Hard Driving on the Highway

Time Posted on October 04, 2010 User ChargeCar Team

This morning the Civic was taken out for another round of hard driving, mostly highway driving up and down Greentree Hill.  Four laps were made back and forth on I-376 between Route 51 and Carnegie, roughly 8 miles per lap.  The car has no problem keeping up with traffic.  Current went as high as 450 A when climbing the hill at 55 mph.  Total mileage was 42.7 miles, using 10.62 kWh, 1.86 kWh regen (17.5%), giving us about 4.87 miles per kWh!

One reason for the hard driving test was to check the temperature increases on the motor, controller, and batteries so we can make good design decisions for future conversions.  The starting temperature for the components was approximately 60-65 F (16-18 C).  The outside temperature at 11 AM was about 55 F (13 C).  Temperature data was recorded at the end of the drive from sensors we have installed ourselves (reported to the "display"), from the controller/BMS (reported to the Curtis programmer/"monitor"), and from a non-contact pyrometer:

  Display Monitor Pyrometer
Motor Temp. 93 F (34 C) 127 F (53 C) 129 F (54 C)
Controller Temp. 86 F (30 C)    
Max. Battery Temp. 111 F (44 C)   105 F (41)

*The discrepancy in motor temperature measurements is explained by the different sensor locations; the "display" temperature is measured on the exposed end of the motor, "monitor" temperature is read from a sensor located, and the pyrometer reading is based off of the motor casing.  The "display" temperature sensor should probably be relocated to a hotter location in the future.

Battery temperature climbed higher than it ever has before, not surprising given the severity of the test.  The battery pack is fully enclosed in a plywood box to contain as much of the heat as possible.  The total increase in temperature was about 47 F (26 C), approximately 54 F (30 C) above ambient temperature.  This heating corresponds to approximately 4% of the net energy consumption.  Even if driven on a hot day (say, 100 F or 38 C), the battery temperature (perhaps 64 C) should be well below the 75 C operating limit recommended by Thunder Sky.  This is more strong evidence that the our battery pack will not require cooling or ventilation.

We will be analyzing the data to see if there is a significant gradient in cell temperature between the middle of the pack and the outside. We will also be using the GPS data to extract topography information from the commute, specifically the grade.

The great takeaway message is that the Civic is suitable for highway driving, even with steep hills and high ambient temperatures!

 

[UPDATE]

Recharging consumed a total of 11.27 kWh.  8.76/11.27 = 78% efficiency.  In units probably more useful to potential conversion drivers, this means that on hard drives, our car managed 42.7 miles using 11.27 kWh of energy (potentially from your wall outlet), giving us about 3.79 miles per kWh of charging.  If we assume that cost per kWh is about $0.10 (Duquesne Light claims $0.0817/kWh for most residential customers; www.duquesnelight.com/ElectricChoice/calculate.html), then you can see that once your car is converted, $1 of electricity gets you about 38 miles of range.  According to www.pittsburghgasprices.com, cheap gas in Pittsburgh costs $2.61/gallon; in a 25 mpg ICE car, you are spending at least $3.96 to go the same distance.  Interesting.

Cat News Tag honda

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