Sorry for the TL;DR
Over the last few months, I've been curious about charging efficiency for my Model 3P and so I decided to do a small test:
My wife has a very consistent driving schedule with it and so if you tracked from day to day and week to week, the charge level of the car (as well as the at-home charging cycles are very similar over time; i.e. She leaves at a certain time, comes back at a certain time, plugs in at a certain time and the car will charge to the same set level of 65%.
It's to the point where the car basically uses 15-16% charge every weekday, and replenishes that charge starting at the same time of the late afternoon Mon-Fr. Of course there are still the odd trips to other places and longer drives, but in general the car lives at between 50%-65% charge.
Over the past few months, I've varied basically only the AC home charging power level (8-48 amps) on a level II Tesla Wall charger unit. I use the iPhone app "Tessie" to track what it calls "Charging Efficiency" where it see how much power came thru the charger total, and compares that against what the car battery reported it got from that charge session; the closer those two numbers are, the closer to 100% charge efficiency.
I know I can't control things like ambient temperature, or how hot or cold the pack was when the charge actually started, but I tried to hold as many variables as steady as I could, realistically.
Results:
After varying between 4 charge levels several times from dozens of charging sessions at 8, 24, 36, and 48 amps the results are a little surprising to me.
At 8 amps it recovers the 15% charge in 6 hours +/- 10 minutes with an efficiency of 73-81%
At 24 amps it recovers the 15% charge in 2 hours +/- 10 minutes with an efficiency of 76-88%
At 36 amps it recovers the 15% charge in 1 hour 20 minutes +/- 5 minutes with an efficiency of 97-99%
At 48 amps it recovers the 15% charge in 1 hour 5 minutes +/- 5 minutes with an efficiency of 70-77%
I know that the Tessie app as well as the Tesla itself is not really measuring, with closed-loop accuracy, the state of charge of the pack, and much of the data is actually "interpolated" (like range in miles), but I still found the results very compelling with 36 amps seemingly being a sweet spot, and 8 amps being too little to not have large losses during a longer charging session (or perhaps just too low a current to get very accurate readings?) and 48 amps for some reason suffering large losses during shorter charging sessions even though 48 amps AC is FAR below the charging capacity of the pack. (Could it be resistance building in the charger and the charge wire itself? Since it only gets "Warm" at charge levels approaching its' max of 48 amps)
Anyhow, I was wondering if anyone else tracks these kinds of numbers and has seen anything even remotely similar. I'll try another test run starting in the middle of summer, and I want to see if the efficiency numbers just all skew upwards at the same rate given temperature. Until then, I've left the wall charger set at 36 amps and consistent with prior test, it constantly reports a charging efficiency always in the 90's and the several times I needed a quicker boost at 48 amps, the efficiency is always much lower.
"Tesla Model 3 Supercharging board computer in the car during the charging phase" by verchmarco is licensed under CC BY 2.0.
Admin note: Image added for Blog Feed thumbnail
Over the last few months, I've been curious about charging efficiency for my Model 3P and so I decided to do a small test:
My wife has a very consistent driving schedule with it and so if you tracked from day to day and week to week, the charge level of the car (as well as the at-home charging cycles are very similar over time; i.e. She leaves at a certain time, comes back at a certain time, plugs in at a certain time and the car will charge to the same set level of 65%.
It's to the point where the car basically uses 15-16% charge every weekday, and replenishes that charge starting at the same time of the late afternoon Mon-Fr. Of course there are still the odd trips to other places and longer drives, but in general the car lives at between 50%-65% charge.
Over the past few months, I've varied basically only the AC home charging power level (8-48 amps) on a level II Tesla Wall charger unit. I use the iPhone app "Tessie" to track what it calls "Charging Efficiency" where it see how much power came thru the charger total, and compares that against what the car battery reported it got from that charge session; the closer those two numbers are, the closer to 100% charge efficiency.
I know I can't control things like ambient temperature, or how hot or cold the pack was when the charge actually started, but I tried to hold as many variables as steady as I could, realistically.
Results:
After varying between 4 charge levels several times from dozens of charging sessions at 8, 24, 36, and 48 amps the results are a little surprising to me.
At 8 amps it recovers the 15% charge in 6 hours +/- 10 minutes with an efficiency of 73-81%
At 24 amps it recovers the 15% charge in 2 hours +/- 10 minutes with an efficiency of 76-88%
At 36 amps it recovers the 15% charge in 1 hour 20 minutes +/- 5 minutes with an efficiency of 97-99%
At 48 amps it recovers the 15% charge in 1 hour 5 minutes +/- 5 minutes with an efficiency of 70-77%
I know that the Tessie app as well as the Tesla itself is not really measuring, with closed-loop accuracy, the state of charge of the pack, and much of the data is actually "interpolated" (like range in miles), but I still found the results very compelling with 36 amps seemingly being a sweet spot, and 8 amps being too little to not have large losses during a longer charging session (or perhaps just too low a current to get very accurate readings?) and 48 amps for some reason suffering large losses during shorter charging sessions even though 48 amps AC is FAR below the charging capacity of the pack. (Could it be resistance building in the charger and the charge wire itself? Since it only gets "Warm" at charge levels approaching its' max of 48 amps)
Anyhow, I was wondering if anyone else tracks these kinds of numbers and has seen anything even remotely similar. I'll try another test run starting in the middle of summer, and I want to see if the efficiency numbers just all skew upwards at the same rate given temperature. Until then, I've left the wall charger set at 36 amps and consistent with prior test, it constantly reports a charging efficiency always in the 90's and the several times I needed a quicker boost at 48 amps, the efficiency is always much lower.
"Tesla Model 3 Supercharging board computer in the car during the charging phase" by verchmarco is licensed under CC BY 2.0.
Admin note: Image added for Blog Feed thumbnail
