Powerwall 2 + UPS Connundrum - and solution

[HankLloydRight]

For what it's worth, I have one PW2 without solar. I have an old APC UPS (with fresh lead-acid battery) on my HP PC and dual monitors, and a $50 "Amazon Basics" UPS on my cable modem and router. We've had a few outages recently and they all worked just fine to handle the faction-of-a-second during the switchover.

Does the PW2 change frequency when there's no solar inverters?

 

[jjrandorin]

For what it's worth, I have one PW2 without solar. I have an old APC UPS (with fresh lead-acid battery) on my HP PC and dual monitors, and a $50 "Amazon Basics" UPS on my cable modem and router. We've had a few outages recently and they all worked just fine to handle the faction-of-a-second during the switchover.

Does the PW2 change frequency when there's no solar inverters?

I dont know for a fact, but there would be no reason for it to change frequency without solar, since the reason it changes frequency is to shut off the solar.

 

[BrettS]

Does anyone know of any short-run-time (but reliable and long lived) capacitor-based UPSes that could provide just the few seconds of power needed when the gateway switches to Powerwall provided power? I hated my old lead-acid battery UPSes because they were so unreliable when the battery would get old and need replaced.

That would be an awesome solution for this use case, but I suspect that it is such a very limited use case that there’s not a market for such a product. I think most people want a UPS that, at a minimum, will last long enough to allow a computer to shut down cleanly, and ideally give it some additional runtime before that happens. I think trying to provide that amount of runtime with capacitors would get cost prohibitive pretty quickly.

I do agree about the issue with SLA batteries. They seem to last two or three years at best and unless you regularly test them (or just replace them on a schedule) you pretty much tend to discover that they’ve failed when the power fails and whatever they are ‘protecting’ gets shut down anyway.

I think the better solution here is lithium ion batteries for UPS’s as those last longer and can provide the runtime that people buy a UPS for. They are starting to be available in commercial UPS’s, like these, but they are way bigger and more expensive than one really wants to spend for home use:

Smart-UPS Single Phase Lithium-ion UPS

The only consumer grade lithium ion UPS I’ve found is this one, but it’s pretty tiny as UPS’s go:

APC Back-UPS Connect 50 Lithium Ion Network UPS, Mobile Power Bank 120V - APC USA

However, at the time I was searching it was before I had my powerwalls and I was looking for longer runtimes. I wonder if I should reconsider that UPS now that I have a powerwall, assuming it will handle my loads for at least a few minutes.

 

[eml2]

I simulated a power outage 2 weeks ago on a sunny day when my PW is at 100%. Since I haven't called Tesla to lower the frequency, its frequency jumped to 65 Hz as expected. I have 3 old UPSes, Only one of them had problem with the frequency. The ones that had no issue are Tripp Lite G1000U and Tripp Lite OmniVS1000. The one that had problem is Cyberpower (can't find the model #).

Note that this frequency issue only occurs when PW is full. Once PW dropped down to 98%, the frequency went back to 60 Hz.

 

[cali8484]

I have a Powerwall 2, and am disappointed to find that in the event of an outage it doesn't switch over fast enough to avoid a reboot of my Dell XPS desktop computer, cable modem and router. However, I assumed a UPS would take care of that issue, but understand from this thread that it may not. I have to say that my understanding of the issue discussed here is minimal as I am not technical. In any case, I haven't purchased one yet. Is there one in the $80 to $150 range that will avoid the issue that is discussed in this thread? I don't know what metric to look for in Ads. I only plan to plug in the three pieces of equipment listed earlier. Would one as basic as the CyberPower LE850G UPS Battery Backup with Surge Protection do the trick? If not, what would you recommend? Or would it be easier to just purchase that Surge Protector and request Tesla make the change discussed elsewhere in this thread.

Thank you very much in advance for recommendations and guidance.

You should be able to get Tesla to lower the frequency to work with the CyberPower UPS but depending on how critical your equipment is you may want to up your UPS budget a bit for UPS that provides clean power. The unit you mentioned provides modified sine wave power (i.e. not clean) which may or may not damage sensitive equipment over time depending on how often it's on. Based on various reports, it seems Powerwall can be quite sensitive and trigger grid switching on/off up to dozens of times a day so the UPS could be on quite often. Here is an example CyberPower model with similar power to the one you mentioned but provides clean power:

https://www.amazon.com/gp/product/B00429N18S/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1

You can also look at Eaton 5SC models that can tolerate wider frequency range.

 

[jrweiss98020]

You should be able to get Tesla to lower the frequency to work with the CyberPower UPS but depending on how critical your equipment is you may want to up your UPS budget a bit for UPS that provides clean power.
. . .

You can also look at Eaton 5SC models that can tolerate wider frequency range.

I think you do NOT want to have the UPS tolerate the higher freqs, if any equipment may be sensitive to the higher freq. The whole idea of the UPS is to shift to its conditioned power if the grid freq goes out of limits. I don't know how sensitive the PSU is to high freqs; my manual only says it's good for 50/60 Hz, the ATX12V standard says 47-63 Hz, and the 80Plus testing standard says +/- 1%.

 

[Cirrus MS100D]

It's interesting you mention the lithium ion based UPSes, I managed to buy this one ages ago because I have a rolling/raising desk that moves around a bit, so the UPS "had" to sit on the desk (various reasons) and this was the smallest UPS I could find:
APC Back-UPS Pro 500 Lithium Ion UPS - APC USA

Unfortunately it seems they discontinued it, though it certainly was very pricey compared to the standard SLA style. I wished they pursued these models as they (APC) rightfully touted 2x the service life of the batteries. [shrug]

 

[BrettS]

It's interesting you mention the lithium ion based UPSes, I managed to buy this one ages ago because I have a rolling/raising desk that moves around a bit, so the UPS "had" to sit on the desk (various reasons) and this was the smallest UPS I could find:
APC Back-UPS Pro 500 Lithium Ion UPS - APC USA

Unfortunately it seems they discontinued it, though it certainly was very pricey compared to the standard SLA style. I wished they pursued these models as they (APC) rightfully touted 2x the service life of the batteries. [shrug]

Wow, I didn’t even know that one existed. That looks like it would be perfect for this use. It’s too bad they discontinued it.

 

[HankLloydRight]

Maybe it's just me, but I think one thing needs a little clarification for any people just monitoring this thread.

When people with PW2+Solar mention their UPSs not working with the higher frequencies, that doesn't mean the UPSs stop supplying power to the downstream devices during an outage. It means that the UPSs stop accepting the wall power as "clean" and go into discharge mode for the duration of the grid outage (i.e. the normal UPS mode during an outage) and your downstream devices are only safe for as long as your UPS battery can last.

But correct me if I'm wrong, all these consumer UPSs, with or without the frequency change, will still handle powering the downstream devices for the split-second during the switchover to PW2 power. It's what happens after that that matters, and that's only if you have solar and the PW2 is at 100% and the inverters have to be shut off. Other than that one scenario, I don't think anyone needs to replace their existing UPSs if you just have a PW2.

 

[BrettS]

Yes, that is correct. The UPS will handle the switchover without problem. The problem is that when the powerwall is at 100% and it raises the frequency to shut off the inverters then the UPS will kick on until the frequency is back to normal. This could be several minutes. If it’s a bright and sunny day then this will keep happening as the solar tops off the powerwalls. At some point it’s likely that the UPS batteries will discharge completely and your UPS protected loads will shut down. This is because the UPS can’t recover and recharge it’s batteries during the few minutes that the frequency is low. Additionally the frequent battery cycling will lower the battery life in a standard SLA UPS.

 

[jjrandorin]

Maybe it's just me, but I think one thing needs a little clarification for any people just monitoring this thread.

When people with PW2+Solar mention their UPSs not working with the higher frequencies, that doesn't mean the UPSs stop supplying power to the downstream devices during an outage. It means that the UPSs stop accepting the wall power as "clean" and go into discharge mode for the duration of the grid outage (i.e. the normal UPS mode during an outage) and your downstream devices are only safe for as long as your UPS battery can last.

But correct me if I'm wrong, all these consumer UPSs, with or without the frequency change, will still handle powering the downstream devices for the split-second during the switchover to PW2 power. It's what happens after that that matters, and that's only if you have solar and the PW2 is at 100% and the inverters have to be shut off. Other than that one scenario, I don't think anyone needs to replace their existing UPSs if you just have a PW2.

As @BrettS said, thats correct, but as he also said, this could potentially happen several times a day during a power outage, depending on solar array size, number of powerwalls etc. In my own system, right now, my powerwalls fill from empty to full by 11:30 am to noon.

If I was in a power outage situation, without the frequency change, and older UPSs that dont tolerate the high frequency, what would happen is, Power outage in the morning (lets say), solar + powerwalls continue on as normal and fill batterys and run the home until 11:30 to 12 Noon, powerwalls reach 100%, powerwalls shut off solar by raising frequency... UPS complain and beep (*and any other symptoms such as microwaves, LED lights etc).

UPSs beep / continue to provide power until they run out or until powerwall drops back down to somewhere between 90-95%... when that happens, solar kicks back on. Sun still shining, starts providing power to powerwalls and powers home, powerwalls back to 100%... repeat.

Right now, My solar generates close to twice what I am using, especially since I am not driving much. My solar runs until about 7pm. With my current home load, in an outage, the solar would likely blip on and off several times in the afternoon as my powerwall drained from 100, and kicked the solar back on when it hit 95% (as an example) and filled back up.

So yeah, it only happens in that instance, but depending on number of powerwalls you have, and size of solar, "that instance" could be really common in a power outage with the sun up.

 

[RobbL]

@jjrandorin - I spoke with Tesla today and asked if they would lower the frequency. The agent I spoke with checked with level 2, who pushed back on making the change without knowing which UPS I had. But he will try to still make it happen. He did note that the current frequency on my Powerwall was 60 Hz. But I am assuming that without them setting a new upper limit, under certain circumstances it can go higher and that is when the problems ensue.

@cali8484 - Thanks for the recommendation for that other Cyberpower model. You are right, it isn't very much more and appears to my uneducated eyes to be significantly better than the one I mentioned. If Tesla insists on a model number I will give them that one.

Just to make sure I am understanding, when Tesla lowers the frequency, they are setting a new upper limit, lets say to 62.5 Hz. Once that is done, is there no set of circumstances under which I would have a problem with the UPS stepping in as soon as there was a break in power, and maintaining it until the Powerwall took over, a second or two later? Following that scenario, my understanding is that the Powerwall would then take care of providing power until it went to zero or the power was restored. In the meantime, during the day, my solar panels would be recharging the Powerwall at the same time that the Powerwall was providing power to the house, thereby extending the time before it went to zero and hopefully keeping us comfy until power was restored.

Thanks for the help and advice.

 

[jjrandorin]

@jjrandorin - I spoke with Tesla today and asked if they would lower the frequency. The agent I spoke with checked with level 2, who pushed back on making the change without knowing which UPS I had. But he will try to still make it happen. He did note that the current frequency on my Powerwall was 60 Hz. But I am assuming that without them setting a new upper limit, under certain circumstances it can go higher and that is when the problems ensue.

@cali8484 - Thanks for the recommendation for that other Cyberpower model. You are right, it isn't very much more and appears to my uneducated eyes to be significantly better than the one I mentioned. If Tesla insists on a model number I will give them that one.

Just to make sure I am understanding, when Tesla lowers the frequency, they are setting a new upper limit, lets say to 62.5 Hz. Once that is done, is there no set of circumstances under which I would have a problem with the UPS stepping in as soon as there was a break in power, and maintaining it until the Powerwall took over, a second or two later? Following that scenario, my understanding is that the Powerwall would then take care of providing power until it went to zero or the power was restored. In the meantime, during the day, my solar panels would be recharging the Powerwall at the same time that the Powerwall was providing power to the house, thereby extending the time before it went to zero and hopefully keeping us comfy until power was restored.

Thanks for the help and advice.

Yeah thats correct on frequency.

For the tesla rep, you needed to tell them you have cyber power UPS devices, and some of your LED lights flicker.

 

[RobbL]

So now the main question I have is why doesn't the Powerwall act like a $100 UPS when the power goes off and switch over fast enough to avoid any shut down of equipment it is supporting? Does it have to be that way or is it an oversight by Tesla that they will address with the Powerwall 3?

 

[jjrandorin]

So now the main question I have is why doesn't the Powerwall act like a $100 UPS when the power goes off and switch over fast enough to avoid any shut down of equipment it is supporting? Does it have to be that way or is it an oversight by Tesla that they will address with the Powerwall 3?

in my opinion this is not a powerwall thing, and is not something that tesla will "Fix" because it depends on which direction your power is flowing. Its the gateway that does the switching, and it takes "few microseconds" for the system to switch, depending on what is going on.

Sometimes, it will switch fast enough for almost everything (microwave clocks wont need to be reset, for example). Some electronics are sensitive to any power fluctuations, like computers, routers, etc.

A typical UPS is connected to the device it is protecting, where in the case of the powerwalls, there is the gateway in between, and the gateway has to figure out which direction the power is going (while a UPS just "provides power).

I dont think there is anything here for tesla to "fix", in my opinion.

 

[cali8484]

So now the main question I have is why doesn't the Powerwall act like a $100 UPS when the power goes off and switch over fast enough to avoid any shut down of equipment it is supporting? Does it have to be that way or is it an oversight by Tesla that they will address with the Powerwall 3?

It can certainly be done just look at the large data center UPS"s that can switch much more power than Powerwall without transient outage so the primary reason Tesla doesn't do it is likely cost concerns for a consumer grade product.

 

[BrettS]

I think that part of the problem is that there is solar generation going on as well. The utilities require sites that are generating solar power to conform to certain ride through regulations, meaning that even if there is a small glitch in the grid power the inverters will “ride through” it and keep generating. The concern is that if there is a minor glitch on the grid in the middle of the day and that caused all the solar generation sites to drop offline at the same time then it could turn a minor glitch into a major glitch as the other power generation sites suddenly have to recover from that huge instantaneous drop in production.

A dedicated UPS can react instantly to any tiny disturbance on the grid because it’s not part of a generation site, but the gateway can’t react the same way because it needs to follow the ride through regulations. The problem is that when a glitch does happen there no way of knowing if it’s just a tiny glitch that will be over in a micro second or the start of a large power outage. The UPS doesn’t care and it will switch to batteries immediately, but the gateway has to wait a fraction of a second longer to be sure that the power really is down or that the glitch is big enough that it doesn’t fall within the ride through guidelines. It can switch over at that point, but that fraction of a second can make a difference to some sensitive devices.

The response is also different depending on the state of your powerwalls at the time of the outage. If your solar system and/or powerwalls are already online and providing power to your house at the time of the grid outage, then the outage is usually pretty seamless. However, if the sun is down and the powerwalls are on standby then there’s another fraction of a second delay while the system gets the powerwalls online and ready to take over.

 

[HankLloydRight]

As @BrettS said, thats correct, but as he also said, this could potentially happen several times a day during a power outage, depending on solar array size, number of powerwalls etc. In my own system, right now, my powerwalls fill from empty to full by 11:30 am to noon.

If I was in a power outage situation, without the frequency change, and older UPSs that dont tolerate the high frequency, what would happen is, Power outage in the morning (lets say), solar + powerwalls continue on as normal and fill batterys and run the home until 11:30 to 12 Noon, powerwalls reach 100%, powerwalls shut off solar by raising frequency... UPS complain and beep (*and any other symptoms such as microwaves, LED lights etc).

UPSs beep / continue to provide power until they run out or until powerwall drops back down to somewhere between 90-95%... when that happens, solar kicks back on. Sun still shining, starts providing power to powerwalls and powers home, powerwalls back to 100%... repeat.

Right now, My solar generates close to twice what I am using, especially since I am not driving much. My solar runs until about 7pm. With my current home load, in an outage, the solar would likely blip on and off several times in the afternoon as my powerwall drained from 100, and kicked the solar back on when it hit 95% (as an example) and filled back up.

So yeah, it only happens in that instance, but depending on number of powerwalls you have, and size of solar, "that instance" could be really common in a power outage with the sun up.

Right, I understand all of that and it's a scenario that can happen.

But my main point is, and what I think some people may be misunderstanding, is that the consumer level UPSs will still be able to handle the micro-second switchover to PW power regardless of any frequency changes with the solar inverters, and they will continue to power the downstream devices until their batteries run out if they can't handle the increased frequency change.

Just because one might have PW2+Solar does NOT mean your existing UPSs will instantly fail and the downstream devices will shut off or power-cycle when there's a grid outage. I just want to make that point clear, that is all.

 

[BrettS]

Just because one might have PW2+Solar does NOT mean your existing UPSs will instantly fail and the downstream devices will shut off or power-cycle when there's a grid outage. I just want to make that point clear, that is all.

That is absolutely true. Any UPS will handle that cutover. However, if the power failure happens during the day and the powerwalls start at (or get to 100%) then there is a very real possibility that the UPS will be running on battery for so much time that it will run out of power and your downstream devices will shut off.

 

[gpez]

Replacing a UPS Battery With Super-Capacitors

Not an electrical engineer but know enough to be dangerous. I wonder if the discharge curve is sufficient for most residential UPS inverters. Seems like this would be the way to go if you were so inclined.