Powerwall 2 - Outage “Switchover” Delays?

[Freakyguy666]

Due to multiple & frequent outages in my area, I decided to go with powerwall 2’s. Part of this decision vs a gas generator was due to the fact that I was promised that when the power from the utility was cut off (outage) the powerwall 2’s would kick-in within a few milliseconds and maintain my solar production (SolarEdge inverters) during the day time. However, I’m finding 2 issues:

a) at night (no solar) the switch from grid power to powerwall is more than a couple seconds. This is NOT a few milliseconds as was promised.

b) during the day, if/when an outage occurs, the solar inverters are reset and require several minutes to come back 100%.

We have the powerwalls configured to Backup Only mode.

Question: is this Normal? If so, why does Tesla advise “millisecond” switchover? if it’s not normal, what do you recommend as troubleshooting?

Thanks in advance!

 

[wjgjr]

For a), this is not normal in my experience. The switch should happen fast enough that at most you might have any UPS beep briefly and possibly see a flicker. Even our microwave clock, which loses power if you look at it wrong, doesn't have an issue. I have suggested before that when we lose power due to an issue with the electric (as opposed to us flipping a breaker) it sometimes takes a tiny bit longer, perhaps because Tesla first is monitoring an issue with the grid before deciding it needs to intervene. But even then, that is just when I get the UPS beep and flicker, vs. not noticing anything at all.

For b), this is the same behavior I see, and is likely because you, as I do, have your PWs in backup only mode. This means they are typically sitting in the 97%-99% range. So, when power goes out, PWs kick in. The problem is your PWs are full (from my testing, 98% = full,) so if you are generating more solar than your house is using at the time, the solar will immediately shut off because it has no place to send the excess energy. Once it shuts off, it seems the minimum interval before it will turn back on is 5 minutes. What I have actually seen is we lost power, and solar shut down immediately. We got the grid back in 5 minutes, and it took 10 minutes for solar to come back, probably because we did not have our A/C on, so the PWs had not drained below 98%. However, once the grid came on and we waited for the next 5-minute check, solar could resume because grid power was now available.

I would expect for b) that if your PWs were not full, solar should continue uninterrupted. I commented elsewhere, that I would probably prefer to set my PWs to backup-only, but with a ~90%-95% level instead, just to keep producing during minor outages, which seem more common. However, that is not an option in the app.

 

[jjrandorin]

Due to multiple & frequent outages in my area, I decided to go with powerwall 2’s. Part of this decision vs a gas generator was due to the fact that I was promised that when the power from the utility was cut off (outage) the powerwall 2’s would kick-in within a few milliseconds and maintain my solar production (SolarEdge inverters) during the day time. However, I’m finding 2 issues:

a) at night (no solar) the switch from grid power to powerwall is more than a couple seconds. This is NOT a few milliseconds as was promised.

b) during the day, if/when an outage occurs, the solar inverters are reset and require several minutes to come back 100%.

We have the powerwalls configured to Backup Only mode.

Question: is this Normal? If so, why does Tesla advise “millisecond” switchover? if it’s not normal, what do you recommend as troubleshooting?

Thanks in advance!

It shouldnt be a "couple of seconds". There is some switchover time, when you are running in backup only mode, or the powerwalls are not powering the home already (usually enough to have to reset a microwave clock or something) but it isnt "a couple seconds". Have you actually timed this and its "2 seconds" or are you saying that its 2 seconds because you have to reset your clocks?

Whether your clocks reset or not, at least in my limited testing, seems to have something to do with whether the powerwalls are already powering the home or not. In backup only mode, they are never powering the home. So, in backup only mode, I would expect there to be a slight lag time, enough to have to reset some clocks, etc, but certainly not 2 seconds.

On the second point, @wjgjr covered that. In backup only mode, your powerwalls are always "full" so if you have an outage, there is no where for the generated solar power to go, so the powerwalls shut them off. The PV wont come back on until the powerwalls drain some, down to 95-97%.

 

[BrettS]

Like the others have said, this definitely doesn’t sound normal. For a, for me the switchover is not totally seamless, but it’s definitely not “more than a couple of seconds”. It’s noticeable in that I can see the lights flicker for a fraction of a second, but that’s about it.

The only thing that I would think could potentially be an issue is exactly how the power fails. If it’s not just a clean shut off, the gateway needs to try to ride through certain minor problems. So it could be that if the power isn’t actually off, but also isn’t normal then it could take your gateway a little longer to respond and switch to the powerwalls.

There’s not really much troubleshooting that you can do, but I would be interested to see what happens if you try to simulate a power failure by turning off your service disconnect. That will be a clean shut off and the gateway should react pretty much instantly. You might still see a little flicker in the lights, but it certainly shouldn’t take seconds to react.

But either way, I think you’ll need to call tesla to see what’s going on for you.

 

[cridinger82]

the issue with pv during the day shutting off when pw's are at a high soc, is that the older inverters can't ramp the power up and down based on need... it either is on or off. The newer installs and the inverters that got newer firmware can "curtail" the voltage based on need. example

solar can produce 5kw.
house only needs 3kw and pw's are full.
solar ramps down to house needs therefore bypassing the need to use the pw's...

I haven't had mine installed yet but from what i've read is that the new inverters if setup properly will not shutdown if setup properly.

 

[BrettS]

the issue with pv during the day shutting off when pw's are at a high soc, is that the older inverters can't ramp the power up and down based on need... it either is on or off. The newer installs and the inverters that got newer firmware can "curtail" the voltage based on need. example

solar can produce 5kw.
house only needs 3kw and pw's are full.
solar ramps down to house needs therefore bypassing the need to use the pw's...

I haven't had mine installed yet but from what i've read is that the new inverters if setup properly will not shutdown if setup properly.

I believe that this is possible, however, I believe that in the OP’s case the inverters will still shut down when the system switches to backup power when the powerwalls are fully charged.

From my experience, when off grid the powerwalls will slowly ramp up the frequency as they approach a full charge. In my case when they hit 98% capacity the frequency will go up to about 60.2, then as they continue charging the frequency continues going up until it hits 62.5. So if the powerwalls are at 100% (which would be the case, since the OP is in backup only mode) then as soon as the system goes off grid the frequency will be raised to 62.5 and the inverters will shut down. Once the powerwall state of charge lowers a bit, then the frequency will come down and the inverters can start up again.

Now, that said, while it is possible to program the inverters to lower their output as the frequency raises, Tesla did not do this for my install (and it’s a new install... just over a month old). In my case, my inverters are configured to shut off when the frequency hits 60.5. So when I’m off grid my powerwalls will charge up to about 98.5%, the frequency will go up to 60.5 and my inverters will shut off. The house will run on the powerwalls until they get down to about 97%, then the inverters come back on until the powerwalls hit 98.5% again and it just cycles like this.

I am aware that it is possible for the inverters to ramp down, and I actually spent a little time trying to configure this on my own, but I wasn’t able to get it to work. In the end though, I decided that it doesn’t really matter as the net result is the same. In one case the inverters might spend 30 minutes on at 10kW and 30 minutes off, producing a total of 5kWh over that hour. In the other case the inverters would stay on for that hour, but be throttled back to 5kW, and they would still produce a total of 5kWh over that hour. There is going to be ‘wasted’ power either way.

 

[cridinger82]

I believe that this is possible, however, I believe that in the OP’s case the inverters will still shut down when the system switches to backup power when the powerwalls are fully charged.

From my experience, when off grid the powerwalls will slowly ramp up the frequency as they approach a full charge. In my case when they hit 98% capacity the frequency will go up to about 60.2, then as they continue charging the frequency continues going up until it hits 62.5. So if the powerwalls are at 100% (which would be the case, since the OP is in backup only mode) then as soon as the system goes off grid the frequency will be raised to 62.5 and the inverters will shut down. Once the powerwall state of charge lowers a bit, then the frequency will come down and the inverters can start up again.

Now, that said, while it is possible to program the inverters to lower their output as the frequency raises, Tesla did not do this for my install (and it’s a new install... just over a month old). In my case, my inverters are configured to shut off when the frequency hits 60.5. So when I’m off grid my powerwalls will charge up to about 98.5%, the frequency will go up to 60.5 and my inverters will shut off. The house will run on the powerwalls until they get down to about 97%, then the inverters come back on until the powerwalls hit 98.5% again and it just cycles like this.

I am aware that it is possible for the inverters to ramp down, and I actually spent a little time trying to configure this on my own, but I wasn’t able to get it to work. In the end though, I decided that it doesn’t really matter as the net result is the same. In one case the inverters might spend 30 minutes on at 10kW and 30 minutes off, producing a total of 5kWh over that hour. In the other case the inverters would stay on for that hour, but be throttled back to 5kW, and they would still produce a total of 5kWh over that hour. There is going to be ‘wasted’ power either way.

I would still like to assume that it is more stable for the pv system to continue to provide the load, rather then having to go back and forth from pw to pv and then back again... seems to be more elegant when the system ramps up and down based on need. Also allows the powerwalls to stay in full soc until pv falls below a reasonable level. i could be wrong...

 

[bkp_duke]

I can only comment from the standpoint of a "Self Powered" customer, but we've had 4 outages in 2.5 years since we have had our powerwalls, and every time the only reason we knew there was a power outage was either because the app showed us, or a neighbor called to ask if we still had power when they were out. The transition has been seamless every time.

 

[BrettS]

I would still like to assume that it is more stable for the pv system to continue to provide the load, rather then having to go back and forth from pw to pv and then back again... seems to be more elegant when the system ramps up and down based on need. Also allows the powerwalls to stay in full soc until pv falls below a reasonable level. i could be wrong...

It does seem to be more elegant, but I’m not sure that it’s really more or less stable. The powerwalls really won’t stay at a full SOC though, even if the inverters are configured to ramp down the powerwalls will hover around 98%, possibly going up or down slightly as the power demand of the house and the solar production amount changes. (The inverter ramping down works by reducing the output by a certain percent, so the inverter will still be providing more or less power depending on cloud coverage and such).

When the inverters are configured to cycle the powerwalls will go back and forth between 97% and 98%, so it’s really not much different.

 

[BrettS]

It’s worth noting that the whole ramping up and down thing is kind of an inexact science. It’s not like the gateway will tell the inverters, “Ok, the house is using 2.3kW, so only provide 2.3kW of power”.

Instead, when the inverters are providing more power than the house is using the excess will be sent to charge the powerwalls. As the powerwall SOC goes up it will raise the frequency which will tell the inverters to produce less power. If the SOC continues going up it ramps down the inverters even more. At some point it might reach an equilibrium where the inverters are producing exactly as much power as the house needs, but then your AC compressor might come on and the house will be demanding more power. It will then start drawing power from the powerwalls in addition to the reduced solar output which will cause the SOC to go down, which will cause the frequency to go down to tell the inverters to ramp up and produce more power. It might hit an equilibrium again, but then the sun might come out from behind the clouds and all of a sudden the inverters will be producing more power than the house is using, so the excess will charge the powerwalls again causing the SOC to go back up, which then causes the system to raise the frequency again to tell the inverters to ramp down.

 

[miimura]

Since the OP is using Backup Mode, there will be an interruption because the PWs are in Standby and they have to wake up and ramp up the power output to satisfy the house load. As someone said up-thread, if you are running in Self-Powered Mode there is no interruption because the system is already balancing the power demands of the house and the grid draw should be zero.

Since I run Time Based Control, the house is not always powered by PW and solar, so I retained all the UPS units that I already had on my computers and DVR to prevent them from rebooting when the power goes out.

 

[bob_p]

Since installing our system late last year, what we've seen:

• When power is disrupted briefly or goes out completely, it can take up to a couple of seconds (worst case) to get the TEG to switch over to powering the house. This delay is likely required for switching and to start generating the 60Hz sync replacement for the grid. During this time, lights will briefly flash, devices with processors will likely reboot (unless on a UPS).
  
  
• Immediately after grid power is lost, power is provided only by the PowerWalls. It will take several minutes before the TEG will begin accepting solar power. As long as the PowerWalls have some charge, this delay shouldn't have a significant impact.
  
  
• Once grid power is restored, the TEG will take several minutes before it decides to switch back to grid power.

We run our system in Self-Powered or Advanced/Cost Savings.

 

[BrettS]

Since the OP is using Backup Mode, there will be an interruption because the PWs are in Standby and they have to wake up and ramp up the power output to satisfy the house load.

I think we all understand that there will be an interruption, but what is being questioned here is the length of that interruption. The OP says that it is a delay of “more than a couple seconds” and that sounds excessive. In my experience the delay is just a fraction of a second and barely noticeable. Even when my PW’s are in standby and my house is not being powered by solar.

 

[miimura]

I think we all understand that there will be an interruption, but what is being questioned here is the length of that interruption. The OP says that it is a delay of “more than a couple seconds” and that sounds excessive. In my experience the delay is just a fraction of a second and barely noticeable. Even when my PW’s are in standby and my house is not being powered by solar.

Agreed. "A couple seconds" is not normal. Every interruption I have been home for has been less than one second.

 

[jjrandorin]

Agreed. "A couple seconds" is not normal. Every interruption I have been home for has been less than one second.

Thats been my experience as well, which is why I asked if the "2 seconds" was something the OP timed, or if it was basically hyperbole because they had to reset their clocks.

 

[jboy210]

Something is off. You should contact Tesla and have them check out your system. They, or you, should be able to turn off the grid power and in the house, you should see very little, if any, disruption of power.

 

[SSonnentag]

Our three Powerwalls run in backup mode. When the power goes out the cutover is so quick that our digital clocks don't even blink. I can see the LED lights in our house flicker, but that's it. The only other indication of a power outage is my computer UPS beeps a few times as it is quicker than the Powerwalls at catching power failures.

 

[JPP]

AS I recall once grid power is restored, there is up to a 5 minute delay before the solar inverters can frequency sync with grid power, and then they switch back on line. it is never 'instantaneous' but takes a few minutes.

 

[miimura]

AS I recall once grid power is restored, there is up to a 5 minute delay before the solar inverters can frequency sync with grid power, and then they switch back on line. it is never 'instantaneous' but takes a few minutes.

During this time, the Powerwalls are not only assessing the quality of the grid, but they are re-synchronizing the waveform so that they are aligned. There is never an interruption when the PWs rejoin the grid because of this synchronization.

 

[Freakyguy666]

Thanks so much for the feedback.

A couple more questions:

A) It sounds like there may be a slightly longer “cutover” when in Backup mode vs Self-powered.

If so, and assuming there were a Scheduled Outage by the utility starting in the morning (~8am) and ending in the late afternoon (~5pm), would it be advisable to switch over to Self-Powered say 20minutes in advance of the scheduled outage and then revert to backup mode once said outage is over?

B) Given the PV is being instructed to “Shut Off” when an outage occurs due to there not being sufficient excess capacity in the PWs to absorb the excess PV production, what would be expected to occur should the home be drawing the full production of the PV AND drawing from the grid (i.e. the home electricity demand is higher than the current PV output in this moment) when an outage occurs in backup mode?