I'm going to have to read your post and ponder this a bit, thanks. Oh yeah did I mention that we lost grid power in the middle of the night, when there was no solar input, and at least in theory no need to adjust the AC frequency?
Bruce.
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Powerwall 2 + UPS Connundrum - and solution
- Thread starter NinjaVece
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- ups 65 hertz
I'm going to have to read your post and ponder this a bit, thanks. Oh yeah did I mention that we lost grid power in the middle of the night, when there was no solar input, and at least in theory no need to adjust the AC frequency?
Bruce.
wbhokie
Member
This is exactly what I did when I put in my powerwalls after the first power outage. (as I posted earlier in this thread) I switched the units that either did not perform well or required battery backup to Eaton UPS units with minimal backup capability (Including my desktop like yours) and now everything is on a complete solution. I've had several short switch-overs since then and the Eaton units work like a charm. They only need to work for seconds at most, so high end ones aren't necessary. I was able to sell my previous units on Facebook Marketplace to recoup the cost.
This is a long thread and I am just educating myself on this issue as a "soon to be" powerwall owner (2). Can you post the model number(s) of the eaton unit you purchased? Its likely in the thread somewhere, but I have not read the entire thread, but believe I understand what the issue is, and what that product is solving, so was hoping to find it without having to click through all the pages of this thread.
Any help from anyone with the eaton part that is confirmed working for home use (nas, router, etc) would be awesome.
wbhokie
Member
I use both of these units.
For something small like a router (low power) this is enough. (Eaton 3S550)
https://www.amazon.com/dp/B00906CH8...D20V&psc=0&ref_=lv_ov_lig_dp_it&tag=tmc064-20
For desktops, I use these (Eaton 5S700LCD), even though the above may still work for the short time necessary to switch over the power.
EATON 5S700LCD 700 VA 420 Watts 8 Outlets UPS - Newegg.com
I'm going to have to read your post and ponder this a bit, thanks. Oh yeah did I mention that we lost grid power in the middle of the night, when there was no solar input, and at least in theory no need to adjust the AC frequency?
Bruce.
That's why I said "maybe" on the solar input
If you look at the chart in that other thread you'll see that when the solar finally turns back on (~1700s mark) the frequency increases ever so slightly from just under 60hz to just over 60hz. Could be coincidence, could be related to the solar input or maybe the delta between the load and solar which is the net to/from the battery. Not sure why I didn't include the battery SoC in that pretty chart but it is in the data dump link in that thread (Powerwall 1.37.1 outage simulation - efe9a57b). You'll notice that my frequency never goes above 62hz even with 0 solar production and high battery SoC.
mspohr
Well-Known Member
Are you going to run your induction cooktop from this unit? Most induction cooktops require at least 1800 watts. I've run a single burner induction cooktop from a 12v driven 2000 watt "pure sine wave" inverter. Works well.
(Short rant: Drives me crazy that none of these UPS vendors tell you the energy capacity of their units. They all list output voltage/frequency and max power output but they don't tell you the battery capacity which is one of the most important cost and performance indicators.)
Since Tesla has but my Powerwall reservation from last year is on permanent ignore, I'm looking at alternative batteries and inverters. The Outback Skybox looks like a good solution (and puts out 60 Hz power so none of these UPS 66 Hz issues). Works with 48v batteries (any type). I have a lead on LiFePO4 batteries that would work well with the system. (Safer and more durable batteries)
http://www.outbackpower.com/products/true-hybrid-energy-system/skybox
UPS units usually express their battery capacity as a runtime at 50% load. From that you can infer the capacity.
If you go with an Outback solution, will you use it with grid tied solar inverters? To my thinking, any AC coupled battery system must have a way to curtail the solar when the batteries get full. This is the source of the 66Hz issue with the Powerwalls. I have never looked into how Outback handles this situation. Of course, Outback nomally recommends using solar charge controllers instead of AC coupling solar. That completely removes the frequency issue because the charge controllers automatically curtail the solar when the batteries get full. I really like the Outback solutions, but you have to pay more for the extra features that they provide to improve on Powerwall features.
Could you elaborate a bit as to why you think that the Skybox won't use high frequency to instruct your PV inverters to shut off during a grid outage? Specifically asking regarding your "puts out 60 Hz power so none of these UPS 66 Hz issues". Since it is UL 1741 SA listed I believe it will just the same as the Powerwall does. Check out "Declaration of Conformity" on page 4 here: http://www.outbackpower.com/downloads/documents/skybox/skybox_decl.pdf. Overfrequency maximums are listed at 66 Hz, which is what UL 1741 SA requires.
I know it's not perfect but most UPSs use standard AGM SLA batteries which are almost always 12v and have capacities from 6AH to 8AH. At 100% efficiency that's 72wh to 96wh per battery. Most small UPSs just have 1, medium sizes have 2, and larger ones 3 or more. You can look at what replacement batteries the manufacture recommends and do the math from there, but perhaps that's your point about them not listing the capacity up front!
mspohr
Well-Known Member
The Skybox has a separate circuit for charging the batteries and running the inverter. You can even configure the amount of power you take from the grid vs. solar. Also has the option for a generator input.
If the batteries are full and there is no grid, it can shut off AC solar input by isolating that source and keep providing 60 Hz to the house. However, it works best when you DC couple your solar to it. This gives it the most flexibility in handling solar input (and also saves buying separate solar inverters... just hook your solar panels directly to the Skybox). This is how I plan to install it. It can be configured to draw power from the batteries and the grid at the same time which is useful for TOU tariffs.
Highly configurable:
http://www.outbackpower.com/downloads/documents/skybox/skybox_prg_web.pdf
RE: UPS batteries. Yes, most of them are lead-acid and most of the time you can dig up the replacement battery number and find the size from that. It's just irritating that they don't specify it in their advertising. (Probably don't want to admit how weak their batteries are...). Of course, the problem with lead-acid batteries is that they die if you use their full capacity so should only discharge them to 50%.
JPP
Active Member
Just a shout out and thanks for the forums and this particular thread. When we folks here in NoCA had the last big PG&E Public Safety Power Shutoff, I was out for 5 days. I have a 9000W dual fuel (propane and gasoline) generator which I hooked up to my house (a mishmash of backfeeding and extension cords). The generator has a display with volts, frequency and run time (hours). For the 1st couple of days things seemed fine. I was able to power useful items and keep some electronics plugged into CyberPower and APC UPS going fine. On day 3 or 4, my various UPS started beeping and dropping off line. At first I could not figure out what the problem was. The generator was running and my lights and appliances were getting power. Then I remembered this thread on frequency issues. Sure enough, the generator (which is NOT an inverter model so relies on a very steady RPM to give steady frequency) was showing 62.5-63 Hz. Not much I could do about it, but at least I knew what the problem was.
And now that we in NoCA are in the 'new normal' of planned power outages for the foreseeable future, I have ordered up a couple of Powerwalls from Tesla to add on to a 16kW Solar City/Tesla system. Hope to get them installed by 12/21/19 to get the full tax credit and also avoid the reported issues with new 2020 CA building codes.
And now that we in NoCA are in the 'new normal' of planned power outages for the foreseeable future, I have ordered up a couple of Powerwalls from Tesla to add on to a 16kW Solar City/Tesla system. Hope to get them installed by 12/21/19 to get the full tax credit and also avoid the reported issues with new 2020 CA building codes.
Hey all, I registered to thank everyone on this thread for helpful info regarding this very issue that I doubt I could have found anywhere else. While I do not have a Tesla vehicle, I do have a pair of Powerwalls that were installed on the 1st of August this year to complement my 9.6kw solar array with a SolarEdge inverter. I, too, had noticed that my UPS units (also Cyberpower units) were not providing bridge power during the switch from utility to powerwall power during a service outage or controlled test. Thanks to this thread, I got rid of the UPS units I didn't need anymore and replaced my critical load UPSes with Eaton units. As one of my PCs uses a Seasonic power supply with PFC, I utilized one 5P1000 unit for that and cheaper 5S700 units for the rest. That has solved my issues and I can happily report that during controlled tests with fully charged Powerwalls, power cuts over with no interruption to any vital services.
I will throw out one more oddity just in case it helps anyone else who may come across the same situation. I have 2 ceiling fans that are controlled with remotes. As such, the lightswitch controlling mains power to these fans is always in the on position. The fans and fan lights are almost always turned off by remote. While on Powerwall supplied power, the LED lights in these fans will flicker with a very consistent and repeatable pattern which I have captured on video. If I turn off the power to these units by flipping the light switch to off, they remain off. Ironically, while very annoying to my dog, it makes a heck of a visual indicator for when we are on powerwall supplied power. That said, I would not appreciate it if we had any epilepsy sufferers about.
I will throw out one more oddity just in case it helps anyone else who may come across the same situation. I have 2 ceiling fans that are controlled with remotes. As such, the lightswitch controlling mains power to these fans is always in the on position. The fans and fan lights are almost always turned off by remote. While on Powerwall supplied power, the LED lights in these fans will flicker with a very consistent and repeatable pattern which I have captured on video. If I turn off the power to these units by flipping the light switch to off, they remain off. Ironically, while very annoying to my dog, it makes a heck of a visual indicator for when we are on powerwall supplied power. That said, I would not appreciate it if we had any epilepsy sufferers about.
Hi @aclosedmind and welcome!
I'll copy a response I used earlier to hopefully explain what is going on today. There is a lot of misinformation and I actually get a little sad when people replace perfectly good UPSes with "new" ones that are more tolerant of frequency variations. Using Eatons addresses the symptom but not the underlying frequency problem, which you're experiencing with other electrical items in your house. You may also notice other devices behaving oddly: motorized equipment (microwave, garage door opener, etc), inductive cooktops, AC clocks, as well as LED lights. What you'll want to do is actually get Tesla to fix your off-grid frequency maximum. Details on that below.
Here is what's happening:
When paired with solar and with no grid connection the Powerwall signals to the inverters that it is full by increasing the AC frequency from the standard of 60hz in the US. Modern inverters will shut down starting as low as 60.5hz after a few minutes and instantly at 62hz. This behavior can be confirmed if your inverters are UL 1741 SA certified, the designation that the inverter was tested and properly shuts down in the time allotted at these frequencies. Tesla, however, has pre-configured Powerwalls to set the frequency to 66hz in this scenario which is clearly too high as at these high frequencies sensitive electronics can misbehave. The best guess here is that Tesla didn't want to risk a non 1741 certified inverter staying up when the batteries are full so the default is something much higher.
If you have a UL 1741 SA certified inverter (almost assuredly your SolarEdge is) the fix is simply to call Tesla to tell them you have a 1741 certified inverter and have them remotely update your Powerwall configuration to a maximum 62.5hz. This took me all of 3 minutes to do on the phone with them.
Of course this ONLY when the grid is unavailable to dump excess solar power to, any other time the Powerwall will hum right along at 60hz and your LED lights will be happy. Once your maximum frequency is fixed you could use your old CyberPower UPSes again as well during a grid outage and high PV output.
More details here: My grid outage frequency issue is resolved!
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One additional note: Newer inverters have the capability to ramp down production if configured to do so. SolarEdge inverters all it "P(F) Power Frequency" (https://www.solaredge.com/sites/default/files/application_note_power_control_configuration.pdf, page 6) and my Enphase IQ6 microinverters call it "curtailment" or "ramp down" (https://enphase.com/sites/default/f...Considerations-AC-Coupling-Micros-Battery.pdf, page 6).
This is extremely helpful to help prevent the "see-saw" effect of your solar inverter turning on and off during a grid outage as the Powerwall batteries charge and discharge. The trick would be to configure your SolarEdge to start to curtail production starting at 60.5hz down to 0 at 62.5hz. Done properly your solar production will increase dynamically with your house consumption and Powerwall charge level. This will help keep your Powerwall charged close to 98-99% during a grid outage rather than drop down to 92-95% until the frequency goes back below 60.5hz and your inverter turns back on.
This is extremely helpful to help prevent the "see-saw" effect of your solar inverter turning on and off during a grid outage as the Powerwall batteries charge and discharge. The trick would be to configure your SolarEdge to start to curtail production starting at 60.5hz down to 0 at 62.5hz. Done properly your solar production will increase dynamically with your house consumption and Powerwall charge level. This will help keep your Powerwall charged close to 98-99% during a grid outage rather than drop down to 92-95% until the frequency goes back below 60.5hz and your inverter turns back on.
I did read that and will be doing that for sure. I'll also pass this along to my solar installer as frankly this is something they should have done (provided that this change was available when it was installed August 1). As for my Cyberpower UPSes, they were getting a bit long in the tooth and frankly weren't needed everywhere I had them. I had accumulated almost a dozen over the past 5 years or so and this was a good time to give them to friends who are fine replacing batteries or using them as is until thats needed. Going with fresh Eaton units gets me fresh batteries and a guaranteed working condition without too much of a significant cost, but you are right and the most fiscally responsible thing would be to have kept the UPSes I already had. I'm down to 3 total now and that should be all I need.
Such great information here, I have linked it to my installer for their review as well.
This is kinda along the lines of what I did...but it took a couple of service calls (which accomplished basically nothing since I had already provided them all the information they needed) and me finally saying "look can you just please just configure my system so it doesn't let the AC frequency go above 62.5 Hz" for them to do it. So in the end I got the result I needed, but this was perhaps not the most effective way. It sounds like what @gpez did was less hassle...maybe using the magic word "UL 1741 certified inverter" might make it go faster?
Good luck!
Bruce.
Yeah, I've found 1st tier support is hit-or-miss. I called once last March concerning my Powerwalls and one agent told me that the "whole point of a grid-tied solar system is that it shuts down automatically when the grid goes down". I had to inform her that one of the main selling points of the Powerwall is that it can keep solar running if there is a grid outage. It sounded like she no idea what the Powerwall was or how it functioned.
I thought our Powerwalls had been adjusted but after our recent 8 day off-grid test, the next morning the power went out for a minute and I realized the frequency was still an issue when the Powerwalls are fully charged. I will be sure to mention "UL 1741 certified inverter" when I call in next time.
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