Lately I've been charging my 2018 Prime from a different GFCI receptacle than the one I usually use. The GFCI has been tripping after about an hour of charging. Every time I reset it, it will charge for another hour or two then trip again. And in fact I have two identical (and independent) GFCIs side by side, and the same thing happens with both. I could just replace the GFCI, but I wasn't satisfied with that. So I decided to measure the ground current from the EVSE back to the wall while charging. It's over 5mA, which is right in the 4-6mA range where a GFCI should trip. This suggests the GFCI is working normally, and the car or the EVSE has excessive leakage current to ground while charging. Interestingly the meter is showing 26.62kHz, not 60Hz as I expected. So maybe this current is from a switching converter in the car's onboard charger? Without an oscilloscope it's hard to say. Also, I'm not sure if the meter measures true RMS, but either way if it's a pulsed waveform, a reading with a meter doesn't give much info. So why does it charge for an hour or two? Maybe the GFCI becomes more sensitive as it heats up, or maybe the leakage increases as electronics in the car heat up. I made this measurement with line and neutral going through an old lamp cord that quickly got hot, so I can't leave it for more than a minute. Why do other GFCIs work? My only guess is they have more filtering and don't respond to this 27kHz current the same way. These GFCIs I'm currently using also trip half the time I turn on my table saw, which I haven't experienced with other GFCIs. They are some old (10 years?) GE GFCI receptacles that came with the house. I haven't had any issues with false tripping from Leviton or Eaton receptacles that I've bought new. The only other possibly related symptom is that the car sometimes doesn't charge at public charging stations. It will either not charge at all, or stop charging randomly, with no useful error from the car or the station. I just assumed they are broken/unreliable, but maybe it's actually the car? I think I did see a ground fault error or something like that on the display in the car once or twice in the time I've owned it, but I don't remember exactly what that said. It isn't showing that error now. The car is well isolated by its rubber tires, so there's no other path for current to ground besides the ground wire in the EVSE. Has anyone else seen GFCI tripping while charging? I'm using the factory EVSE. It would be interesting to try a different one, but they are pretty simple so I don't think the EVSE is the problem. The easiest solution is still to replace the GFCI or use a non-GFCI circuit, and that's eventually what I'll do. Without reverse engineering the onboard charger, I don't think I can find or fix the source of this leakage current.
daughter had the same problem with a washing machine, works fine on a regular outlet. it's frustrating because the only answer seems to be replace the washer
It just might be the GFCI outlets reached their life expectancy. I’ve read somewhere 10-15 years is the expected replacement interval.
Have you checked for other loads on that secondary GFCI circuit? The effects are cumulative, some other load in that same circuit could be contributing to the tripping of that outlet. If this is the case, changing the GFCI would have no effect it's doing what it suppose to do.
The garage has two receptacle circuits, each with only a single GFCI, nothing else downstream or upstream, and no other receptacles on those circuits. The GFCIs are old. I know they don't last forever, but I've usually only seen them fail to trip. Haven't seen one become too sensitive until now. I replaced one GFCI, and as expected it works fine with the new one. Doesn't change the fact that I measured greater than 5mA on the ground pin of the EVSE. I still think the car has marginally high leakage current, but it happens to work on most GFCIs.
Great to hear you figured it out... FWIW; circuit breakers and GFCI are supposed to be engineered so they fail in the open position. Better an open circuit than burning down a house - due to an overload. Most kitchen appliances are designed to draw less than 13A and modern houses usually run 20A circuit breakers to the kitchen. No more than two duplex circuits per kitchen run; when I was doing work for Habitat for Humanity.
Agreed , some friend electrician tells me that since GFI became mandatory , he replaces a lot of GFIbreakers over 7 years old...good extra income for him , like he says : with age some people have a shorter temper so does GFI
I'm having exactly this same experience of GFCI trippinng after 1 - 2 hours of charging our 2018 Prius Prime. But in my case the GFCI in question is brand new, recently installed in the garage of a 30-year-old house we just moved into. We never had this problem at our previous house, where we also charged off a GFCI-protected outlet in the garage. In between the two houses, the car was never charged for around 8 months, because we were living at a rental with no charging outlet available. Is it possible/likely that either the car or EVSE/cable developed some defect over those months that would account for this? I have some reason to question the competence of the electrician who installed our new outlets, so will soon call another person to evaluate and try to fix this.
Get one of those 3 lamp outlet testers from amazon or Walmart. Check to see if it's connected properly. If it's OK; pop the circuit and see what outlets goes out in your house. A lot of times, electricians will daisy-chain a single GFCI outlet up to a bathroom or kitchen - someplace it's required by local building codes. Other appliances on the same circuit, may pop your GFCI, cumulative leakage current across multiple appliances. Make sure everything is off or unplugged on that circuit, while the car is charging or switch to another circuit. That big black brick in your charging cable is also a ground fault interrupt. Hope this helps
I had a problem, but it was a GFCI breaker tripping because the freezer in the garage was kicking on in the middle of the night when the car was trying to charge. Obviously not the same problem as you're having, but I dropped the charge mode from the maximum (12 amp) to the 8 amp charging mode. If you can take going from 6 hours to 8 hours to charge the car, maybe this will help. Do you have a different charger you could borrow to try?
Just fyi the prime can draw either 8 or 12 amps, it’s switchable in the car’s settings menu. I had two primes charging on the same circuit and it kept tripping ;-)
