running? I've got the Tein coil overs and its a nice upgrade for street use and twisty mountain roads.

[tbleakne]

>> the Gid meter shows that 30 kW power level heats the battery about 1 kW, and 40 kW heats the battery about 1.8 kW.

your heat loss estimates look a bit high: I'm getting about half that using 400V pack voltage and 100 mOhm internal resistance.

The battery impedance can vary, but I am confident that my calculation is reasonably close (+- 20%) because it is based upon the DC voltage drop I have observed under load with the Gid meter.

Since my post I realized we can calculate the worst-case temperature rise from battery discharge by neglecting all heat transfer out of the battery pack.
At 30 KW power level:, using my approximate measurement of 1% loss for each 10 kW:
(30 kW)*(1 % per 10 kW [measurement])*(30 kW) = 3% of 30 kW = .9 kWh per hour = .015 kWh per min
(.015 kWh per min)*(3,412 BTU/kWh) = 51 BTU/min
For a 650 lb battery pack, this yields (51/650) = .079 deg F per min, or 2.4 F rise at 30 kW for 30 minutes.

At 50 kW power level, battery loss scales quadratically, so we have (50/30)^2 * 2.4 = 6.6 F at 50 kW for 30 min.

The same process that causes the t^.5 loss of capacity also raises the battery impedance, so this heating will rise with age, but it should still not be a concern under most circumstances.

The graph I posted in another thread shows the impedance rising rather rapidly at very low SOC, so high power down here is not advised (and ultimately limited by the BMS). It also shows the charging process as being slightly endothermic at low SOC levels, and then becoming exothermic as the SOC level rises. This is consistent with the QC tapered charging profile.

The picture of the Tesla roadsters cooling off after short runs at high power was dramatic. The Tesla S is supposed to have more robust cooling of both its battery and motor.

[TEG]

...The picture of the Tesla roadsters cooling off after short runs at high power was dramatic. The Tesla S is supposed to have more robust cooling of both its battery and motor.

Don't forget the inverter ("PEM"). The Roadsters' air cooled inverter is one of the more likely components to overheat at the track. The Model S liquid cools the battery/pack, motor, and inverter.

[Boomer23]

Not sure if anyone's posted this YouTube video of Jack Brown's run in the BMW that started behind Tony. The video has the first half of Tony's run shot from directly behind Tony for 3 or 4 laps. I pulled it off the Facebook BMW ActiveE page where I'm a member. Jack said "I couldn't get the LEAF to let me by before I thermal limited." Hmm...

Anyhoo, it's a great look at the first half of Tony's run from directly behind him and shows Tony passing at least one BMW and getting passed by the race prepped Coda, but not without a fight.

Later in the video, you get to see three Tesla Model S scream by Jack with a Volt embedded in their pack, probably scared sh*tless.

Tony, well done in that bone stock LEAF. You da man!


http://www.youtube.com/watch?v=nyMa-pCruMo" onclick="window.open(this.href);return false;

[Boomer23]

Here are two videos from Don Louv's BMW. Don seems to be a really fast and efficient driver. In the first video, he out drags Nader at the beginning and gives a Tesla Roadster a run for his money. This was Don's fast lap, at 2:05.

Watch these at full screen size. Really a fun ride, almost like playing Gran Turismo on Play Station.


http://www.youtube.com/watch?v=I-iK96AfLTE" onclick="window.open(this.href);return false;

In the second video, Don's BMW was overheating and limiting his power. Nader blows by him at the end of the run. He gave Nader good props on the ActiveE Facebook page.

http://www.youtube.com/watch?v=QFHJ_8nRGKQ" onclick="window.open(this.href);return false;

[Nubo]

With all this talk about thermal issues for the "thermally managed" cars at the track, I am finding new respect for the LEAF. The Phoenix cars are still a concern, of course.

[ttweed]

Does the car have a sub 2 minute lap time in it with race rubber? We'll have to see about that next year...

I am positive it does, if you were using the 615 Azenis. My experience is that the Kumho V710 will give you 2 seconds gain for every one minute of course length over those tires, so that change alone should put you at 1:58.

So even if you turn traction control off, it will kick back in automatically if the car detects high slip angles or yaw? I hate electronic nannies that can't be disabled. There must be an electronic hack for that--what did they do with the Pike's Peak car?

TT

[gascant]

Great pics by all who posted. Thanks a lot! I'm putting "Refuel 2012 Recap" on the agenda for next Saturday's SF BayLEAFs meeting. Anyone want to show up and relate their experiences?

In Tony's video, you can see him roaring past me, driving the track's only silver LEAF. Small wonder that I finished last among the LEAFs--I guess I didn't trust the car (and brakes) enough. In retrospect, I let off the accelerator far too early and lost a lot of speed around the turns. As a result, I was only able to get speeds of around 70 MPH up the straightaways.

[KeiJidosha]

...The picture of the Tesla roadsters cooling off after short runs at high power was dramatic. The Tesla S is supposed to have more robust cooling of both its battery and motor.

Don't forget the inverter ("PEM"). The Roadsters' air cooled inverter is one of the more likely components to overheat at the track. The Model S liquid cools the battery/pack, motor, and inverter.

Tesla roadster and ActiveE would probably have benefited from ability to turn off regenerative braking. As you brake into a corner the motor, inverter and batteries are at full regen, recycling a lot of the power (and heat) you just dumped thru them to get the car up to 90mph. Ability to turn off regen could have reduced the heat load by ~30%. Assuming the brakes were up to the task by themselves.