Electrical Interference When Charging?

Discussion in 'Clarity' started by M.M., May 16, 2018.

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  1. M.M.

    M.M. Active Member

    This is not a question I actually expect to get any responses to, but I figure it doesn't hurt to ask since I expect it to take a while to pin down and another data point would be nice.

    Symptom: While charging at 240V/30A, the AC/DC converter in the car makes what sounds like a rattling noise. It is pretty clearly audible near the rear wheel well, and is not the same sound or source as the cooling pump, fans, or fluid flow noises that the battery thermal system makes.

    Anybody heard this? It would not be normal behavior, and you would probably know if it was the same thing, because...

    ...anything with a susceptible power supply in the entire house makes the same rattling noise. LED lightbulbs, UPSes, and breakers, even those separated by a subpanel, several breakers, and over 100' of wiring from each other. It must be some kind of harmonics being injected (I haven't yet managed to get a scope on it while it's doing it to see if it's visible in the waveform), but I don't yet know of what sort or from what.

    It's a pain to diagnose because it has only happened twice in as many months, I changed three things at once (new car, new level 2 charger, new subpanel) so I can't pin down the source, and the actual issue is so strange that several seasoned professionals I've asked are completely stumped.

    One of the possible sources in the car itself (but it could also just be another power supply suffering from whatever weird harmonics is causing the rattling noise) so I figured I might as well ask just in case somebody else has had something similar. I can say that since the car charging at 30A is definitively the only thing that causes it it's either the car, the charger, or the breaker.

    Anyway, just throwing that out there.
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  3. K8QM

    K8QM Active Member

    I wonder if its some sort of arcing that then gets transposed on the line. Is it possible that the reason it's only happened intermittently is because some other large load needs to be running at the same time such that with enough of a current draw some component of your system has an issue?

    Could it be a main breaker, slightly loose/tarnished connections in the box, etc that become "unhappy" when the car is drawing 30A along with a hot water heater, oven, clothes dryer, etc? You may be able to test that by firing up several appliances while charging.

    I had a similar issue on a smaller scale that turned out to be a breaker that was was badly tarnished from being slightly loose so as the load increased it would cause flickering lights but with a small load it was fine.

    That's my 2 cents but it may only be worth a penny.

    Last edited: May 16, 2018
  4. Rich Shaffer

    Rich Shaffer New Member

    Posted this back in March. Still get that intermittent buzzing (near drivers side rear wheel) but only when charging at high rate. If I dial the amperage back, the buzzing stops. New 8/3 copper line and new 40A breaker in 200 amp panel. Don't think there is an issue with supply. Have noticed the voltage can drop as low as 236 when charging at high rate.

    Hello, Other than the issue I had at a chargepoint public station,(have not returned to it) have had no charging issues as of now. Have a Juicebox 40 (Set to a max of 32 amps) on dedicated 40 amp line in the garage. Yesterday used almost all of my battery range. Plugged in and heard loud buzzing from the rear of the car. Car was drawing 30 amps 239 volts at that time. Almost seemed like it was drawing too much current. I dialed the amperage back to 24 and the buzzing stopped. Resumed 30 amps and the buzzing returned. Anyone else have a similar issue?
  5. rodeknyt

    rodeknyt Active Member

    I hear a rattling type of noise each time I open the charge door with the fob. Never really concerned me, just figured it is something happening to get the charger awake and ready. I use the timer and charge it during the wee hours, so I've not been near the car to hear if it makes any sound during charging.
  6. Sandroad

    Sandroad Well-Known Member

    How did you dial in a specific charging amperage?
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  8. M.M.

    M.M. Active Member

    This is a feature of the Juicebox.

    This is completely unrelated to what I'm talking about, and is almost certainly as you say just something to do with enabling the charger. I'm describing a rattling-like electrical noise that is constant for as long as the car is charging at 30A, and can be heard in the breaker panel and most switching power supplies anywhere else in the house.
  9. K8QM

    K8QM Active Member

    Kind of interesting charging tonight. I had used a public charger while hiking at a local nature reserve so I didn't need much charge when I got home. Our home charger is in a detached garage so I wasn't near the car when it was charging but I noticed that our kitchen LEDs were flickering a bit which is not a normal occurrence.

    When I pulled up the chart of charging in KW versus Hours above I saw that unlike the normal fairly clean graph like on the left of the chart from last night tonights was pretty spikey for the first 10 or 15 minutes.

    Is it possible that the interference issue is occurring when charging is started on a nearly full battery? That certainly isn't an explanation but could be another data point in finding the cause.

  10. AlanSqB

    AlanSqB Active Member

    The car seems to generate line noise when charging at full tilt. It causes some of the LED lights in my house to flicker when it happens. I also keep mine down at 24A and it seems to help.
  11. K8QM

    K8QM Active Member

    I'm running at 26A now and in looking back over a little over a month of charging I do see that the first few days when I was running at 30A there was a lot more overshoot or noise (for want of better terms) on the chart and saw that overall when the amount of charge needed was very small the chart is uglier.

    I certainly don't have an explanation except to say that the charging of these giant battery packs made up of lots of little batteries is really quite complex.

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  13. M.M.

    M.M. Active Member

    It's not, really. At least on the AC side, it's just a big, relatively high-voltage AC to DC converter. Nothing exotic or unusual at all, and a hundred or so lithium ion battery cells in series doesn't behave electrically much different than what's in your phone.

    There's a bunch of active temperature control hardware in the battery pack itself, and state-of-charge management logic on the charger end, but fundamentally it's not fancy technology.

    For those commenting on flickering lights and such at higher charge rates, a possible cause is voltage drop due to your main panel or subpanel that is shared with the charger circuit being overloaded, or a borderline breaker, and that would align with higher rates of charge resulting in more misbehavior. Not knowing exactly what kind of conversion circuitry is in the car's charger itself it's possible that there could be high-frequency noise getting injected into the circuit, but I would not expect that if it's decent hardware.

    Or, the flickering could be being caused by the same issue I'm seeing, although in my case there is a clearly audible rattling noise from every affected power supply (which is bizarre) but no affect on any of the LED bulbs or electronics. Let me be absolutely clear that, if my issue is being caused by the car at all (I haven't ruled out the breaker or charger), it is in absolutely no way normal or acceptable. No properly-behaving piece of equipment plugged into a household power circuit should be injecting harmonics capable of doing anything remotely approaching that, and it would be an issue requiring warranty repair.

    That it's very erratic in my case is another oddity. Normally something like that would be completely replicable--shove current through the problem device, it acts up. It also indicates that it's clearly not what it's "supposed" to be doing, or it would do it all the time.
    Regarding full state of charge, a Li-ion pack will generally taper off the rate of charge somewhat when it's approaching full, though I don't know whether that's necessary with the top-end buffer in the Clarity. If so, then a battery that's almost full might see a reduced rate of charge for a few minutes, and depending on how the charger does it (it could be a form of PWM) it could result in some non-flat power curves or interference on nearby devices, but I wouldn't normally expect that, and it's certainly not related to what I'm seeing/hearing.
  14. AlanSqB

    AlanSqB Active Member

    In my case I can vouch for it not being voltage drop. The inverter is noisy. It’s definitely a harmonic of some sort.
  15. K8QM

    K8QM Active Member

    Complex - it's my understanding that in some battery packs individual cells are monitored to make sure no cells are overcharged - so that the charge rate is slowed to accommodate the slowest cells - that may not be the case in the Clarity's pack.

    Flickering lights - I don't get flickering even at 32A, I noticed it on this occasion when the car actually needed very little charge. My voltage is rock solid.

    Rate change - It's hard to see as I can't stretch the hour scale of the chart but the charge rate does drop as charging nears completion. If you look closely at the chart you can see that the trailing edge is not vertical.

  16. M.M.

    M.M. Active Member

    There are packs with internal management like that, but my point is more that technology inside the battery pack isn't relevant to the AC side of the charger. That's just an AC to DC converter with a wide input range and variable current. It shouldn't look appreciably different to the upstream electric system at 10% load than it does at 100% unless it's an incredibly crappy power supply.
  17. M.M.

    M.M. Active Member

    FYI, I finally caught some of the weird noise with a power analyzer, so I can see electrically what's happening now, although I still don't know which component (breaker, charger, or car) is actually causing it. There's only a little noise on the voltage, what's freaking out is the current.

    I'm showing single-phase rather than split phase graphs just because it's easier to see; darker line is voltage, lighter one is current. The current is measured downstream of the breaker on the way to the charger, the voltage is at the bus bars in the panel. Here's what it looks like when it's charging correctly at about 28A RMS (40A peak-to-peak):

    The waveforms are both clean, the power factor is extremely good, and there's virtually no distortion.

    Here's what it looks like when my whole house is rattling:
    There's a bit of noise in the voltage, but the current is a complete mess; it appears that it's exceeding the expected current for some cycles by about 10-20%, then toward the end of the cycle the current drops to zero almost instantaneously for maybe an eighth of a cycle. Sometimes you can see the chopped waveform pick back up at the tail end of the cycle, but as far as I can tell it's always on the trailing edge.

    As for what's causing this, still no idea (but I'm not an expert; going to talk to more knowledgeable coworkers tomorrow and see if they recognize this), and it comes and goes erratically--this time it did it for a couple minutes after I started charging, then stopped and ran smoothly for the remainder of the 2 hours.

    I could see how a flakey/arcing breaker could do this (drop out the current for chunks of a cycle), except that wouldn't explain why the current would be too high for part of a cycle before the arc/dropout. After, I could see it being power electronics in the AC/DC converter surging to pick up after a loss of current, but the current seems to lead the dropouts consistently.

    Getting a voltage tap in somewhere downstream of the breaker next time it's acting up should narrow it down, since a breaker short or arc should be extremely visible. Other possibilities are a flakey contactor in the charger or the AC/DC converter itself freaking out and kicking in some kind of sub-cycle scale overcurrent protection in the power circuitry.
  18. M.M.

    M.M. Active Member

    This is mostly unrelated, but here's a graph of a full charge event from 5% (according to the app; two bars on the dash) to 100% state of charge. I drove until the car dropped out of EV mode (maybe 9% SOC), then parked and turned on the heater and headlights for a few minutes until there was almost no blue left on the power gauge (meaning the ICE would kick on at the slightest provocation), which showed as 5% SOC in the app. The data is collected at 0.25s intervals, so this is going to show a lot more noise than the data logged by most chargers.

    Screen Shot 2018-05-21 at 1.06.26 AM.png

    The noise in the first few minutes is the weirdness described above, where the RMS current is higher than it should be and the waveform is chopped all to heck. This could indeed correspond to the odd glitch at the start of K8QM's charge cycle. Keep in mind that this is in no way a normal part of a charge routine, and it's done this throughout an entire charge cycle starting at around 70% for me.

    The remainder is what it should look like; very stable at about 28A until the last approximately 7.5 minutes, at which point the car ramps down in a curve from 28A to 3A, then turns off. This is again what's showing up at the end of K8QM's graph, and is normal--the car is presumably reducing the charge rate when the battery is almost full. It actually also ramps up at the start as well, but only briefly--it goes from 0A to full load over about 4 seconds.

    Total charge time 2 hours 14 minutes 35 seconds.

    I forgot to turn on real power logging when collecting data, but it looks like the steady-state charge rate is about 6.9kW, with a total power input (subtracting an apparent ~36W of either noise or parasitics from the charger) of about 14.8kWh, actual maybe a hair lower due to the waveform distortion at the start. Using a ballpark charge efficiency of 90% for the battery and 98% for the AC/DC converter, that would mean 13.0kWh to go from 5% to 100% as reported by the app, meaning that 100% capacity according to the app is around 13.7kWh, or 80% of actual 17kWh capacity. That's actually a lot higher than I would expect when you take into account top and bottom end reservations, which makes me wonder if I've got some bad math somewhere.
  19. Rajiv Vaidyanathan

    Rajiv Vaidyanathan Active Member

    I have been having this problem ever since I installed the Siemens L2 Charger. Occasionally, my kitchen lights will flicker annoyingly (the kitchen has all LED lighting). Has been quite frustrating since I had all new wiring put in when I remodeled the kitchen and got a new 50A line put in for the charger. Electrician has no explanation other than to say that LED lighting issues are not uncommon when power draw is large.
  20. Wall-e

    Wall-e Member

    Your voltage is much lower on the second graph vs the first. Seems like your onboard charger trying to either correct for voltage lagging or the voltage sagging. Does this happen when something else is on such as an inductive load?
  21. M.M.

    M.M. Active Member

    That voltage difference is an artifact of the meter graph, not real. The voltage is measured at the busbars of a 100A subpanel off of a 200A main panel; subpanel has maybe 15A continuous load (all electronics) at most apart from this charger, the main panel probably only adds another 10A to that, and during this charge there were no significant inductive loads running in the house.

    The actual line voltages at the subpanel bus are 125.3V (about 0.2V delta from max to min) without the charger running, 119.6V (about 0.5V max to min) with the crazy waveform happening, and a slightly more stable looking 119.5V (also 0.5V max to min) when the charger had stabilized.

    And no; an inductive load starting occasionally induces a tiny flicker in lights, and may occasionally cause a chirp out of the UPSes in the house, but nothing like this.

    Of note, while I can hear whatever harmonics this is inducing in many power supplies throughout the house, there are no visible symptoms in any LEDs (a dozen bulbs from about 6 manufacturers) or the one CFL that's left, although it's possible that a similar thing could cause flicker, which might account for what others have seen.
  22. Vezz66

    Vezz66 Member

    I have the same problem with my LED kitchen lights (120v type), as I just got my Lev2 charger installed last Friday and was away for the weekend. So annoying I had to turn them off, then stopped the charging using the app and the lights stopped flickering (this being the only cause I could think of). Water heater was likely running at that time but nothing much else.

    Those lights are sensitive to something, it's not the first time they flicker like that for unknown reasons, but this was much worse.

    Charger set at 32A, but I will dial down the power if this helps.
  23. Rajiv Vaidyanathan

    Rajiv Vaidyanathan Active Member

    Unfortunately the Siemens charger operates at a fixed 32A. :-(

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