PERFORMANCE

Quest for an Electric Porsche Boxster.

The car is really fun now. Except for range and battery capacity, the car is meeting expectations as far as performance. After emailing Tim Catellier who has a lot of experience with his BMW Z3, and discussing the batteries with David Anderson at K2, I decided to reduce the low voltage limit on the Zilla to an average of 2.3V. This really loosened up the amp output, and now I am getting close to 840A on demand, and more rapid output overall. That means more acceleration! I roughly measured 0-60 times using my cell phone's stopwatch, and on relatively flat ground I am seeing less than 7 seconds, maybe 6, in optimal conditions. That means a full pack and relatively warm weather. The battery voltages sag on heavy load, with the lowest blades at 2.3-2.4V, and an average minimum of around 150V. So one must wonder what the car would be like with a higher nominal voltage pack, say 260V? This would help cold weather performance too.

Austin, Texas has been rather cold in recent days. Last Wed, the temp dropped below 25 degrees. I left home with a half full pack and kept the car garaged that night. So the pack was relatively warm. But at the end of the day, the car was in less than 23 degree weather parked outside, not plugged in. The car was sluggish, and getting on the freeway was barely possible. The car requires about 100-130A to maintain speed on the freeway on level road or with slight elevations. The pack would not produce more than about 160A on the way home limiting acceleration severely. Granted the pack was more than half empty, but compared to warm weather this was a dramatic loss of power. Despite average voltages sagging as low as 2.3v, I was able to get home and the voltages returned to over 3.1v at rest. I tested range in warm weather the next day, and capacity was back at 72Ah. So it was evident the batteries can tolerate battery sag, at least above 2V briefly, without serious problems. So yesterday I decided to drop the Zilla limit to an average minimum of 2.3V. Now in warm weather the car feels like a PORSCHE. Much better than stock! I imagine driving like that may limit range even more, but it's worth it!