Could Stormwatch have somehow increased my Powerwall capacity?

[JakiChan]

During the recent storms here in NorCal we had a few Storm Watch events and I put my Powerwalls on 100% backup. Now that weather is back to normal I put things back to my usual settings: 40% reserve. But I'm noticing that overnight my Powerwalls aren't discharging as much as they used to. It used to be they'd get as low as 42% or 41% but every since the recent storms they're at 50%+ when I wake up.

We're not using grid power, and there's not be any increase in home usage per either the Tesla app or the Span app. It's like the Powerwalls "found" and extra 10% of capacity.

 

[jjrandorin]

During the recent storms here in NorCal we had a few Storm Watch events and I put my Powerwalls on 100% backup. Now that weather is back to normal I put things back to my usual settings: 40% reserve. But I'm noticing that overnight my Powerwalls aren't discharging as much as they used to. It used to be they'd get as low as 42% or 41% but every since the recent storms they're at 50%+ when I wake up.

We're not using grid power, and there's not be any increase in home usage per either the Tesla app or the Span app. It's like the Powerwalls "found" and extra 10% of capacity.

The days are progressively getting longer (winter solstice was dec 21 2022. Every day past that day, given exact same weather conditions, will generate slightly more power.

 

[JakiChan]

The days are progressively getting longer (winter solstice was dec 21 2022. Every day past that day, given exact same weather conditions, will generate slightly more power.

That's not quite the point. We're talking about overnight draw. Not about solar production. My batteries get up to 100% every day.

 

[jjrandorin]

Gotcha.

You mention your normal 40% reserve. Are you using self powered mode or time based controls? Im only asking because, its unlikely to be a battery cell balancing type thing, since you mention it charges to 100% daily. Perhaps there is a difference in buffer? Did you get any firmware updates or anything?

 

[zanary]

Yes. When on StormWatch, 100% is actually 100% and will always show 100%, however for day 2 day use, when it shows 100%, it more like 90 something percent, however shows 100%. I think this is documented somewhere on the Powerwall/Solar support site on Tesla.com.

It's like how they recommend never charge your Tesla up to 100% unless you really need to, and normally charge up to 90%. The only difference is that it always shown 100% for the powerwalls regardless of daily charge or when StormWatch is activated.

 

[jjrandorin]

Yes. When on StormWatch, 100% is actually 100% and will always show 100%, however for day 2 day use, when it shows 100%, it more like 90 something percent, however shows 100%. I think this is documented somewhere on the Powerwall/Solar support site on Tesla.com.

It's like how they recommend never charge your Tesla up to 100% unless you really need to, and normally charge up to 90%. The only difference is that it always shown 100% for the powerwalls regardless of daily charge or when StormWatch is activated.

But it doesnt, though, at least for me. My system has been in stormwatch mode for 2 days now (as of today 1/23/2023) and it originally was at 100% from solar, stormwatch activated, and is now hovering at 97-98% shown in the app.

 

[zanary]

I don't think it will leave it at 100% for an extended period of time. I've seen mine also drop down to 95% under storm watch, and fully charge up to 100% from grid a few hours later. There was an article on the Tesla support site that spoke of StormWatch. I just don't have the link from year ago, but I did a quick search, and I found this link for StormWatch: Storm Watch | Tesla Support

They mention it in the detail they did years ago, but you can interpret the section under Enabling Stormwatch. FULL = 100 of the total capacity and not the daily 100% full. I guess one could also interpret it differently as well. I wish I had the old text saved where they provided the percentages.

Your system will continue to operate as normal, and your Powerwall will automatically react to severe weather events that may cause a grid outage. When Storm Watch mode activates due to a severe weather event in your area, Powerwall charges to full, protecting you against outages.

 

[jjrandorin]

I don't think it will leave it at 100% for an extended period of time. I've seen mine also drop down to 95% under storm watch, and fully charge up to 100% from grid a few hours later. There was an article on the Tesla support site that spoke of StormWatch. I just don't have the link from year ago, but I did a quick search, and I found this link for StormWatch: Storm Watch | Tesla Support

They mention it in the detail they did years ago, but you can interpret the section under Enabling Stormwatch. FULL = 100 of the total capacity and not the daily 100% full. I guess one could also interpret it differently as well. I wish I had the old text saved where they provided the percentages.

Your system will continue to operate as normal, and your Powerwall will automatically react to severe weather events that may cause a grid outage. When Storm Watch mode activates due to a severe weather event in your area, Powerwall charges to full, protecting you against outages.

That makes sense (perhaps 100% full includes the buffer in stormwatch mode and does not in regular operation).

My two powerwalls currently have a total pack energy value of >29kW (when added together) but I think that 100% in the app does not include all of that buffer above 13.5kW each. I know for a fact that 0 in the app is about 4-5%, but am not sure about top buffer. That would make sense though, if stormwatch enabled "it all" but then did not let it charge all the way up for more than X period of time.

Speculation but matches what is going on in my tesla app right now.

 

[JakiChan]

You mention your normal 40% reserve. Are you using self powered mode or time based controls? Im only asking because, its unlikely to be a battery cell balancing type thing, since you mention it charges to 100% daily. Perhaps there is a difference in buffer? Did you get any firmware updates or anything?

Self-powered. I've been on self-powered ever since install, with the reserve setting at 40%. And, at time of install (October) the lowest the battery would get would be like 41% or so overnight before being recharged by solar.

I can't account for the battery only getting down to low 50s by the power usage, since the 24-hour usage numbers are still just about the same. Kinda weird.

 

[Evans]

The days are progressively getting longer

I think this might be partly the reason you are draining your powerwall less. You are likely using power from solar longer before using the powerwall.

 

[Zinc_Saucier]

That's not quite the point. We're talking about overnight draw. Not about solar production. My batteries get up to 100% every day.

Do you use your batteries during the day too? If not, just tap on the Powerwall icon in the app and see how much energy was discharged.

 

[cwied]

My 2018 vintage Powerwalls neither charged above regular 100% in Stormwatch nor showed any change in maximum charge (as reported by the API) after charging in Stormwatch during the last storm. I do see minor differences in maximum charge depending on depth of discharge. I normally run TBC with export everything and a 33% reserve. If I change this to a 20% reserve I notice a decrease in the reported full capacity.

 

[dailo]

Self-powered. I've been on self-powered ever since install, with the reserve setting at 40%. And, at time of install (October) the lowest the battery would get would be like 41% or so overnight before being recharged by solar.

I can't account for the battery only getting down to low 50s by the power usage, since the 24-hour usage numbers are still just about the same. Kinda weird.

I am noticing the same thing, but mainly because my PW doesn’t have to start discharging until a little later everyday as the days are getting longer. Before I would start discharging before 3PM but now it it can get closer to 4PM before it starts to discharge so it doesn’t use as much.