Powerwall 2 + UPS Connundrum - and solution

[Kant.Ing]

Kanting, when I started this thread, I was on a much earlier version of the firmware (1.17?) which pushed the Hertz level to past 65 to stop the solar inverters from pulling power from the panels. Subsequent releases have lowered that value to 62.9-63.2 (in your case), which most UPSs can handle as 'good' power during that time frame.

When the power goes out, you should hear (if sound is implemented) the UPS beep that it is active for about a second or two as it provides cycles to those important loads until the PW2 inverter kicks in with its own cycles. Then the UPS simply matches cycles as best as possible and again passes through the PW2 power to those loads.

ALL my different UPSs work through this type of event with the PW2 now (I have many critical loads and 8 UPSs...) so you should be safe with whatever you choose.

Thank you for the update and opening the thread. Your info is helpful to me because I always want to provide a reliable power to my computers and don't want my file servers to lose power and end up corrupting data during such events. I will still keep an eye on this, since my UPS has spec'd an input 57-63Hz, and as this seems to be something Tesla firmware can touch, I hope it won't break in the future.

 

[abasile]

Just had chance to do this quick experiment by manually switching off grid. I found the frequency never exceeded 63.2Hz.

When the PW2 battery is at 100% and PV still producing, I opened the breaker, PW2 took over and the frequency of the PW2 output is 63.2Hz. It decreases gradually to 61.9Hz as PW2 discharges to 99%, and 60Hz when PW2 reaches 98%. I spent another hour monitoring their status, and I found my CyberPower CP1000PFCLCD never went into its battery backup mode and it continuously considered itself running on AC utility power (thanks to PW2).

The PW2 firmware is 1.32.0.

Approximately what was the ambient temperature when you performed this test?

 

[NinjaVece]

Thank you for the update and opening the thread. Your info is helpful to me because I always want to provide a reliable power to my computers and don't want my file servers to lose power and end up corrupting data during such events. I will still keep an eye on this, since my UPS has spec'd an input 57-63Hz, and as this seems to be something Tesla firmware can touch, I hope it won't break in the future.

Kanting, I happen to agree with you here. My wife and I run businesses out of our house - ten work stations for her and her folks and a few for my biz along with a couple of PCs dedicated to monitoring and information. Her systems need to stay up as they are VPN'd into anyone of two internet providers we have coming into the house (told you its a biz house) so are all behind UPSs. My systems are also behind UPSs. These are the APCs I've had for a long time that can handle 57-63 Hz.

But your concern that Tesla can change the Hertz level via firmware was also on my mind for my TRUE critical systems, which include the modems, two routers (I have separate routers from the provided modems), switches and two monster NASs (one main, one backup) I use for the businesses and as Plex servers for many folks that I absolutely do not want to hiccup in any way.

Thus the critical loads use an Eaton UPS that is rated (I think) all the way to 76 Hertz as to seeing 'good power'. If you have multiple loads throughout your house that would need a UPS, I highly recommend that your most critical be behind a UPS that has the widest range of Hertz functionality.

 

[Kant.Ing]

Approximately what was the ambient temperature when you performed this test?

I didn't specifically measure the temperatures, but for that warm Saturday afternoon I estimate the CyberPower UPS was at an ambient about 60F, and the Powerwall outdoor about 70F.

 

[abasile]

I didn't specifically measure the temperatures, but for that warm Saturday afternoon I estimate the CyberPower UPS was at an ambient about 60F, and the Powerwall outdoor about 70F.

OK, thanks. "Low temperature", i.e. 50F / 10C, is something that Tesla Energy level 2 support folks have blamed for the Powerwalls not lowering their frequency and accepting solar charging during grid outages. This was clearly not the case during your test. Our Powerwalls spend the great majority of their time, including early on sunny summer mornings, in cool to cold ambient temperatures so this is sort of important to me.

 

[Kant.Ing]

OK, thanks. "Low temperature", i.e. 50F / 10C, is something that Tesla Energy level 2 support folks have blamed for the Powerwalls not lowering their frequency and accepting solar charging during grid outages. This was clearly not the case during your test. Our Powerwalls spend the great majority of their time, including early on sunny summer mornings, in cool to cold ambient temperatures so this is sort of important to me.

Besides low temp, another condition to check is if the Powerwall output frequency can go even higher in Storm Watch mode when the battery potentially charges and uses its over-provisioning capacity, since the frequency so far seems to be a function of the battery SOC.

 

[bmah]

I did some off-grid testing on my Powerwall system and got some results I didn't understand: I turned off my grid connection, and observed the solar inverter turn back on after about five minutes and begin feeding the house and the batteries. After a couple hours of this, I declared victory and went out for lunch...I didn't really feel like leaving the system in the state it was in, so I flipped the grid connection back on before I left. During this time, the solar panels fed the house and charged the batteries up to about 98% (also back-feeding into the grid). When I came back, I said "cool, let's see if the Powerwall system will keep the inverter from starting". So I turned off the grid connection again. The Powerwalls started putting out power at 66Hz (according to the Powerwall API and a Kill-a-Watt). The solar inverter was definitely unhappy with this (so it didn't turn on, as expected), but so were a bunch of other things. My four UPSs stayed on battery because they didn't like the power (kind of expected this given the frequency...weirdly the two of them with control panels claimed the AC line frequency was 63 Hz, not 66 Hz). Some of the LED lights in my house flickered when they were turned on. Finally, my Insteon (home automation) system didn't work with the weird line frequency...it seemed that the Insteon devices depending on power line communication were just unable to do it. With so many things going wonky, I didn't keep things in this state for long before turning the grid connection back on (maybe 10 minutes?).

So. I'm confused about various devices giving different line frequency readings. Also I'm not sure what the Powerwall system should have done in this situation. I had concluded (by reading posts from @Kanting and @NinjaVece in this thread) that the Powerwalls should have kept the frequency at no greater than 63 Hz but (depending on who you believe) that might not have happened.

Any thoughts? Thanks.

Bruce.

PS. Firmware 1.34.3. Ambient temperature at the inverter and Powerwalls was probably about 65F. UPSs are a mixture of APC and Cyberpower, they were all indoors with an ambient temperature of around 70F.

 

[roblab]

I've had solar for 15 years, and battery backup. I have never had any problem with any electronics. Never. I have Powerwall 2 and still no problems.

Although your concern is laudable, I think most of the solar plus battery back-up systems don't have problems. I have heard this concern from others over the years, but it just doesn't seem to be as bad as you paint it.

 

[woferry]

Every APC/CyperPower UPS I dug up the specs for when I was looking (over a dozen) all indicated their support maxed-out at 63Hz. So they may simply not support reporting any value above that, and just call anything above 63Hz to be 63Hz. Personally, I'd trust the Kill-A-Watt and PW API more. Not sure if the solar inverter supports reporting the frequency on its display also, would be another place to check that is probably accurate since it uses it as a limiting/shutdown mechanism.

I'm sad to hear about Insteon not working, as I have lots of Insteon devices at my house. But honestly I'm about ready to give up on them, I've had several things die in the last year and the effort of re-creating all of the link databases just isn't something I've been looking forward to, so I've been hobbling along with a half-working system for a while now, and meaning to look for alternatives.

BTW, the previously-mentioned AmazonBasics UPS does have the frequency range in its manual, and it also indicates 63Hz max. In my research I've only found Eaton UPS's to claim support for above 63Hz.

 

[shs1]

I did some off-grid testing on my Powerwall system and got some results I didn't understand: I turned off my grid connection, and observed the solar inverter turn back on after about five minutes and begin feeding the house and the batteries. After a couple hours of this, I declared victory and went out for lunch...I didn't really feel like leaving the system in the state it was in, so I flipped the grid connection back on before I left. During this time, the solar panels fed the house and charged the batteries up to about 98% (also back-feeding into the grid). When I came back, I said "cool, let's see if the Powerwall system will keep the inverter from starting". So I turned off the grid connection again. The Powerwalls started putting out power at 66Hz (according to the Powerwall API and a Kill-a-Watt). The solar inverter was definitely unhappy with this (so it didn't turn on, as expected), but so were a bunch of other things. My four UPSs stayed on battery because they didn't like the power (kind of expected this given the frequency...weirdly the two of them with control panels claimed the AC line frequency was 63 Hz, not 66 Hz). Some of the LED lights in my house flickered when they were turned on. Finally, my Insteon (home automation) system didn't work with the weird line frequency...it seemed that the Insteon devices depending on power line communication were just unable to do it. With so many things going wonky, I didn't keep things in this state for long before turning the grid connection back on (maybe 10 minutes?).

So. I'm confused about various devices giving different line frequency readings. Also I'm not sure what the Powerwall system should have done in this situation. I had concluded (by reading posts from @Kanting and @NinjaVece in this thread) that the Powerwalls should have kept the frequency at no greater than 63 Hz but (depending on who you believe) that might not have happened.

Any thoughts? Thanks.

Bruce.

PS. Firmware 1.34.3. Ambient temperature at the inverter and Powerwalls was probably about 65F. UPSs are a mixture of APC and Cyberpower, they were all indoors with an ambient temperature of around 70F.

I have certainly reported a very similar experience when my Powerwall 2 puts out 66 Hz. Lots of things in the house beep and blink or stop working. I always shut down the PW2 as fast as I can now during a power failure and rely on my generator.

My understanding of Frequency Shift Power Control, the standard by which the PW2 is supposed to use to curtail solar production, is that if the frequency is 1 Hz above nominal, 60 going to 61 Hz in our cases, then the solar inverters are supposed to start to curtail output. By the time the frequency rises to 62 Hz, the solar output is supposed to be zero, but with the inverters standing by ready to provide power if the frequency drops. I saw this work well when I first installed the PW2. When the frequency goes to 66 Hz, however as it seems to more recently, that seems to signal the inverter to disconnect from the grid and so it is not available to power the house when needed, although it will typically try again every 5 minutes. Taking the frequency to 62 Hz is a polite way to say to the inverter, curtail your output, but be ready in case you are needed. Putting out 66 Hz is just rude and the inverters act accordingly.

 

[miimura]

Putting out 66 Hz is just rude and the inverters act accordingly.

I cannot think of a good reason for the Powewalls to output 66Hz unless it already tried 63Hz and there was still unwanted generation. It totally defeats the purpose of backup power. Anything that makes a UPS think the power is bad is itself inherently bad. Period.

 

[Frankman60]

What if electronic equipment in a home such as a router, computer, audio and video gear were plugged directly into an AC receptacle rather than a UPS device? When the grid goes down and the PWs provide power to the home at 63 to 66 Hz what does that do to the equIpment? Does the equipment keep on running or does it shut down, or worse get damaged?

 

[woferry]

I won't personally make any guarantees, but my opinion is that most (if not all) electronics should be fine. Just about anything electronic would be converting the AC to DC, and that conversion shouldn't care about the frequency at all. So anything with a wall-wart or silverbox-style supply should be just fine (it's why you sometimes see switches for voltage, but never frequency. If you saw something with a frequency switch then I'd be concerned).

Personally I'd be more concerned about things with AC motors, seems likely that the motor speed would be affected by the line frequency, and running 10% faster than expected might be a concern for something like a washing machine's spin cycle or things like that (maybe also vacuum cleaners, hair dryers, blenders, etc)? Maybe these things have some other sort of speed control (or are perhaps DC motors at this point, so maybe more of a problem for older appliances?), I'm really not certain.

Devices that use PLC (Power Line Communications, like Insteon devices mentioned above) are using the zero-crossings of the AC signal to send their data, so their operation can be affected by the change in frequency, but this shouldn't cause any damage, it might just stop working when the frequency is out of the expected range, worst-case it might require a power-cycle when things go back to normal, hopefully it would recover on its own.

 

[Frankman60]

I’m wondering why a UPS would or should be needed at all with PWs. I have a lot of UPS devices around my home, some are the more expensive sine wave type for picky equipment, and need to figure out what I am going to do soon. I looked at the specs on the UPS devices I have and all of them say they will support up to 63 Hz like others have posted. What’s the risk of not having any UPS backup devices if the home is equipped with Powerwalls? I don’t know for sure but I would guess that voltage spikes might be of concern but can’t that be addressed with a good surge suppressor?

I didn’t mention large LCD or OLED TV displays. Would they be able to handle 66 Hz power?

I won't personally make any guarantees, but my opinion is that most (if not all) electronics should be fine. Just about anything electronic would be converting the AC to DC, and that conversion shouldn't care about the frequency at all. So anything with a wall-wart or silverbox-style supply should be just fine (it's why you sometimes see switches for voltage, but never frequency. If you saw something with a frequency switch then I'd be concerned).

Personally I'd be more concerned about things with AC motors, seems likely that the motor speed would be affected by the line frequency, and running 10% faster than expected might be a concern for something like a washing machine's spin cycle or things like that (maybe also vacuum cleaners, hair dryers, blenders, etc)? Maybe these things have some other sort of speed control (or are perhaps DC motors at this point, so maybe more of a problem for older appliances?), I'm really not certain.

Devices that use PLC (Power Line Communications, like Insteon devices mentioned above) are using the zero-crossings of the AC signal to send their data, so their operation can be affected by the change in frequency, but this shouldn't cause any damage, it might just stop working when the frequency is out of the expected range, worst-case it might require a power-cycle when things go back to normal, hopefully it would recover on its own.

 

[miimura]

I’m wondering why a UPS would or should be needed at all with PWs. I have a lot of UPS devices around my home, some are the more expensive sine wave type for picky equipment, and need to figure out what I am going to do soon. I looked at the specs on the UPS devices I have and all of them say they will support up to 63 Hz like others have posted. What’s the risk of not having any UPS backup devices if the home is equipped with Powerwalls? I don’t know for sure but I would guess that voltage spikes might be of concern but can’t that be addressed with a good surge suppressor?

I didn’t mention large LCD or OLED TV displays. Would they be able to handle 66 Hz power?

UPS units are needed because the Powerwalls don't always pick up the load quickly enough. By my observations, if the Powerwall is discharging and the grid draw is approximately zero, then you will not notice the transition as the transfer switch isolates the house from the grid. However, if the Powerwall is charging from solar or is in Standby, it will take long enough to balance the load that many devices cannot ride through the transition.
Personally, I have three UPS units on these loads:
1. PC Server, 1000VA
2. Tivo DVR, 125VA
3. Office outlets (including desktop pc, printer, etc), Structured wiring box (inc. cable modem, router, ethernet switch, etc.), hallway can lights with LED bulbs, 1000VA
This setup was in place before the Powerwalls and I have kept them all in place because of the dropouts when the Powerwalls go into backup mode.

 

[woferry]

The Powerwall can't kick-in instantly, if it was already powering the house then a grid outage should be seamless, but if it was idle or charging the Gateway has to first disconnect the grid then enable the Powerwall, which may be only 10's (100's?) of milliseconds or such, but it's enough that some electronics might brown-out during the gap. From what others have said on this forum (I think even this thread) it seems that lights barely flicker, but more sensitive electronics might still reset, so UPSs were still needed for some things, though if it's the right UPS and immune to the PW's frequency tricks it's only needed for that brief moment.

I would expect that LCD/LED TVs are still DC devices (some even have external bricks these days), so I wouldn't expect them to have a problem, either.

 

[miimura]

During our last power outage my new LCD TV shut down and my Tivo Mini device rebooted in the transition from grid to Powerwall operation. When the power comes back on, the Powerwall always does a good job of re-synchronizing the power before the switch reconnects the grid.

 

[Frankman60]

Well I guess I am going to need to buy some new Eaton UPS devices for my home with Powerwalls. I don’t see any other choice if I don’t want my Internet and Directv DVRs to restart during a grid outage.

About Insteon and X-10 powerline controlled devices. Some Insteon switches are dual band meaning that they support both powerline and radio frequency communication. Will a dual band Insteon wall switch be able to turn on the connected lighting load if the command is sent to the switch via RF from an Insteon RF hand held transmitter? I also have a lot of Insteon devices in my home, as well as some Apple Homekit devices that use either Bluetooth or WiFi communication. I suspect that the Homekit devices will continue to work at 66 Hz.

 

[woferry]

Well I guess I am going to need to buy some new Eaton UPS devices for my home with Powerwalls. I don’t see any other choice if I don’t want my Internet and Directv DVRs to restart during a grid outage.

I'm in a wait-and-see mode, as soon as I get PTO and have had a chance to charge-up the PW I'll be doing my own grid-outage-tests (i.e. flipping the main breaker). I have a hunch that lower-power things fed by wall-warts (like internet routers, Raspberry Pis, etc) just might ride-out the outage without the need for UPS's, but computers and my Dish DVR (and maybe my 3D printer) are likely a different story. APC also has an interesting UPS that goes between a 12V DC brick and a 12V DC device like some routers/etc (CP12142LI), that also shouldn't care about the grid frequency since it's purely DC. If my security cameras/DVR have any issues I might just get one or two of those for that application.

 

[eml2]

Just wondering if anyone tried shutting down the solar inverter when the grid was offline, but PW was pretty full and thus putting out 63 or 66 Hz. Will PW go back down to 60 Hz after a few mins since there is no more solar output (the inverter is off)?