during off grid test lost power to house with powerwalls still showing 10%

[Electrph]

was beginning another off grid pre-PTO test powerwalls started at about 28% .. so main breaker off simulate power out / turned on breaker to solar / turn on pv converter all night before .. batteries should have easily got me till dawn when i could produce from pv .. so just at sunrise power "shut down" to house .. i looked at teg flow (i do not have access to tesla app only teg's wifi ) batteries showed 10% / X thru grid cause off / zero pv production cause pre dawn but nothing flowing on diagram / fairly positive walls did not shut down due to load (nothing significant kicked on) system is set to "self consumption" with 33% reserve according to teg and i cannot change these.
So why would power walls stop providing power at around 10% showing on teg with no grid access / no pv production other than more load than they could provide? (again do not think this was case since nothing unusual running / did not have to reset power walls... i turned main breaker back on .. then later went back off grid same procedure batt at 12% and climbing from pv and worked fine again)

 

[jjrandorin]

I believe the percentages you see in the TEG directly will not match the ones you see in the app. I dont know what it is at the low end, but its possible that 10% on the TEG was 0 in the app. We know the powerwalls reserve power to be able to turn on when they receive power from the PV system.

Not sure what that value is though. Someone more knowledgable than me might be able to chime in on that.

 

[Electrph]

thank you... that was one of the plausible explanations I was thinking .. if this were the case though and powerwalls hit "0%" would they come back online once they started getting some pv energy or would they have needed to be reset with switch such as i believe is case when overloaded ?

 

[wjgjr]

I believe the percentages you see in the TEG directly will not match the ones you see in the app. I dont know what it is at the low end, but its possible that 10% on the TEG was 0 in the app. We know the powerwalls reserve power to be able to turn on when they receive power from the PV system.

Not sure what that value is though. Someone more knowledgable than me might be able to chime in on that.

10% in the teg corresponds to 5% (roughly - I haven't confirmed it is exact) in the app. This seems to be the point at which it shuts down to preserve the remaining charge.

 

[MorrisonHiker]

thank you... that was one of the plausible explanations I was thinking .. if this were the case though and powerwalls hit "0%" would they come back online once they started getting some pv energy or would they have needed to be reset with switch such as i believe is case when overloaded ?

From Best Practices During Power Outages | Tesla Support :

Running Low on Energy
If Powerwall has less than 10% energy remaining, it will enter a standby state. Powerwall will automatically attempt to recharge from solar for 6 minutes every hour between 8 am and 4 pm local time. If enough solar is available to charge Powerwall, it will remain on. Otherwise, it will wait for the next hour.

Restarting Powerwall
If your Powerwall system stops producing power, it may be in a standby state after running low on energy or after repeated overloads. To restart your system, switch off any energy-intensive loads to reduce the amount of power needed. You can initiate a restart with a quick toggle of the on/off switch on any Powerwall in your system. Remember that in order to maintain a connection to the Gateway, you must leave the Powerwall switch in the ON position.

A restart consumes some of Powerwall’s remaining stored energy. If energy is low and there is insufficient solar to charge, Powerwall will return to a standby state after 6 minutes, so it is best to initiate a restart during daylight hours.
​

We ran into this last year when we had a 48 hour outage and the Powerwalls hit 10% right before the sun came back up on on the second day. They tried throughout the day to bring solar back online but there was an issue and it kept raising the frequency and shutting solar back off after ~5 to ~35 minutes. A few days later, Tesla tweaked the firmware, our inverter firmware and adjusted the max frequency shut-off settings. We haven't been down to 10% since then so we don't know for certain if the issue would happen again.

 

[Electrph]

thank you all very much for the info makes me feel better system is functioning correctly

yet another reason i "need" access to app before PTO

And i also need to start reading more of the manuals .. i usually do but install happened short notice / excited to test off grid