Odd behavior with my Powerwall+

[furuike]

Hi, I've had a Powerwall Plus installed with 8.6kW peak of solar since November. I've noticed a problem from time to time, I've contacted both the installer and Tesla and so far it's not resolved, it still happens.

The problem is that, from time to time, my battery temporarily stops charging or discharging. Frequently this means my battery is well above my reserve limit, yet it will not discharge and I instead pull energy from the grid. Occasionally, this means that I end up overproducing solar and selling energy back to the grid instead of charging the battery.

I've logged into to TeslaOne to see if there are any faults, in general I do not have any. Well I take that back, Tesla did tell me one time I do have high voltage from the utility. I can corrobate this, sometimes I see 252-254VAC on the line, which is almost 5% above 240VAC.

This happens perhaps once or twice a week, it's hard to definitively give a cause, but sometimes it happens when a hard load kicks on like my AC. In fact, that is the state now. At 6PM, my AC unit kicked on, and right around that time, my Powerwall stopped providing power. Right now it's sitting at 100% and not discharging, instead the grid is providing power. (See attached graph).

When I first called Tesla, a tier one person looked at the logs and said my coolant was low, and recommended I contact my installer to refill it. (Bear in mind this unit was just installed 6 months ago). I found this hard to believe, I asked why it would be low if it was just installed and I see no evidence of leaking. She said they deliberately do not fill them full at manufacture. I found this even less plausible, especially since my installer had never filled any coolant during installs.

Anyway, my installer did come out and look at a few things, they found some loose neutrals in my panel, and also noticed the highish voltage that Tesla did. But the problem never really went away.

Occasionally resetting the system gets it working again, but sometimes not. Usually I just have to wait. It may take 30 minutes or 8 hours before the battery starts discharging again.

Has anyone else had a problem like this?

 

[BGbreeder]

Can you post a picture of the specification plate on your Powerwall +? Do you know how your Powerwall is programmed, e.g. which grid/voltage settings it has? What utility provides your power? Is your house on its own transformer?

What is the grid voltage in non-solar hours, e.g. 21:00-22:00 and 4-6:00am?

We have been having voltages in that range, and our Powerwall 2 are not going into standby. However, we are not trying to start an AC during times when the Powerwalls are providing power.

My first guess would be that your voltage does go higher than 254, and the higher voltage puts the Powerwall into a standby state. My second guess is that as the Powerwall tries to accommodate the startup load of the AC, the overshoot when the inrush current drops puts the voltage at the Powerwall out of range (just a guess). My Powerwall 2 have a listed maximum voltage of 252 or 253VAC.(Yes, both are called out depending on the grid settings for the Powerwall.)

I would suggest that you check with your utility and see if they will lower your voltage preemptively, (either with turning down a voltage regulator on the circuit, or by removing a capacitor bank) and/or install a data logger.

Tesla support should be able to read your logs and see whether over voltage alarms are there, but I do not know the level of detail, nor the granularity of their data logging.

All the best,

BG

 

[furuike]

Can you post a picture of the specification plate on your Powerwall +? Do you know how your Powerwall is programmed, e.g. which grid/voltage settings it has? What utility provides your power? Is your house on its own transformer?

What is the grid voltage in non-solar hours, e.g. 21:00-22:00 and 4-6:00am?

We have been having voltages in that range, and our Powerwall 2 are not going into standby. However, we are not trying to start an AC during times when the Powerwalls are providing power.

My first guess would be that your voltage does go higher than 254, and the higher voltage puts the Powerwall into a standby state. My second guess is that as the Powerwall tries to accommodate the startup load of the AC, the overshoot when the inrush current drops puts the voltage at the Powerwall out of range (just a guess). My Powerwall 2 have a listed maximum voltage of 252 or 253VAC.(Yes, both are called out depending on the grid settings for the Powerwall.)

I would suggest that you check with your utility and see if they will lower your voltage preemptively, (either with turning down a voltage regulator on the circuit, or by removing a capacitor bank) and/or install a data logger.

Tesla support should be able to read your logs and see whether over voltage alarms are there, but I do not know the level of detail, nor the granularity of their data logging.

All the best,

BG

Thanks for the reply!

My Powerwall lists the following for AC input/output:

Nominal Voltage -- 100 / 120 / 200 / 208 / 220 / 230 / 240
Voltage Range & Maximum Continuous Current :
90-110 VAC 25A
114-126 VAC 24A
180-220 VAC 25A
198-220 VAC 24A
198-242 VAC 25A
207-253 VAC 25A
228-252 VAC 24A

I logged in to my TEG. The Gateway is set to 60Hz_240V_s_IEEE1547a_2014
UVR = 211.2V (2 sec)
OVR = 264V (1 sec)
UFR = 59.5Hz (2 sec)
OFR = 60.5Hz (2 sec)

Inverter reconnect time is 300 sec.

I'm pretty sure the stuff I read from the Gateway are limits and tolerances for islanding, I don't think it relates to the battery, correct?

 

[furuike]

Also I live in Ohio, my utility is The Illuminating Company. I used to be on a transformer I shared with my neighbor. The transformers are still on the pole, but because we had so many transformers blowing up the power company rewired my street some years ago to be directly off a 240V line on the power poles, and the transformer is at the corner of my street. I'd imagine I share grid power with 10-20 other houses.

 

[furuike]

Also my Powerwall plus separately lists the inverter ratings:

Nominal grid voltage (input / output): 208VAC / 240VAC
Grid voltage Range: 183-228.8VAC / 211.2 - 264VAC
Maximum Continuous Output Power On-Grid 6.6kVa / 7.6kVa

... etc

 

[BGbreeder]

@furuike Congratulations on being a customer of one of the older utilities in the US!

Having 10-20 homes of a larger neighborhood transformer seems a little unusual, and may explain why the voltage is up. Have you checked your voltage after dark evening and morning and compared that to peak solar voltages?

It is hard to believe that a line shared with 10-20 homes could spike to more than 264 for more than a second, but strange things do happen. I'd ask the Illuminating Company to come out and put a monitor on your meter.

All the best,

BG

 

[furuike]

Hey just an update.

We have a heat wave this week in Ohio and today the utility warned there may not be enough electricity supply to meet demand. My battery went kind of offline last night because the voltage was high, perhaps 253-254V. Then this morning things seemed to be working again, and solar was producing. I noticed that my solar production stopped around 1PM. When I got home from work, I used TeslaOne to connect to my gateway. It was reporting 256-258VAC on the grid. First I tried doing a system/stop restart, but this didn't change the behavior. I called Tesla Powerwall support and explained the situation, and that I suspected high voltage.

They agreed this was likely the case, and they suggested a simple test: open my main service breaker in the gateway, and take my house off grid. I did this, and the battery took over immediately. Then after perhaps 5 minutes, the inverter started generating solar again. Then Tesla suggested I reconnect the grid breaker. If the system stays offline, then I know it's because the grid voltage is out of spec. If it doesn't, then there is some other problem.

I did this and can confirm my system stays off grid because grid voltage is out of spec. TeslaOne reports the grid at 258V, while my house runs at a clean 240VAC right on the nose. Also the TeslaOne app does tell me the system has a grid overvoltage alert, but this doesn't show anywhere in the app. I talked more with the Tesla technician and we agreed that the app should have given me an alert saying that grid voltage was too high, and it should have islanded for me. She referred to a recent situation in South Australia where power between two large cities was disrupted, causing overvoltage for some, but that many customers' solar did not island and they should have.

So it seems like there is a bug wherein the system will not go into island mode when grid voltage is out of spec high. (I believe max allowed voltage is 240VAC + 5% = 252VAC.)

Anyway, I guess I'm in off grid mode for a while. Tomorrow I plan to call the utility and complain. Good thing it's around the summer solstice as there is lots of solar.

 

[furuike]

I looked into this more and realized I wrote above that my system is designed to trip overvoltage at 264V. So 258 or 259V is not enough to cause the contactor to open, but it is beyond the rating of the Powerwall battery of 253V.

I have been monitoring voltage and of course when the battery is generating AC to power my house, it has to generate voltage 1-2V above the grid voltage so as to power my house, which makes it even harder I suppose.

The odd thing is that my inverter is rated to 264VAC, so I don't have a good reason for why it tripped unless voltage exceeded 264VAC (it may have, I wasn't home at the time). But if it did exceed this for more than a second my contactor should have opened, so it doesn't make sense.

Anyway, I called my utility and they said they deliberately put high voltage on the lines so that with all the AC running during the heat wave, they still meet voltage specs in most places. He also described a complicated systems of capacitor banks automatically switched in at substations that could cause temporary overvoltage if the voltage monitors or programs that control them experience problems. He passed my message onto other teams but said there is no reason to visit as there is nothing for them to do.

He said most customers have no idea what voltage feeds their house, but a fraction of a percent do notice as it causes equipment problems, and they get lots of phone calls from them. I guess now I'm one of those customers.

 

[yblaser]

I had an issue a couple of years ago with the grid voltage going too low during a heat wave. I think it got down to about 205-215 V and the solar and PW went into standby. I went into off-grid mode for an hour until the voltage recovered. I believe what exact voltage the PW and solar go offline will depend on the grid profile loaded for each product and not the absolute limits in their individual specifications.

 

[BGbreeder]

I looked into this more and realized I wrote above that my system is designed to trip overvoltage at 264V. So 258 or 259V is not enough to cause the contactor to open, but it is beyond the rating of the Powerwall battery of 253V.

I have been monitoring voltage and of course when the battery is generating AC to power my house, it has to generate voltage 1-2V above the grid voltage so as to power my house, which makes it even harder I suppose.

The odd thing is that my inverter is rated to 264VAC, so I don't have a good reason for why it tripped unless voltage exceeded 264VAC (it may have, I wasn't home at the time). But if it did exceed this for more than a second my contactor should have opened, so it doesn't make sense.

Anyway, I called my utility and they said they deliberately put high voltage on the lines so that with all the AC running during the heat wave, they still meet voltage specs in most places. He also described a complicated systems of capacitor banks automatically switched in at substations that could cause temporary overvoltage if the voltage monitors or programs that control them experience problems. He passed my message onto other teams but said there is no reason to visit as there is nothing for them to do.

He said most customers have no idea what voltage feeds their house, but a fraction of a percent do notice as it causes equipment problems, and they get lots of phone calls from them. I guess now I'm one of those customers.

As @yblaser points out your system responds to voltage variations will depend upon how the Gateway is programmed.

The Gateway on our system logs errors when the voltage exceeds 252. You may want to check your utility tariff and regulatory documents to see what the utility commits to for voltage, but generally it is 240V +5%. I believe Ohio law specifies ANSI for its distribution service voltages. Chapter 4901:1-10 - Ohio Administrative Code | Ohio Laws, which is 252VAC maximum.

Voltage Tolerance Standard – ANSI C84.1 – Voltage Disturbance

Putting higher voltage on to a a distribution circuit when the load isn't there sounds like a pixie dust explanation to me. If the voltage is intentionally high and you suffer equipment damage, they will own the resulting damage. A utility might alter their capacitor banks as the voltage droops, but doing so in advance does not sound well run.

There's a thread on power quality; Power quality issue: possible causes?

All the best,

BG