Solar + Powerwall: Lights have started flickering when off-grid

[Yonki]

Had a 12kW Solar/3 Powerwall/2x SolarEdge Inverter system installed 2 weeks ago. Haven't received PTO, but 1 week ago I discovered that, even as overcast as it's been here, I'm making and storing enough power to go off-grid 24/7. So we've been PG&E-free for a week. Everything's been working fine.

But this morning I noticed that the lights in one of our bathrooms was flickering. Checked and all of the built-in lights in our house are flickering. House is 2-3 years old; all the lights are some kind of embedded LED.

Wondering if anyone has an idea what might have changed and/or what is causing the flicker? Voltage is steady at 118V. Frequency fluctuates between 59.5Hz and 59.9Hz (all our kitchen clocks are losing something like half an hour a week . Waveform isn't a perfect sine-wave, but it's not terrible (see below). Amplitude does seem to jump up and down about 1%...maybe our lights are sensitive to that small a variation? This would be easier to understand/accept if the lights were flickering since day 1, but this happened after about a week of no-flickering...

Curious if anyone has run into this before?

 

[gpez]

You checked all of the things I would off the bat: voltage, frequency, and waveform. Curious to hear if you figure it out.

My house is similar and our master bedroom closet and master bathroom LED lights flicker like crazy when on utility power. Only the lights in those rooms, and the flickering varies in intensity for reasons I can't figure out despite months of troubleshooting. Same light bulbs in other fixtures in the house have no problems. If you figure out what's going on please do share!

(Maybe I need to pick up a DS1054...)

 

[Yonki]

You checked all of the things I would off the bat: voltage, frequency, and waveform. Curious to hear if you figure it out.

Will definitely post if I figure it out.

(Maybe I need to pick up a DS1054...)

I recommend it! Not Tektronix but good enough for almost everything I need to do! Replaced this enormous heavy thing with higher bandwidth and so many more features!

 

[aesculus]

So we've been PG&E-free for a week. Everything's been working fine.

What are your specs like when you go back on PG&E?

 

[Yonki]

What are your specs like when you go back on PG&E?

Good question - I'll check that out when the scope's free again.

I did do some experimenting. For my own reference, I'm numbering my Powerwalls 1 - 3 when looking at them from outside.

• Disabled both solar inverters: still heavy flickering (it's actually gotten worse since this morning)
• Running house on Powerwall #3 only: same heavy flickering
• Running house on Powerwall #2 only: very light flickering - this is probably what it looked like for the first 6 days - you really have to look for flicker to see it.
• Running house on Powerwall #1 only: couldn't get system to switch to off-grid mode. I think the Gateway got a little confused with all these Powerwalls disappearing and reappearing. I toggled the Powerwall power switches while I was running on grid power, give it a few minutes for the Gateway to figure out what's what, then request off-grid operation. In a few hours when I wouldn't mind if I lost power to the whole house I'm going to reset the Gateway (and the Powerwalls) and try again.

Anyway, I've seen enough to make me suspect Powerwall #3.

Does anyone know if under light load (<1kW) conditions, the load is shared amongst the 3 Powerwalls or if it's just one Powerwall supplying all the power?

 

[DrSmile]

I never considered that the inverters on Powerwalls could go bad. Duh for me! Considering I have already had to replace my solar inverter after 2 years that makes me worry.

 

[Yonki]

Well this morning all three Powerwalls are back on, and there’s no flickering. So it’s either an intermittent problem or Powerwall 1 or 2 is now powering the house while 3 takes a break.

There’s clearly more experimenting to do…

 

[gpez]

Well this morning all three Powerwalls are back on, and there’s no flickering. So it’s either an intermittent problem or Powerwall 1 or 2 is now powering the house while 3 takes a break.

There’s clearly more experimenting to do…

Any difference in the AC waveform?

 

[Yonki]

Any difference in the AC waveform?

Yes! Both still about 118.5 Vrms, but one certainly looks less noisy than the other:

Flickering:​

Not Flickering:​

Waveform is the same, but there's a lot less...crap? Jitter? Less frequency variation, possibly less amplitude variation - not sure why it seems less "thick" - I'm pretty sure scope is set to the exact same settings.

Notably the flickering one is bouncing around between 59.2 and 59.9 Hz, while the clean one is between 59.9 and 60.2 Hz, so when running off the "good" Powerwall/inverter, maybe my clocks won't be running so slow (we've been losing 8 or 10 minutes a day).

 

[aesculus]

Notably the flickering one is bouncing around between 59.2 and 59.9 Hz, while the clean one is between 59.9 and 60.2 Hz, so when running off the "good" Powerwall/inverter, maybe my clocks won't be running so slow (we've been losing 8 or 10 minutes a day).

That's close to the math I am seeing since a solid .4 Hz would cause you to loose 10 minutes in a day clock duration. Yours varies of course so not solid .4 Hz but average. Your worse case is .8 Hz loss and never getting to 60 Hz. Your good one averages about 0 loss.

 

[CrazyRabbit]

check the harmonics...

 

[yblaser]

Anyone know how the system syncs with the line frequency and phase on and off grid especially with multiple powerwalls? Reading some of the online documentation the gateway might have some role but I don't know exactly how that works. Is there some communication over the CAN bus or do the power walls just sense the line conditions and synchronize?

 

[Yonki]

check the harmonics...

That's a good idea. Right now I'm looking at the power line through a 120V - 12V transformer, that could potentially be introducing harmonic distortion. Tomorrow I'm getting an isolation transformer so I can isolate my scope from the 120V power - once I do that I can directly monitor the power line, then I'll turn on the FFT and see what's there...

 

[BGbreeder]

That's a good idea. Right now I'm looking at the power line through a 120V - 12V transformer, that could potentially be introducing harmonic distortion. Tomorrow I'm getting an isolation transformer so I can isolate my scope from the 120V power - once I do that I can directly monitor the power line, then I'll turn on the FFT and see what's there...

If was looking for harmonics, I would prefer to use high voltage probes rather than a transformer, which is an inductor, and can both generate and remove harmonics.

All the best,

BG

 

[Yonki]

If was looking for harmonics, I would prefer to use high voltage probes rather than a transformer, which is an inductor, and can both generate and remove harmonics.

All the best,

BG

That’s exactly what I said (or at least tried to say) I was going to do.

 

[Flick75]

Tomorrow I'm getting an isolation transformer so I can isolate my scope from the 120V power

If was looking for harmonics, I would prefer to use high voltage probes rather than a transformer, which is an inductor, and can both generate and remove harmonics.

That’s exactly what I said (or at least tried to say) I was going to do.

That's not even close to exactly what you said. You said you were going to use an isolation transformer. @BGbreeder recommended high voltage probes. Not an exactly at all or even tried to say.

 

[Yonki]

I’m getting an isolation transformer to isolate the oscilloscope from the 120V line so I can then directly probe the 120V without potentially shorting the oscilloscope’s ground to hot (or even neutral which probably wouldn’t blow anything up but would likely introduce noise & ground loop issues).

The confusion seems to stem from the fact that you can use isolation transformers

1. on the signal you are measuring, or
2. on the power supply of the oscilloscope so the scope is isolated from the 120V line

#2 is best, but I was initially doing #1, because I didn’t have an isolation transformer for the power supply to the scope. Since using a transformer on the signal can itself distort the signal, I announced my intention to get a proper 300VA isolation transformer so I could measure the signal (the line voltage in my house) directly (#2).

As far as high voltage probes go, tomorrow I will check if my existing probes/scope can directly handle 120V or if I’ll need to add a ~90M resistor to divide down the signal by another factor of 10.

 

[Flick75]

I’m getting an isolation transformer to isolate the oscilloscope from the 120V line so I can then directly probe the 120V without potentially shorting the oscilloscope’s ground to hot (or even neutral which probably wouldn’t blow anything up but would likely introduce noise & ground loop issues).

The confusion seems to stem from the fact that you can use isolation transformers

1. on the signal you are measuring, or
2. on the power supply of the oscilloscope so the scope is isolated from the 120V line

#2 is best, but I was initially doing #1, because I didn’t have an isolation transformer for the power supply to the scope. Since using a transformer on the signal can itself distort the signal, I announced my intention to get a proper 300VA isolation transformer so I could measure the signal (the line voltage in my house) directly (#2).

As far as high voltage probes go, tomorrow I will check if my existing probes/scope can directly handle 120V or if I’ll need to add a ~90M resistor to divide down the signal by another factor of 10.

Curious if anyone has run into this before?

It's interesting that you're inquiring if anyone else on this forum has run in to this before based on your technical expertise on the subject already. I personally believe that most people, minus the responders in this thread, have a hard time comprehending what you're trying to diagnose.

 

[Yonki]

It's interesting that you're inquiring if anyone else on this forum has run in to this before based on your technical expertise on the subject already. I personally believe that most people, minus the responders in this thread, have a hard time comprehending what you're trying to diagnose.

I don’t expect expect anyone to understand exactly why this problem is occurring (though it would be great if someone did), I’m just asking if anyone else had seen the lights in their house flickering like crazy when they were running off Powerwall(s). Believe me, you don't need to be an electrical engineer to recognize there’s a problem - any sighted person would notice the flickering I’m seeing!

And then if someone had run into this, they might be able to tell me how Tesla responded, etc., which might help me get Tesla to address this with a minimum of effort and misunderstandings.

Since the problem is intermittent (and thus guaranteed not to be present when Tesla shows up to look at it), and I seem to be the first person who’s run into it, I’m sharing how I’m going about troubleshooting & documenting it in case someone else runs into this problem later. It’s also nice to have the help of a few other experts on this forum in case I miss anything.

The big picture (so far) for non-technical flowers of this thread is that a marginal Powerwall can be functioning yet make many of the LED lights in your house flicker like crazy, like “there should be a seizure warning on this” crazy and “my wife will never put up with this” crazy. In a few weeks or months I should be able to post what Tesla did or didn’t do to address it.

 

[slcasner]

@Yonki, if it is any consolation, I understood right away what you meant when you said you needed to get an isolation transformer. I faced the same problem when diagnosing a Sony TV from 1980s where the internal ground was connected to the hot side of AC power! For anyone unfamiliar with using an oscilloscope, if I had attempted to connect the scope's ground clip to a ground point in the TV circuit in the usual manner without plugging the TV or the oscilloscope into an isolation transformer it would have immediately shorted out the 120V power at the full current capacity of the circuit, causing a big spark and probably burning up part of the TV circuit or the 'scope or probe.