Glad my car charger was not backed up

[aesculus]

When I did my PW design I purposefully excluded backing up my Wall Connector because my regular charging rate (about 18kW) and my capacity (26kWh) would overtax my PWs. So I left it on the grid side panel.

Last night my car was scheduled to charge at midnight and needed to be charged from 24% to 90%. This normally takes about 4 hours. At 12:09 we lost grid power (a car or tree took out our service area). Power was restored at about 4 AM. During that time the PWs worked flawlessly along with my UPS to protect a server. The only reason I knew this happened is that when I woke up at 6:30 I found some notifications on my phone for the two power events and the car charging event. I have audible alerts suspended on my phone for off hours thankfully.

My power draw during that time was fairly minimal (around 2kw) so there was no impact. I did not get close to my reserve setting.

The car however ran over my off peak period by 10 minutes since it got a late start. Oddly I tried multiple times using the app to stop the car charging and it said it did, but returning to the PW side, I could see it still charging. Then swiping back to the car side it naturally said is was charging.

Being a newbie I have a couple of questions:

1. What happens when you are running in non grid connected mode and energy draw depletes the PW to less than the reserve? Is the reserve really only for the Cost Savings mode not to discharge to the grid beyond that?
2. If number 1 is true how low will the PW's discharge to during a grid event?
3. A bit out of scope for this thread but any idea why the car would not stop charging via the app request?

 

[schrodarkian]

As to #3: I've had this happen multiple times with my M3. The workaround for me is that I discovered that if I cancelled charging, and then swiped off the M3 to say, the MS or the Powerwalls in the app, it will not start charging again. If I leave it on the M3, it would just start charging a moment or so after I stopped it. Definitely a bug.

 

[aesculus]

Maybe I waited (less than 15 seconds though) to long after the selection and swiping to the PW but that did not work for me on three attempts.

Probably just a bug that we will have to wait to have fixed. I am pretty sure in the past I have been able to stop it but not 100% if I was stopping a manual charge vs a scheduled charge. Maybe it was because the car was recovering from an error state. Not sure.

 

[jboy210]

My experience with the stop and then restart is that it occurs when I have a start time set and I interrupt it before charging reaches the set level. If I manually start charging the X or 3 and then terminate the charging, it stays terminated.

 

[cwied]

1. What happens when you are running in non grid connected mode and energy draw depletes the PW to less than the reserve? Is the reserve really only for the Cost Savings mode not to discharge to the grid beyond that?
2. If number 1 is true how low will the PW's discharge to during a grid event?
3. A bit out of scope for this thread but any idea why the car would not stop charging via the app request?

1. The backup reserve only applies when the grid is up. It's the reserve that you're saving to use when the grid is down (i.e., for backup purposes).
2. The PW's will discharge until they're "empty." In practice I think that means about 5% charge or so. Note that 5% charge shows up as 0% in the Tesla app. If the Powerwalls shut down due to low charge, they'll try to come up again every hour during daytime hours to see if there is enough solar production to charge. (see: Backup-Only | Tesla Support - look for "Powerwall at Low Charge").