Powerwall 2 + UPS Connundrum - and solution

[wbhokie]

I have a CyberPower 1500PFCLCD UPS connected to my desktop Dell PC. It's a Pure Sine Wave UPS that is needed for my PC's active power supply. There was one recent grid power outage that lasted for a minute in which my 2 Powerwalls took over powering the house but during the grid outage the UPS did switched over to its own battery to power my Dell PC before switching back to AC power.

I have a couple of those exact units and they went to their own battery until the Powerwalls reached a mid to low 90% charge and then adjusted their power frequency. Hence the whole discussion. But for me, they didn't work. I am likely going to switch to Eaton units and sell my existing Sine Wave units since they have a good resale value and are in high demand. I am still tempted to test the 600VA amazon basics model though.

 

[K-MTG]

Anyone try one of these? https://www.amazon.com/d/Computer-Ups/OPTI-UPS-SS1200-Stabilizer-Automatic-Regulator/B0007P11M4

Would it stabilize the frequency so we don’t have to replace our UPS

 

[miimura]

Anyone try one of these? https://www.amazon.com/d/Computer-Ups/OPTI-UPS-SS1200-Stabilizer-Automatic-Regulator/B0007P11M4

Would it stabilize the frequency so we don’t have to replace our UPS

It looks like that unit is only an AVR with surge protection. An AVR usually has a multi-tap transformer inside and it just selects the tap that is closest to the nominal voltage. Many good standby UPS units also have this function included to avoid battery use during low or high voltage periods.

If you intend to put this between a UPS and the wall outlet, I don't think it can do anything about the frequency - the waveform will just pass through.

The best solution for cleaning up the waveform in voltage and frequency is a double-conversion UPS. This type of UPS is always powering the loads with its own inverter while continuously charging the batteries from whatever AC power is available from the wall. This is very different from a standby UPS which normally passes through the AC power from the wall to the loads and only transfers the load to the battery powered inverter when the wall power is outside the configured limits.

 

[K-MTG]

It looks like that unit is only an AVR with surge protection. An AVR usually has a multi-tap transformer inside and it just selects the tap that is closest to the nominal voltage. Many good standby UPS units also have this function included to avoid battery use during low or high voltage periods.

If you intend to put this between a UPS and the wall outlet, I don't think it can do anything about the frequency - the waveform will just pass through.

The best solution for cleaning up the waveform in voltage and frequency is a double-conversion UPS. This type of UPS is always powering the loads with its own inverter while continuously charging the batteries from whatever AC power is available from the wall. This is very different from a standby UPS which normally passes through the AC power from the wall to the loads and only transfers the load to the battery powered inverter when the wall power is outside the configured limits.

Is there an affordable AC power failover solution? So we can have have a power strip with one outlet going to the UPS & the other for the wall. So if the UPS dies it will switch to the wall and then go back to the ups when it’s alive

 

[tjka4231]

I have a couple of those exact units and they went to their own battery until the Powerwalls reached a mid to low 90% charge and then adjusted their power frequency. Hence the whole discussion. But for me, they didn't work. I am likely going to switch to Eaton units and sell my existing Sine Wave units since they have a good resale value and are in high demand. I am still tempted to test the 600VA amazon basics model though.

In addition to my CyberPower UPS, I also recently purchased an Eaton 5P750 UPS for another desktop PC. The Eaton 5P750 is a Pure Sine Wave UPS. Good unit in spec with a wide input frequency range of 56.5 to 70 Hz that should handle well on switch overs to Powerwall when a grid outage occurs. But watch out for its noisy fan. Unlike the CyberPower UPS which runs silent, the fan in the Eaton runs all the time and is rather noisy, especially noticeable if it's in a quiet room near the PC. The fan runs even when there is no load on the UPS. The Eaton 5P750 has a noise rating of 45dB from the specs.

 

[tjka4231]

Did it switch over to the powerwall source? Or ran on its battery till grid power was restored?

My recent grid outage only lasted about one minute. During the grid outage, the CyberPower UPS was powering my PC from its internal battery until the grid power came back on in about one minute. The rest of the house was running off of the Powerwalls during that one minute grid outage.

 

[K-MTG]

In addition to my CyberPower UPS, I also recently purchased an Eaton 5P750 UPS for another desktop PC. The Eaton 5P750 is a Pure Sine Wave UPS. Good unit in spec with a wide input frequency range of 56.5 to 70 Hz that should handle well on switch overs to Powerwall when a grid outage occurs. But watch out for its noisy fan. Unlike the CyberPower UPS which runs silent, the fan in the Eaton runs all the time and is rather noisy, especially noticeable if it's in a quiet room near the PC. The fan runs even when there is no load on the UPS. The Eaton 5P750 has a noise rating of 45dB from the specs.

They are pretty pricey compared to the Cyberpower. But I suppose with the Powerwall you need a small capacity.

My recent grid outage only lasted about one minute. During the grid outage, the CyberPower UPS was powering my PC from its internal battery until the grid power came back on in about one minute. The rest of the house was running off of the Powerwalls during that one minute grid outage.

Was that the outage back on Jan 5. My power was out for like 4 minutes (I'm also in Irvine)

 

[tjka4231]

They are pretty pricey compared to the Cyberpower. But I suppose with the Powerwall you need a small capacity.



Was that the outage back on Jan 5. My power was out for like 4 minutes (I'm also in Irvine)

Yes, the Eaton UPS are more pricey than the CyberPower UPS. I believed the grid outage I experienced after my Powerwalls were installed occurred around the last weekend of January, either 26th or 27th.

 

[Frankman60]

I realize that this product is a little off topic, but do you think it could detect when Powerwalls take over during a grid outage? I mentions a setting for a milliseconds power interruption. I thought this product might be useful to know when a grid outage occurs, AND my phone is not receiving app push notifications because it is in Do Not Disturb mode (when I am sleeping). I believe that the Tesla app pushes a notification when there is a grid outage but it would not make it through an iPhone’s DND. Something like this could be used to alert the house occupants of a grid outage so actions could be taken to limit electricity consumption to preserve battery life (e.g. stop charging a Tesla).

https://www.amazon.com/dp/B005VDPE3...olid=33TEJ4DD9D20V&psc=0&ref_=lv_ov_lig_dp_it

 

[wbhokie]

I realize that this product is a little off topic, but do you think it could detect when Powerwalls take over during a grid outage? I mentions a setting for a milliseconds power interruption. I thought this product might be useful to know when a grid outage occurs, AND my phone is not receiving app push notifications because it is in Do Not Disturb mode (when I am sleeping). I believe that the Tesla app pushes a notification when there is a grid outage but it would not make it through an iPhone’s DND. Something like this could be used to alert the house occupants of a grid outage so actions could be taken to limit electricity consumption to preserve battery life (e.g. stop charging a Tesla).

https://www.amazon.com/dp/B005VDPE3...olid=33TEJ4DD9D20V&psc=0&ref_=lv_ov_lig_dp_it

I'm guessing it "could". I guess my inquiry would be more of the lines of why would you want to know at all? The time is too quick to physically take an action, and the tesla app itself still lists all backup events in its log, even if it is on DND mode. If it is just a millisecond power interruption, what is the benefit of the alarm? To tell you that you might need to turn some stuff on?

 

[Frankman60]

I'm guessing it "could". I guess my inquiry would be more of the lines of why would you want to know at all? The time is too quick to physically take an action, and the tesla app itself still lists all backup events in its log, even if it is on DND mode. If it is just a millisecond power interruption, what is the benefit of the alarm? To tell you that you might need to turn some stuff on?

Earlier in this thread we were discussing the possibility of a grid outage in the middle of the night when our EVs are charging. In total the electricity draw would be near 10 kW. If all circuits in the home are backed up by 2 or more PWs, they would be drained fairly quickly during a grid outage and possibly leaving the house with no electricity during the outage. My thoughts were if I knew that there was a grid outage, I would stop the cars from charging to preserve battery capacity to power the home until the grid came back up. If the grid outage occurred during the day, I would get the Tesla app notification real time (I hope) and I would unplug the EVs. But if my phone was in DND mode, I would not get the push notification. During the switch over from grid to PW I believe there is a several millisecond power interruption, which this device might detect and notify me by beeping. I would wake up and check the Tesla app to see if there is an event that just happened and I could unplug the EVs to preserve PW battery.

Correction: It was this thread where this was discussed: Is Telsa proposing the right thing for my Powerwall installation?

 

[wbhokie]

That makes more sense. Since I had 2 main panels I had the luxury of moving any breakers to a panel where that kind of scenario wouldn't happen. I even discussed moving my charger breaker to the backup and Tesla talked me out of it for that exact reason. But I can see how knowing would make sense in that case.

 

[cwied]

I'll just add a counter-argument to moving the charger out of the backed-up loads. The big advantage during the summer is that you can use the EV to soak up excess solar production to prevent the Gateway from shutting down the solar inverter as it gets full. If you don't do this, you may lose out on production that you could otherwise to drive around. For most short outages, this probably doesn't matter, but if there is a longer-term outage (e.g. earthquake for us out here), it might be nice to have the extra energy to be able to drive somewhere.

 

[Frankman60]

I'll just add a counter-argument to moving the charger out of the backed-up loads. The big advantage during the summer is that you can use the EV to soak up excess solar production to prevent the Gateway from shutting down the solar inverter as it gets full. If you don't do this, you may lose out on production that you could otherwise to drive around. For most short outages, this probably doesn't matter, but if there is a longer-term outage (e.g. earthquake for us out here), it might be nice to have the extra energy to be able to drive somewhere.

Good point. But in my case if there was a long term grid outage, I would need most of the PWs capacity to run my home each day. But we could charge our plug in EVs if there was any excess PW electricity.

 

[miimura]

Really, in a prolonged outage, the PWs are just a buffer. The key point is whether your solar is generating more than what you're using. If you have surplus generation, then you should be plugging in during the day while the solar is generating, even if it's only a 120V outlet.

 

[abasile]

I'll just add a counter-argument to moving the charger out of the backed-up loads. The big advantage during the summer is that you can use the EV to soak up excess solar production to prevent the Gateway from shutting down the solar inverter as it gets full. If you don't do this, you may lose out on production that you could otherwise to drive around. For most short outages, this probably doesn't matter, but if there is a longer-term outage (e.g. earthquake for us out here), it might be nice to have the extra energy to be able to drive somewhere.

During an outage, one might alternatively unplug an electric stove or dryer, then plug the car's Mobile Connector into that outlet. You might need a 240V extension cord to make that work, though. I happen to have a 20 foot NEMA 14-50 extension cord (that I've never needed to actually use).

We have a standard 120V outlet in our parking area, and it's on a backed up circuit. So we could use that to charge slowly if needed, as @miimura suggested.

Both of these options seem preferable to the possibility of a plugged-in EV totally draining the Powerwalls during a nighttime outage.

 

[cwied]

Fair enough. I personally chose the other way (backing up my 14-50) because I drive little enough that the charging would not drain my Powerwalls most nights. I do wish Tesla allowed the app to signal to stop charging so it wouldn't be an issue at all, though.

 

[wbhokie]

I'll just add a counter-argument to moving the charger out of the backed-up loads. The big advantage during the summer is that you can use the EV to soak up excess solar production to prevent the Gateway from shutting down the solar inverter as it gets full. If you don't do this, you may lose out on production that you could otherwise to drive around. For most short outages, this probably doesn't matter, but if there is a longer-term outage (e.g. earthquake for us out here), it might be nice to have the extra energy to be able to drive somewhere.

This initially was my argument. To be fair, we rarely, if ever, have power outages. You could argue that there was no real reason for me to even buy a powerwall in that case... some of it was more of the integration to a solar system in general to allow seemless transition during the smaller outages. I've lived in this same house now for 8 years. We only had a single outage that lasted more than 1 day that entire time. That is the only case that I would have even expended the battery completely. There have been many that were 6 hours or less, which the powerwalls would have covered. Dominion power is really good about fixing the power, especially where I am since our street is sort of a trunk hub... meaning if we lose power, so does all of of the branching neighborhoods, so a lot of people complain at the same time. A few other reasons I got powewalls were:

1) Our power company might change to TOU in the future and I wanted to have it already if they did.
2) I could claim the full tax credit this year
3) I got a $5,000 refund from Elon on my Model 3 (due to a price change) while ordering my solar. Put this toward a second powerwall.
4) I could include it in my solar loan now

Anyway, if I was in a more rural area, I would have had a NEMA outlet that I had the option of plugging the mobile charger into due to extended power loss on my backup powerwall breaker box, but I always have (at worst case) 170-200+ miles on my model 3 at the end of any given day and there are lots of other charging options around, so it isn't really needed for me.

 

[Kant.Ing]

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.

 

[NinjaVece]

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.

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.