Hi folks,
So I'm trying to understand why it seems to take 30-ish % more time to charge my car than what I calculate it to need.
Scenario: charged from 69% to 85% SoC (per the logs) in 1hr 32 minutes. Charging was at 30 amps / 240 volts (7.2kw), in Range mode. This was after a 70 mile freeway drive that was mostly down-hill, so the car wasn't panting.
So, by the math, I should have added 16% of the battery's capacity, or 8.5 kwh (0.16*53kwh). At a 7.2kw rate, I should have needed just 1hr 11 minutes to accomplish the charge, plus a little for inefficiencies. The logs for the event shows that I actually consumed 11.2kwh. Now, 7.2kw for 1.5hrs is 10.8kwh. So, the difference between 10.8 and 11.2 is likely that charging inefficiency (4%). But that 10.8kwh should match the 16% of 53kwh, and it's not even close. Why the difference between 8.5 and 10.8?
I read Tom Saxton's very informative article (Tesla Roadster Charging Rates and Efficiency - Tom Saxton's Blog), but it predicts the lower number too. 16% charge * 530 wh/% is 8.5 kwh needed.
Is this a matter of having an older battery (CaC of 140 vs 160 new), or the A/C coming on (I don't recall it doing that, but perhaps it did a little), or something else? Any way to better predict this for Roadsters in general? What information is needed?
Thanks,
Greg
So I'm trying to understand why it seems to take 30-ish % more time to charge my car than what I calculate it to need.
Scenario: charged from 69% to 85% SoC (per the logs) in 1hr 32 minutes. Charging was at 30 amps / 240 volts (7.2kw), in Range mode. This was after a 70 mile freeway drive that was mostly down-hill, so the car wasn't panting.
So, by the math, I should have added 16% of the battery's capacity, or 8.5 kwh (0.16*53kwh). At a 7.2kw rate, I should have needed just 1hr 11 minutes to accomplish the charge, plus a little for inefficiencies. The logs for the event shows that I actually consumed 11.2kwh. Now, 7.2kw for 1.5hrs is 10.8kwh. So, the difference between 10.8 and 11.2 is likely that charging inefficiency (4%). But that 10.8kwh should match the 16% of 53kwh, and it's not even close. Why the difference between 8.5 and 10.8?
I read Tom Saxton's very informative article (Tesla Roadster Charging Rates and Efficiency - Tom Saxton's Blog), but it predicts the lower number too. 16% charge * 530 wh/% is 8.5 kwh needed.
Is this a matter of having an older battery (CaC of 140 vs 160 new), or the A/C coming on (I don't recall it doing that, but perhaps it did a little), or something else? Any way to better predict this for Roadsters in general? What information is needed?
Thanks,
Greg