Off grid testing of new system batteries maxing out at 90%

[Electrph]

So I have been doing an extended off grid test over the long holiday weekend (new system / awaiting PTO) and everything has worked great just had one question (issue maybe).
Since I am off grid I understand solar cycles off when powerwall batteries are full since excess pv energy has nowhere to flow but my system is cycling off showing at around 89-90% battery capacity. Should it not normally allow batteries to charge closer to 100% before cycling off PV ?
I am viewing the status of system by connecting directly thru teg’s WiFi since system is still not showing on my tesla app but I assume this shows same / correct data since app gets info uploaded from powerwalls

 

[jrweiss98020]

Yes, they should charge to 98-100%. Have your installer check out the installation.

 

[BrettS]

How is your weather there and are the powerwalls installed outside? From my experience my inverters would cut out when my batteries reached about 98%, however there was another member who recently mentioned that he was seeing the frequency start to raise at around 90% as well. In that case people speculated that ambient temperature had something to do with it as the weather was getting colder and his powerwalls were installed outside. In my case my powerwalls are installed in my garage and my testing was done in the summer, so cold weather wasn’t a factor.

Unfortunately tesla doesn’t really publish any data about exactly how the system works and when and in what cases it will raise the line frequency to turn off the inverters, so all we have to go on is observation of how our systems behave.

 

[Electrph]

Thanks for reply’s,
I’m not sure I can bring up issue with Tesla (installer) yet as my system does not have PTO so may just raise questions from them haha But yea I will def bring up the issue if it continues after PTO and system operating with grid connected
I was thinking same @BrettS regarding weather. My powerwalls are in garage as well temp is dropping to about 60 F by 6AM in garage so not sure enough to be a factor.
Also could fact that yesterday was first full day of PV the system saw and therefore 1st opportunity for batteries to fully charge play a factor? Batteries balancing for first time? Just a thought

 

[jboy210]

When I tested mine I usually saw cycles from 95-97% peak down to 93-94%. I imagine it depends somewhat on how the inverter reacts to having the AC frequency increased to shut down inverter production.

 

[garrett5688]

I am viewing the status of system by connecting directly thru teg’s WiFi since system is still not showing on my tesla app but I assume this shows same / correct data since app gets info uploaded from powerwalls

I thought I had read somewhere that powerwall 100% isn’t really 100%, so the batteries don’t sit full for extended time, so maybe the TEG is showing true capacity?

Maybe @BrettS or someone has compared?

 

[Electrph]

I think the whole “true” 0% or 100% is issue whether it is a car or powerwall of battery management (powerwall or car electronics ) in that case would display 0% or 100% to user when in actuality has some reserve left for self protection or some capacity left for balancing etc. This I am seeing I think is more issue of teg deciding when to alter ac freq to shut down pv

 

[BrettS]

When I tested mine I usually saw cycles from 95-97% peak down to 93-94%. I imagine it depends somewhat on how the inverter reacts to having the AC frequency increased to shut down inverter production.

I spent a lot of time watching the AC frequency while I was operating off grid and in my case the frequency wouldn’t even start to raise until the powerwalls hit 98%. Up to 97% the frequency was always 60Hz, then shortly after they got to 98% it went up to 60.1Hz and as power continued to be fed to the powerwalls the frequency kept going up until it hit 60.5Hz and the inverters shut off.

But it certainly appears that there are some cases where the frequency starts to be raised sooner than 98%, however, in all cases with newer inverters they should cut off once the frequency hits 60.5Hz. It’s just a matter of figuring out why the TEG is raising the frequency early in some cases.

 

[BrettS]

I thought I had read somewhere that powerwall 100% isn’t really 100%, so the batteries don’t sit full for extended time, so maybe the TEG is showing true capacity?

Maybe @BrettS or someone has compared?

The TEG and the app definitely show SOC percentages, but the way they do it is very odd. There is almost no difference at higher SOC and there is a 5% difference when the batteries are nearly drained. For example at the low end the TEG will show the battery at 10% while the app shows 5%. In the middle the TEG will show 61% while the app shows 59% and then at the high end both the TEG and the app show 99%.

I don’t understand why they do this unless it’s to mask a bit of reserve held back at the bottom end. It is also my understanding that the reported 100% is not truly 100%, but both the TEG and the app report the same high SOC numbers.

 

[sorka]

I've done extensive off grid testing because I do not yet have PTO(Over two months already).

With firmware 1.50.1, I was able to charge up to 98% before the the PWs frequency rose to 60.4 Hz shutting the inverter off. So with 1.50.1, it was impossible to get above 98%.

With 1.50.2, the frequency rise above 60.4% in the low 80s resulting in lots of cycling. The inverter will cycle on and off and charge a little bit higher each time before shutting off again maxing out at around 90%.

At 90%, the inverter rises to over 60.4 Hz so fast that it can no longer incrementally charge the PWs so 90% is about as much as you can get while off grid.