Solving the Tesla Powerwall frequency problem

TLDR: Useful if Tesla Powerwall frequency shifting during outages is affecting appliances like clocks, furnaces, uninterruptible power sources (UPS), etc. Want to skip right to fixing the Tesla Powerwall frequency problem? Click here.

In February 2018, we installed a Tesla Powerwall 2.0 on our Vermont home. We get around thirty outages a year, and for the last 4 years this device has provided us with a reliable automatic backup electricity source capable of running our home through outages of up to two days. (Read more about my experience with our Tesla Powerwall here.)

Whenever there was a lengthy outage, I noticed that my old-fashioned digital clocks would run a little fast. I’d reset them to the correct time and didn’t think much about it.

Until one day…

Houston, we have a problem

Earlier this year, I reluctantly dismantled our 38-year-old solar hot water and space heating system, and replaced it with a gas boiler. (One of the system’s large, expensive solar storage tanks had sprung a leak, and I would have had to replace all three tanks. Our solar collectors were still working flawlessly, but I worried that they might not last much longer.)

The gas boiler, a high efficiency Alpine condensing boiler, was installed to heat a new stainless steel domestic hot water tank and the two existing radiant floor heating systems. After dealing with the inevitable teething troubles, the system was working well.

Until we had a power outage while the boiler was running.

Passing the small utility room that contains the heating system, I noticed a red glow that was definitely not normal. Going in, I saw that the boiler’s touch screen display had turned red. The boiler had shut down with a “hard lockout”. Looking up the displayed error message “Fault 23” told me that the boiler was unhappy with the Tesla Powerwall’s power.

This was not OK. First, the boiler would not operate during a power outage. Furthermore, it would not turn on automatically once utility power returned. That’s because you have to manually reset the hard lockout using the boiler’s touch screen.

So if we left our home for a few days and a power outage occurred during that time, the boiler would not operate until someone entered our home and reset it. Having our plumbing freeze and plants die while we were away was not acceptable.

Diagnosing the problem

It wasn’t hard to figure out what was happening, once I remembered the previously ignored clue that some of our clocks ran fast when using Powerwall power. These clocks are the old-fashioned kind that keep time based on the national electric utility frequency of 60 hertz (Hz). Clearly, the Powerwall must be providing backup power at a higher frequency.

To my surprise, a quick Google search told me that Powerwalls supply power at 66 Hz when they are at full or close to full charge! My furnace was shutting down because, unlike the rest of my appliances, it would not operate correctly at 66 Hz. But why would Powerwalls do this?

Well, it turns out that many Powerwalls are used as storage for photovoltaic (PV) solar panels. PV systems also use an inverter, like the one in a Powerwall, to generate household power. And when the house’s electrical needs are being met with the Powerwall charged to or near full, there’s nowhere for additional solar-generated electricity to go. So the Powerwall is designed to switch to 66 Hz under these conditions. PV inverters, like my furnace, see the frequency out of the normal spec and shut down. The Powerwall supplies the home until it has spare capacity to be recharged by the solar panels, and then drops its frequency down to 60 Hz. Until then, the solar inverter (and my furnace) will shut down.

Ok, so I understand the problem and the reason Powerwalls are designed this way. But I don’t have PV panels, and I want my furnace to work when there’s a power outage! What could I do?

Fixing the Tesla Powerwall frequency problem – option 1

Luckily, as you might expect, I wasn’t the first customer to have this problem. More Googling indicated that I could call Tesla and ask them to remotely update my Powerwall to reduce the frequency of power it provided under high charge conditions.

So I did. After a long hold time for Tesla Powerwall Support [(888) 765-2489], I spoke with a friendly technician, Manny. He confirmed that Tesla will make this change and placed an order for my system. Manny told me the change usually took 3 – 5 business days, and he would get back to me when they did it.

I waited. After nine days, I called back to get an update, and Andrea told me the queue was currently running 10 – 15 business days. So I waited some more.

Sixteen days after I’d spoken with Manny, he emailed me that Tesla had made the change. Great! Now, I wanted to test to see if the fix worked.

Testing that Tesla’s update worked

I didn’t want to wait until a power outage occurred while my furnace was running. So I decided to manually switch our home to Powerwall power.

I hadn’t done this before, so I investigated my Powerwall installation. It’s mounted on an external wall, so it’s easy to see the components. Please note that there are several ways to install Powerwalls — don’t assume that your configuration will be the same as mine. Here’s a photo, with the components labeled, of my setup.

Tesla Powerwall frequency Grid power flows through my utility meter through the gateway to the Powerwall disconnect, which is hooked up to both the Powerwall and my main home breaker panel.

For my setup, to switch our home to Powerwall power manually you simply have to open the gateway box and turn off the grid disconnect switch.

Tesla Powerwall frequency

After flipping the grid disconnect switch, I went inside and turned up a thermostat so our boiler would fire up. Success! The Alpine now worked happily on Powerwall backup power!

I don’t own a multimeter that includes frequency measurement, but I found another way to discover the frequency that my Powerwall now generates. By logging in via your gateway’s Wi-Fi network, it’s possible to view the operating frequency of your Powerwall. These instructions provide a guide. I discovered that my Powerwall’s output is now between 62.1 – 62.3 Hz. Apparently, that’s close enough to 60 Hz to keep the boiler running.

Fixing the Tesla Powerwall frequency problem – option 2

Although I solved my boiler problem, that doesn’t mean other appliances or devices are immune from Tesla’s frequency switching technology. If that turns out to be the case for you, there is another option that should work, though you’d have to pay for it.

The trick is to use an online aka double-conversion uninterruptible power supply (UPS) to power the troublesome device. (Offline/Standby, Line-Interactive, and Automatic Voltage Regulation types of UPS don’t change the frequency of the power supplied.) An online UPS charges a battery that runs an inverter providing 120 volts, 60 Hz power independent of incoming power quality. When grid power fails, this type of UPS has no transfer time. Plug the problematic device into an online UPS that has enough volt-amp (VA) capacity and you’re all set. Note that the backup time such units provide is irrelevant since they will still be receiving power from the Powerwall.

The only drawback to this solution is the expense. An online UPS costs more than the other types. The least expensive unit I could find via a quick search, the Maruson 1000VA Online Double-Conversion UPS, costs almost $500.

Conclusions

Once again, I’m very happy with my Tesla Powerwall. It would be nice if an installer or owner could make this frequency change, rather than waiting for two weeks for Tesla to do it. But at least there was a fix that only cost some time for research and a couple of phone calls, and my boiler power problem is resolved.

I hope this article will help anyone else who runs into the same problem. Please share your experiences and suggestions in the comments below.

 

Fixing a Tesla Powerwall that isn’t charging

fixing a Tesla Powerwall In February 2018, I took advantage of an excellent Green Mountain Power (GMP) program to install a Tesla Powerwall 2.0 on my Vermont home. For just $1,500, GMP installed a 13.5 kWh Powerwall on the outside of my home, providing us with an automatic back up electricity source that has proven capable of running our home through continuous outages of up to two days. (Yes, we get those kinds of outages now and then in rural Vermont.) Fixing a Tesla Powerwall is definitely GMP’s responsibility — but recently I was able to solve a charging problem myself.

Why GMP subsidizes Powerwall installation

Given that an installed Powerwall costs about $10,000, you might be wondering why GMP installed mine for only $1,500. The answer is that they have the right to suck power out of it when there’s a system wide power consumption peak. With several thousand Powerwalls like mine currently installed around Vermont, these combined units can supplement conventional power sources with tens of megawatts of power, reducing GMP’s need to buy expensive peak power.

I get automatic reliable power when the line power to my house is interrupted. GMP gets lower power purchase costs. Win-Win!

How the Powerwall has worked so far

My Powerwall has worked perfectly for eighteen months. In that time it’s taken us through 43 outages. Most of them are short and last less than an hour, and we don’t even realize the power was off until later. Our longest (54 hours) began on November 27th, 2018 and that’s the only time our Powerwall got completely discharged. In total, the unit has supplied 66 hours of backup electricity since we purchased it.

I know all these stats because Tesla provides an app that monitors your Powerwall, showing your backup history…

fixing a Tesla Powerwall …current power flows…

Powerwall power flow

…and historical power flows.Powerwall historic power flows

The 42nd power outage

On August 9, 2020, we had a 3 hour outage. It turned out that a tree fell on the power line that snakes up the ten miles of road between our home in Marlboro and the feeder point in Brattleboro. The Powerwall worked perfectly, but when utility power was restored, the Tesla app showed that though Powerwall was still 80% charged, there was no power flowing between the electricity grid, Powerwall, and our home.

This had never happened before.

The green light on Powerwall was steady, so it was “enabled” and communicating with the Gateway.

First I tried turning off the Powerwall, using the switch on the side. The house power remained on, and the big green LED on the side slowly dimmed. I waited for ten minutes until the light was out and then turned the unit on. No improvement. Strike 1.

Second, I gingerly opened the Gateway box, something I’d never looked at before (or been told anything about by the installers.) There was a reset hole, but a flashlight showed me there was no button to reset. The Gateway box has a single breaker which I turned off. The app then came to life and showed that the Powerwall was powering the house, draining the battery. Encouraged, I turned the Gateway breaker back on. The house became powered by the grid again, but, the app display went back to showing no flows. Strike 2.

Fixing a Tesla Powerwall charging problem

Well, when all else fails, read the manual! I’d never received a Powerwall owner’s manual, but found it online and discovered these instructions in the Troubleshooting section:

If the Gateway and Powerwall are both unresponsive:
1. Turn off Powerwall by setting its switch to the OFF position.
2. Turn off the AC breakers for the system (Gateway and Powerwall).
3. Wait for at least one minute.
4. Turn the AC breakers back on.
5. Turn on Powerwall.

I was reluctant to do this, since I knew it would turn off the house power completely and I’d have to run around and reset all the clocks. (A classic First World problem.) Anyway, sometimes manuals prove useful, because after I followed these instructions — hallelujah! my app showed flows, including the welcome sight that my Powerwall was being recharged by the utility company. Everything worked again!

I hope my experience fixing a Tesla Powerwall that isn’t charging is helpful to anyone else who experiences this problem.

Any other Powerwall tips and experiences to share? Add a comment below!