Tesla Vehicle Charging with PV+PW [and no grid]

[Tim-in-CA]

Hello All ... I just got my 8.16kW PV + 2x PW installed and am operating in Backup mode (main breaker off) until PTO. I've noticed some behavior with charging my Model S and was wondering if this was normal

• If I leave the vehicle plugged into the Tesla Wall Connector (V2) and the vehicle is fully charged (80%), once the PW battery drains to 50% (typically gets this low overnight for house loads), if the car tries to charge (probably due to vampire drain), it will stop charging and charge port will turn red. There is no reason for the failure in the app other than charging stopped, but if I try again while observing the messages in the car, a message appears that the vehicle will not charge due to Powerwall level.
• Another observation is that if I charge during the day while I have PV production, the vehicle will charge at full 40A. At this point, power is being pulled from both PV and PW. However, once the PW reaches 75% SOC, the charge rate steps down to 24A in the vehicle to match the current PV production of approx 6.9kW.

It should be noted that the PW use is set to Self-powered with 5% reserve ... this will be changed to Time based control once I have PTO. Is this normal behavior? I realize that the grid is off which is not typical and will be powered back on once PTO is granted, but was wondering if this sort of negotiation between PV, PW and charging is expected.

Thanks!!!

 

[1100MCM]

It looks like it’s doing exactly what it’s supposed to be doing considering you’re off grid.

 

[jjrandorin]

what does it say in your tesla app when you access the powerwalls and check:

Customize -- Vehicle charging during power outage (what percent do you have there)?

 

[Tim-in-CA]

what does it say in your tesla app when you access the powerwalls and check:

Customize -- Vehicle charging during power outage (what percent do you have there)?

Doh! LOL ... I guess I should have scrolled ALL THE WAY down! It is set to 75%! So I guess it is doing exactly as expected. I wanted to take advantage of the unused generation that is NOT going to the grid to charge the vehicle. So I see that with this setting I can adjust this threshold. Good to know once I can turn on the main breaker once SCE gives me PTO.

 

[Tim-in-CA]

I guess my only issue is that the car gets into a permanent charge failure state even when PW conditions are above the threshold. My only recourse is to unplug and replug in the vehicle to start charging again. Pressing Start charging in the app will not work. From the video on the learn more section of customize, it should be automatic.

 

[jjrandorin]

Doh! LOL ... I guess I should have scrolled ALL THE WAY down! It is set to 75%! So I guess it is doing exactly as expected. I wanted to take advantage of the unused generation that is NOT going to the grid to charge the vehicle. So I see that with this setting I can adjust this threshold. Good to know once I can turn on the main breaker once SCE gives me PTO.

That setting there only takes effect when there is no grid. A lot of us wish there was some way to have it take effect when there IS grid, but right now it doesnt do anything unless you are in a grid out situation.

Its a good way to dump extra electricity into your EV in a grid outage situation, instead of the PV just being cycled off, if there is extra generation like there would likely be right now.

 

[dc81]

I just wish there was a way to dump excess (once PW is full) to the car rather than back to the grid.

 

[Tim-in-CA]

I just wish there was a way to dump excess (once PW is full) to the car rather than back to the grid.

Yea, as mentioned, this behavior seems to be only applicable when off grid. Agree, it would be better to prioritize vehicle charging over dumping back to the grid then pulling it back to charge the vehicle as there are efficiencies lost in both directions. Hopefully there will be a future FW update to allow for more control