Power Quality - significant dip during EV charging, causes?

This all started with some lights flickering at 4AM with our new EV charging a couple weeks ago, and each morning our router would be offline and the time on one of the coffee makers would be wrong by 20-30 minutes. We couldn’t get the issue to reproduce during the day. Bought sense to try and get to the bottom of this, and on day 2 with the sense installed I have my first recording of the event!

So you can see when the EV starts charging there is a drop, but within tolerance, then there is a really significant drop to 80V. This was enough to cause the EV to stop charging and flag an alert (photo of alert attached, you can see the time stamp matches the Sense flag time for voltage drop).

So I think a call to the utility is in order. I have checked my panel and the grounding rods and connections, so I am pretty confident the issue is somewhere upstream of the meter. Has anyone in the community seen this before? Are there any best practices to get the utility to root cause this correctly?


All 2 phases drop at the same time, so it does not seem like a floating ground/neutral of any kind.

Can you use your power meter , zoom in around the time of charging and post a screenshot of that ?

this is how an EV charged a couple of days ago (during the day so it also shows solar)

As you can see this EV tapers down at the end of the charge session while charging to full ( I charge mine only to 90% and it ends abruptly)

It seems your clipper creek starts to charge for about 90 minutes and when it stops charging a DIP occurs instead of a peak.

What kind of EV do you have?
How many amps are you charging your EV?
Do you have solar?
Do you have battery storage?

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That graph shows two or three voltage drops below 115 Volts. And the time scale would seem to show that they occurred after 6 a.m. Or am I reading that wrong?

If the charger did shut off at 5:23 (and did not restart), It’s possible this is unrelated to your EV.

You are reading the graph wrong - the list of recent dips and spikes clearly shows the first one happened at 5:23AM, the exact moment the charger detected the issue.

ps: I see a voltage drop on my mains:

When my EVs are charging, but do not see the dramatic deep dips the OP logged.

I’m seeing the charging stop just after 6. So is this one hour “shift” something to do with daylight savings? And what about the second drop an hour later when the charger doest seem to be on?

I believe you guys, just not sure what I’m not seeing that you are.

This is the plot from the power meter showing the charge, it ends when it drops out at 5:23. The car is a Tesla M3 using a Gen 3 wall connector drawing 48A on a 60A breaker.

More data also updated in the power quality graph, so I now have 3 dips recorded. I put an arrow at the times the car was charging. It could be it is not related to the car, we just started noticing it because of the car?


I’m seeing this:

But I take back what I said - you’re reading the graph correctly, but I trust the time to be more likely on the log entry above, when they are different.

Either way, i think you’re right to give your local utility a call.

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You could pre-empt discussions with the Utility by augmenting your Sense Power Quality data and EV logs with an understanding of your distribution transformer.

If you’re in a typical pole-mounted situation you may be able to figure out how big (kVA) it is and how many people it serves. Looks to me like you may be in upgrade-required situation so maybe doing some research could speed the process.

I am not sure what to make from all this.
To me it looks like your EV starts to charge around 5:20am.
The fact that there is a 5 Volt drop * 48 amps = 240 watt that is “lost” because of the energy draw and imo that is withing normal limits. Kevin1 sees a 2-3 volt drop so that is better than yours so room for improvement.

The dip Sense detected at 5:23 was while your EV was already charging.
I don’t understand why your M3 would start charging “slowly” and 7 minutes later would ramp up to 48 amps.
Unless another device started using electricity just before your M3 started charging and it is merged in the graph. But I don’t see it drop down later in the graph so I assume all power usage is from charging your M3.

While in the “low charging mode” sense detected the low dip of 80 volts ?!
No logic in that imo.
I had flickering lights and they put a fluke recording device on my inputs for a week and then acknowledged I had a problem and came and upgraded the 25KVA transformer at the street for a 75KVA and upgraded the overhead wires in the street and to my weather head.
Wouldn’t hurt to ask if your utility could do similar monitoring at your location.

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Is that after the squirrel?

This seems like an opportune moment to suggest something I’ve pondered as “last resort” when confronted with a difficult Utility (if that was/is the case) …

  • Inspect transformer and trace who shares it with you.
  • Assume they don’t have Sense (?)
  • Send them a Sense as a surprise and ask them to collaborate with you.

If you or neighbors have solar or EVs or both it could ultimately be a way of giving metrics to the Utility that weigh in your favor(s) in some fashion.


The squirrel was way before, that was may 2021 :wink:

Replacing the burned out unit, you can see the scarred wood on the pole

Burned unit on the ground.

It stored the acorns everywhere

It certainly had stashed a lot of acorns up and around the unit.

I had notified my utility that I intend to charge my F150 lightning with 80 amps.
80 Amps x 240 Volt = 19200 Watt.
My home together with 4 others on a 25KVA transformer didn’t sound fair.
Gave them schreenshot of the LAB notification of dips while charging with 32 amps with my current EV and told them about flickering lights in the house.
After that they installed the inspection unit for a week.
After that they pulled permit etc and 6-8 weeks later they replaced both transformer & cabling

Original transformer hanging from the bucket and the new one on the right.

I think they took me seriously because I could show them the surges/dips from Sense before hand.


The squirrel thing is hilarious. I also like the idea of sharing sense with the neighbors, but might I offer common.sense.com as the address??

I have an update to share also. The utility came out today. I showed them the data log in the app, they were super impressed. I think this guy might be buying a sense for his home. What we found was the transformer has signs of leaking fluid. I tried to get a picture where you can kind of see it:

Needless to say, I am really excited. I should have a new transformer in the next couple of hours. Hoping that is going to be the fix. I will report back either way once that is in place and let everyone know how it turned out.

Thank you all for the help and analysis to figure this out, it made the conversation with the utility super easy and right to the point.



The Labs are really now key to the Sense experience and I think demonstrate in a compelling way how well crafted and narrowly focused analytics and graphics can really drive home the idea that Sense has a lot to offer besides device disaggregation.

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Some quick follow up with the new transformer. I took the plot and tried to manually align it with my power meter plot and where before we saw voltage moving during the time of car charging load, we don’t see that anymore. So this seems to be a confirmed solution. I will continue to monitor over the next few days of course, but I think this shows we got it. Thanks again for all the great hints and feedback from the community to help me figure this out!