Outage yesterday, surprising battery charge "lost"

[WSE51]

In my part of Los Angeles there was a 2 hour outage yesterday due to a big rain storm. No problems with the Powerwalls kicking in. I got a notification that they were delivering power and were at 100% charge. 2 hours later the power returned, my 4 Powerwalls were shown at 54% capacity.

Assuming 13.5 usable kWh per Powerwall, that should mean about 25 kWh was discharged: 4 times 13.5 times 46%.

But the Tesla app shows that the Powerwalls only delivered 14 kWh during the outage. I could eyeball this by looking at the graph showing about 7 kW home usage during the 2 hour blackout, and I confirmed it by downloading the stats which Tesla provides for every 5 minutes.

Disappointing, implies Powerwalls would have fully drained in 4 hours and nowhere near the 54 kWh total capacity I expected.

I called into Tesla Powerwall support to ask why nearly half the lost charge was not delivered. They are researching.

Anyone else had this experience?

 

[Icebox_inel]

Can you add the graph for the day?

 

[garrett5688]

I have a tangential question - did you actually get an app notification of your grid outage? Many here (myself included) are not getting them for some reason

 

[Icebox_inel]

I have a tangential question - did you actually get an app notification of your grid outage? Many here (myself included) are not getting them for some reason

Notifications are a bit unpredictable, it depends on several factors such as, if the battery is connected to the home internet and if the home internet service is lost when the power goes out. The truth is that tesla has been working on this issue for a long time and as they make improvements to the software they improve the notifications.

 

[macbeth]

In my part of Los Angeles there was a 2 hour outage yesterday due to a big rain storm. No problems with the Powerwalls kicking in. I got a notification that they were delivering power and were at 100% charge. 2 hours later the power returned, my 4 Powerwalls were shown at 54% capacity.

Assuming 13.5 usable kWh per Powerwall, that should mean about 25 kWh was discharged: 4 times 13.5 times 46%.

But the Tesla app shows that the Powerwalls only delivered 14 kWh during the outage. I could eyeball this by looking at the graph showing about 7 kW home usage during the 2 hour blackout, and I confirmed it by downloading the stats which Tesla provides for every 5 minutes.

Disappointing, implies Powerwalls would have fully drained in 4 hours and nowhere near the 54 kWh total capacity I expected.

I called into Tesla Powerwall support to ask why nearly half the lost charge was not delivered. They are researching.

Anyone else had this experience?

i posted earlier about the same issue, shorter outage, but I lost 7% in 5 minutes pulling 0.8kw from the powerwalls. Tesla is investigating my issue as well.

 

[wjgjr]

One thing that would be helpful is to note the battery charge percent and meter (energy imported/exported) numbers in the API right before and after a test outage (or to log it all generally.) The app itself includes reserves and may be doing other things that change the percentage from the true number. While it seems unlikely the difference is large enough to explain what was seen here, the API numbers would help rule out an app error and also get the true numbers for the amount of PW energy used.

 

[CrazyRabbit]

people who are experiencing this, do a off grid test with turning off solar and measure the battery capacity to zero.

my bet is battery calibration is off with newest firmware.

 

[CrazyRabbit]

i mean going from 100% to zero, measuring what was used.

 

[WSE51]

Thank you everyone for your replies. I was asked to upload the daily graph, and have attached it, along with a few other screenshots.

 

[WSE51]

Tesla got back to me today after studying my situation. They said that my Powerwalls were only supplying a little under 11 kWh instead of the theoretical max of 13.5 kWh (they also said they "reset" them and now they are at 11.8 kWh). Also the Powerwalls were only at 90% charge when the outage occurred. If I run the numbers using this information, the energy delivered from the PW is about 9% higher than the energy consumed by the house during the outage, and that difference would be due to the DC/AC conversion.

I'm surprised at the loss of capacity compared with the loss of capacity of my Tesla car batteries over time (which is in the 10% range after 5 years on a 2012 MS and a 2015 MS), but they said unless the loss is over 30% during the warranty period, they won't replace the batteries. I still have 6+ (or 8?) years to go on my warranty.