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bwilson4web · 10-01-2011, 03:25 PM

Could you give a rough time-line of the events with attention to:

temperature, external and cabin
distance / time (if off)
estimated speed
use of EV button
terrain features, 10m, 20m, 50m, 100m, 200m hills

I have noticed my wife's ZVW30 car maintains different traction battery charge levels depending upon speed and to some extent the terrain.

Above 73 km/h (~46 mph,) on fairly flat land, 10-20m hills and overpasses, the battery reaches the nominal ~60% charge level fairly quickly, 5 km (~3 miles.) But at slower speeds, 40 km/h (~25 mph,) it seems to let the traction battery level go to lower levels. Knowing roughly the speeds on the different segments, I can more closely approximate the original drive protocol.

We've had a cold front come in and scattered frost is in the forecast. We also live near the Piedmont plateau and close to the foothills of the Appalachian mountains. We also have Tennessee River bottom land so I suspect I can find routes and in the fall, weather conditions that somewhat approximate your drive.

SPECULATION/HYPOTHESIS

There are times when the car needs to put a charge on a traction battery that reaches some low threshold. The symptom is the engine runs when stopped instead of being off. During these times in our NHW11, MG1 (also called the generator) needs engine torque to make the charging power. When stopped, the brakes or in "P" the parking paw provides the counter torque needed to let engine power flow to MG1. At low speeds, MG2 can provide that counter torque.

There may be some subtle window at slow speed or when starting from a dead stop when the necessary MG2 torque is not available but the car needs to put a charge on the traction battery. If not balanced by MG2, the necessary torque would come from the gearing connected to the wheels. It would seem as if the car were accelerating without input from the accelerator. (NOTE: I am not ruling out anything including a mechanical 'sticky' event which is why the temperature is important.)

During the event, did the engine rpm give an impression of medium, high or very high rpm? I know this is imprecise but without a Scangauge or equivalent instrumentation . . . Did it sound like you were climbing a steep hill?

Thanks,
Bob Wilson

10-01-2011, 03:25 PM	#25 (permalink)
bwilson4web Engineering first Join Date: Mar 2009 Location: Huntsville, AL Posts: 851 17 i3-REx - '14 BMW i3-REx Last 3: 45.67 mpg (US) Blue Bob's - '19 Tesla Std Rng Plus Thanks: 98 Thanked 251 Times in 160 Posts	Could you give a rough time-line of the events with attention to: temperature, external and cabin distance / time (if off) estimated speed use of EV button terrain features, 10m, 20m, 50m, 100m, 200m hills I have noticed my wife's ZVW30 car maintains different traction battery charge levels depending upon speed and to some extent the terrain. Above 73 km/h (~46 mph,) on fairly flat land, 10-20m hills and overpasses, the battery reaches the nominal ~60% charge level fairly quickly, 5 km (~3 miles.) But at slower speeds, 40 km/h (~25 mph,) it seems to let the traction battery level go to lower levels. Knowing roughly the speeds on the different segments, I can more closely approximate the original drive protocol. We've had a cold front come in and scattered frost is in the forecast. We also live near the Piedmont plateau and close to the foothills of the Appalachian mountains. We also have Tennessee River bottom land so I suspect I can find routes and in the fall, weather conditions that somewhat approximate your drive. SPECULATION/HYPOTHESIS There are times when the car needs to put a charge on a traction battery that reaches some low threshold. The symptom is the engine runs when stopped instead of being off. During these times in our NHW11, MG1 (also called the generator) needs engine torque to make the charging power. When stopped, the brakes or in "P" the parking paw provides the counter torque needed to let engine power flow to MG1. At low speeds, MG2 can provide that counter torque. There may be some subtle window at slow speed or when starting from a dead stop when the necessary MG2 torque is not available but the car needs to put a charge on the traction battery. If not balanced by MG2, the necessary torque would come from the gearing connected to the wheels. It would seem as if the car were accelerating without input from the accelerator. (NOTE: I am not ruling out anything including a mechanical 'sticky' event which is why the temperature is important.) During the event, did the engine rpm give an impression of medium, high or very high rpm? I know this is imprecise but without a Scangauge or equivalent instrumentation . . . Did it sound like you were climbing a steep hill? Thanks, Bob Wilson __________________ 2019 Tesla Model 3 Std. Range Plus - 215 mi EV 2017 BMW i3-REx - 106 mi EV, 88 mi mid-grade Retired engineer, Huntsville, AL Last edited by bwilson4web; 10-01-2011 at 03:30 PM..