Wall and mobile connector voltage measurement accuracy

[TikiSteve]

Power loss is I^2 * R and R= delta V / delta I

so you can set two different charging currents, record delta v and I. Presto! You have the resistance right to the charger and can now calculate power loss. Well I did this with the mobile connector on a circuit I extended and it came up way high.... 0.35 ohms. So I think this is high, but the distance to the box is 50ft, plus zigs and zags with #10, so high but possibly believable.

Next I install a wall connector, 35 feet of #6, terminated in the panel and hardwired on the wall connector. Repeat calculation... 0.2 ohms??? 10x what it should be. I am convinced the voltage measurement is poor for sure on the wall connector, possibly on the mobile. Comments??

 

[Big Earl]

Power loss is I^2 * R and R= delta V / delta I

so you can set two different charging currents, record delta v and I. Presto! You have the resistance right to the charger and can now calculate power loss. Well I did this with the mobile connector on a circuit I extended and it came up way high.... 0.35 ohms. So I think this is high, but the distance to the box is 50ft, plus zigs and zags with #10, so high but possibly believable.

Next I install a wall connector, 35 feet of #6, terminated in the panel and hardwired on the wall connector. Repeat calculation... 0.2 ohms??? 10x what it should be. I am convinced the voltage measurement is poor for sure on the wall connector, possibly on the mobile. Comments??

Are you reading the voltage in the car/app? If so, both of those are rounded to the nearest whole number. The power display in kW is also rounded to the nearest whole number. Not exactly accurate.

 

[MP3Mike]

I am convinced the voltage measurement is poor for sure on the wall connector, possibly on the mobile. Comments??

If you are looking at what is displayed in the car, I suspect that is from the on-board charger. Not coming from the Wall connector or mobile charger. (I think the Wall connector does have a web interface that reports voltage.)

 

[TikiSteve]

I missed the forest through the trees, I think you nailed it Mike. Based on the known variables, I will speculate the flexible cord approved for 42 amps on the wall charger is #12 wire! The numbers also say the power dissipated in that cord is 260 watts at 42A (about 2% of delivered power). Pretty crappy in my book.