I think I have my doubts if gids are as absolute as we think The highest I've recorded on a 100% charge is 239. If I use that as 100%, then I get only 16.8kWh capacity.Stoaty wrote:Data:
Charged to 80%
Drove 46 miles, using 123 gids (224 gids minus 101 gids)
Charged back to 80% (224 gids again) in 2 hours, 25 minutes (=2.417 hours)
Trip Efficiency (dash) = 5.8 miles/KWh
Total KWh added to battery = 3.3 * 2.417 = 7.975 KWh
1 gid (for my battery) = 7.975/123 = .0648 KWh = 64.8 wh
Total usable battery capacity = 281 * .0648 = 18.2 KWh
As a check on the KWh used for the drive = 46 miles/5.8 miles per KWh = 7.931 KWh (almost exactly the same)
Approaching the problem from the miles driven angle:
Total available miles = 46 * (281/123) = 105.1 miles
Total usable battery capacity = 105.1 miles/5.8 miles per KWh = 18.12 KWh
16A * 240v = 3.84 kW, not 3.3 kW. It is my belief the 3.3 kW is what the charger is capable of delivering to the battery, not what it can accept from the wall.SanDust wrote:Not completely sure I follow how you're calculating this, but the 3.3 kW is what is delivered to the onboard charger not to the battery.
Yes, and 3.3/3.84 = 86% which is very close to the efficiency measured previously for 240 volt charging.planet4ever wrote:16A * 240v = 3.84 kW, not 3.3 kW. It is my belief the 3.3 kW is what the charger is capable of delivering to the battery, not what it can accept from the wall.
Updated Carwings energy usage reports seems to indicate approximately 20.4 KWh capacity was correct as a function of dash (or perhaps nav screen) m/kWh, at least for my car on one day last month, at about 85 F degrees, as I posted below. Of course, that does not mean you are not picking up numbers from somewhere before the CW "usable" or "to the wheels" calculation, as you suggest, and I agree it’s unlikely the dash is reflecting Charging loses.abasile wrote:It seems to me that 18 or 19 kWh could be the amount of usable energy after factoring in discharging losses. Assuming that 24 kWh is the "ultimate" capacity and that the "usable" capacity is closer to 20 or 21 kWh, a discharging efficiency in the ballpark of 85 - 95% could bring us down to 18 or 19 kWh actually available to the motor and accessories.
In other words, it doesn't seem likely that your average efficiency of 5.8 miles/kWh accounts for charging and discharging losses. I believe it is merely an indication of how efficiently the available energy is being used. Of course, with more efficient driving and lower discharge rates, I would expect the discharging efficiency to be higher.
On 9/7 I drove the same route from my home to Burney Falls State Park again at slightly higher speed with more (still not much) AC use. When I reached my driveway, at 87 miles, I still had (less than) one bar, so I drove until I got the "very low battery" warning and simultaneously lost the last bar, at 91.5 miles. I got home with 93.4 miles, and between 5,500 and 6,000 ft. of ascent and descent, at an average speed of about 40 mph (those last 6.4 miles were up and down a hill at low speed). Since the last 1.9 miles after the "very low battery” warning were at about 20 mph and required about 150 ft. net descent with regen, I was probably still very close to the VLBW point capacity, when I parked.
According to CW, on this drive I used 18.7 kWh to drive 91.1 miles at average energy economy of 4.9 m/kWh.
I rechecked 2 other recent drives of 85-105 miles and each time CW has erred, under-reporting distance traveled, as compared with both my odometer and Google Maps, by 2.5%, +/- 0.1%.
Has anyone else-before or after the NTB11-041 update-seen this same odometer/CW mileage disparity?
If so, do you suppose this may reflect the similar discrepancy between the dash and screen numbers, as widely reported?
My car shows 4.3 m/kWh on the dash and 4.4 on the screen, as average since delivery.
Extrapolating from the chart, it appears CW may be saying the 1.7 kWh (8.5% from the chart, of 20.4 total kWh-anyone have a better number?) I had left at or near VLBW implies total available battery capacity of about 20.4 kWh. So, from the limited info I can gather, looks to me that Carwings may now be accurate as to energy use.
Posts from others who can take the charge lower could verify this...
Comments from the SOC meter crowd, and also those who have metered L2 charging and can determine charge efficiency, as a % from Carwings reports, would also be greatly appreciated...
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Interesting thought, but that doesn't square with the reports that the best way to get the actual mileage available to you is to multiply the miles per KWh from the dash by 21 (or 20.4). Although not tested by a complete discharge of the battery, my results suggest that--at least for my car--I should be multiplying the miles per KWh from the dash by 18.2 to get the total miles available on a full charge. Either the rule of thumb needs to be changed, or if the original rule holds true for others then my capacity is lower as indicated by my calculations.abasile wrote:It seems to me that 18 or 19 kWh could be the amount of usable energy after factoring in discharging losses. Assuming that 24 kWh is the "ultimate" capacity and that the "usable" capacity is closer to 20 or 21 kWh, a discharging efficiency in the ballpark of 85 - 95% could bring us down to 18 or 19 kWh actually available to the motor and accessories.