Is this normal for home charging?

[roblab]

It doesn't always warn, in my experience.

90 ft of #6 running from a sub-panel with a ???A main and #? wire of ??ft to the main panel is probably enough to cause a pretty substantial voltage drop even with nothing else running let alone normal loads (especially resistive electric aux heat). You're looking at 4-5V drop just in the 90 ft of #6 @ 40A, plus a drop in whatever the run from the subpanel is to the main panel. Plus a drop when adding in the subpanel loads and main panel loads.

My limited information says #6 is good for 50 feet. He's on the edge, at least.

At my garage, I have been charging at 40 amps for two years, and now it only does 30 amps. So I don't think it's the wire, in my case. But 90 feet of #6 is interesting. Off a sub panel. Yeah. Interesting.

 

[wk057]

Thanks for explaining that so well....I never knew much about voltage drop...sub panel is 100amp and is a 60 foot run from main panel. If I would have run direct from the main panel it would have been a 150-170 foot run, so I'm not sure if I would have been any better off, and running #4 that distance would have cost a fortune. I can live with charging at 30amps, I am just trying to determine if its likely an error my installer made, a defect in the car or UMC, or just my general setup/household load that is to blame. I'm glad the UMC is that smart to throttle down for potential issues.

Oh boy, yes for sure you'd need at least #4 from the main panel for this IMO. My guess is your installer never factored in a continuous 40A draw and the extra length from the main panel to sub panel.

If you're going to leave it as is, I would set your charge rate to 30A max to be safe. The car may still complain though.

If you ever were to run a HPWC you'd need #1 wire most likely to account for the long run from the main panel... if you wanted 80A charging.

You could always change the NEMA 14-50 to a HPWC and set the dip switches for a 40A circuit, which would limit charging to 32A. The HPWC has #6 wire in the cable, so slight benefit there.

 

[mackgoo]

After reading this I decided to charge the car and see what happens. I started at 72%. It's been charging at 235v/40A steady state.

 

[hingisfan]

Oh boy, yes for sure you'd need at least #4 from the main panel for this IMO. My guess is your installer never factored in a continuous 40A draw and the extra length from the main panel to sub panel.

If you're going to leave it as is, I would set your charge rate to 30A max to be safe. The car may still complain though.

If you ever were to run a HPWC you'd need #1 wire most likely to account for the long run from the main panel... if you wanted 80A charging.

You could always change the NEMA 14-50 to a HPWC and set the dip switches for a 40A circuit, which would limit charging to 32A. The HPWC has #6 wire in the cable, so slight benefit there.

Sometimes the most obvious solution is the correct one.

I plugged in tonight and checked...somehow the limiter was set to 30A on the car.

I feel like an idiot. Charging now at 227-228V / 40A...Is it ok to run it like this?

Thanks for the electrical education.

 

[jerry33]

Sometimes the most obvious solution is the correct one.

I plugged in tonight and checked...somehow the limiter was set to 30A on the car.

I feel like an idiot. Charging now at 227-228V / 40A...Is it ok to run it like this?

Thanks for the electrical education.

1. The Model S will set the limiter to 30 amps if it detects a power drop.

2. If you charge at 40 amps and it detects a power drop it will drop the limiter back down to 30 amps.

3. When there is questionable wiring (RV parks are a prime example) set to 32 or 33 amps. There isn't much difference in the charge time and the RV park breaker won't trip. If your house is in an area of poor power do the same.

My house is in an area of poor power, the lights flicker so badly that I have a 6 KVA UPS to run the electronics--and yes, I asked and all the electricians (and other Tesla owners) say every house in my area is similar, so it's nothing to do with the house wiring and everything to do with the electric supplier. If I set the limiter at 40 amps, it would just go back down to 30. At 33 amps it stays charging without falling back.

 

[hingisfan]

1. The Model S will set the limiter to 30 amps if it detects a power drop.

2. If you charge at 40 amps and it detects a power drop it will drop the limiter back down to 30 amps.

3. When there is questionable wiring (RV parks are a prime example) set to 32 or 33 amps. There isn't much difference in the charge time and the RV park breaker won't trip. If your house is in an area of poor power do the same.

My house is in an area of poor power, the lights flicker so badly that I have a 6 KVA UPS to run the electronics--and yes, I asked and all the electricians (and other Tesla owners) say every house in my area is similar, so it's nothing to do with the house wiring and everything to do with the electric supplier. If I set the limiter at 40 amps, it would just go back down to 30. At 33 amps it stays charging without falling back.

Would it still be set to 30 amps the next day if the car changed it to 30?

Running VisibleTesla now so I should be able to see it graphed if this happens now. Amazing program by the way.

 

[jerry33]

Would it still be set to 30 amps the next day if the car changed it to 30?

Yes. It will stay set at 30 until manually changed--that's how you can tell it thought there was a problem.

 

[hingisfan]

Yes. It will stay set at 30 until manually changed--that's how you can tell it thought there was a problem.

Thanks...I'll see how it goes the next few days...this charge seems to be fine at 40amps.

 

[Doug_G]

Would it still be set to 30 amps the next day if the car changed it to 30?

Yes. Unfortunately the car remembers the reduced setting.

 

[Canuck]

Yes. Unfortunately the car remembers the reduced setting.

Or fortunately it does, at least for me. I put a 14-50 plug on a HPWC, set the dips to 63 amps, and then dialed the car down to 45amps. It would be a real hassle to have to dial it down every time I charge.

 

[Doug_G]

No, it's good that it remembers what YOU dialed it down to. It's annoying that it remembers when the CAR did it. Especially since I get false triggers fairly frequently at the office.

The back-off algorithm is fundamentally flawed because it doesn't seem to realize when the car is charging from 208V 3-phase source versus 240V 2-phase source. The open-circuit voltage for 3-phase systems can be in the very low 200's. If it drops much under 190 it false triggers. That can happen under load simply due to variations in the source power from hydro - nothing to do with the reliability of the local circuit.

 

[Canuck]

No, it's good that it remembers what YOU dialed it down to. It's annoying that it remembers when the CAR did it.

Ahh, yes, agreed.