Hi,
We are investigating cold weather performance of the Prime. Living in Dixie, we only have a couple of weeks to test cold soaking.
BELOW 50F (10C)
We found undocumented:
Use "," and "." to step back and forward single frames. When the EV car icon changes from solid to an outline, the engine is running. The engine is too quiet to depend on hearing it.
BELOW 14F (-10C)
Well documented, the heat pump cabin heater can not provide enough heat. So the engine runs to provide the heat needed. However, keeping the car in "EV mode" allows the car to frequently enter EV mode:
We found video recording is critical to documenting the problem. Humans can notice the problem but their descriptions often include 'noise' that has to be filtered out. Video recording is key.
We tried to use Goggle Earth to get grade information on routes for hill climbs. Unfortunately Google Earth wanders +/- 5m from the graphical route. This leads to amusing profiles where the car apparently does not use the bridge but appears to drive down the bank to cross a creek and up the other side. It is worse on a hill side route where Goggle Earth reports impossible grades, 78%, as it shows the car driving up the hill side. It is significantly worse than GPS wander which have their problems but the error is much less. I also have a six-axis accelerometer, 400 Hz sample rate, that can provide even better grade resolution.
SUMMARY
We don't find this cold weather performance to be a serious problem as much as it is poorly or undocumented including how to minimize the problem. We can still get full battery performance in the 14F to 50F (-10C to 10C) range provided we know the risks and restart the car. On the gas engine, the car still has +600 mile range.
Bob Wilson
We are investigating cold weather performance of the Prime. Living in Dixie, we only have a couple of weeks to test cold soaking.
BELOW 50F (10C)
We found undocumented:
- cruise control and SOC 90% - setting cruise control when the battery SOC is above 90% causes an undocumented "engine ON" event. The car remains in "EV mode" but the engine starts a 3-4 minute engine warm-up cycle. For a 10 mile commute this can kill mileage even with plenty of energy in the battery.
- ascending some grades - under investigation, we are using iPhone GPS and six-axis accelerometer to get better grade metrics.
- descending some grades - also under investigation, not previously documented in the Prime.
Use "," and "." to step back and forward single frames. When the EV car icon changes from solid to an outline, the engine is running. The engine is too quiet to depend on hearing it.
BELOW 14F (-10C)
Well documented, the heat pump cabin heater can not provide enough heat. So the engine runs to provide the heat needed. However, keeping the car in "EV mode" allows the car to frequently enter EV mode:
- 10-14F (-12 to -10C), 20 mile (32 km), loop
- 80 MPG, 51% EV mode
We found video recording is critical to documenting the problem. Humans can notice the problem but their descriptions often include 'noise' that has to be filtered out. Video recording is key.
We tried to use Goggle Earth to get grade information on routes for hill climbs. Unfortunately Google Earth wanders +/- 5m from the graphical route. This leads to amusing profiles where the car apparently does not use the bridge but appears to drive down the bank to cross a creek and up the other side. It is worse on a hill side route where Goggle Earth reports impossible grades, 78%, as it shows the car driving up the hill side. It is significantly worse than GPS wander which have their problems but the error is much less. I also have a six-axis accelerometer, 400 Hz sample rate, that can provide even better grade resolution.
SUMMARY
We don't find this cold weather performance to be a serious problem as much as it is poorly or undocumented including how to minimize the problem. We can still get full battery performance in the 14F to 50F (-10C to 10C) range provided we know the risks and restart the car. On the gas engine, the car still has +600 mile range.
Bob Wilson