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Joined: Mon Feb 04, 2019 4:44 pm
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Re: 30A Circuit Breaker tripped on Nissan Leaf

Mon Feb 04, 2019 5:16 pm

Hi Guys, I have a circuit breaker that has been constantly tripping when charging my Leaf. I "appear" to have found the issue and I thought I'd share it here:

Conclusion: Put simply, the onboard charger of the Leaf draws X Watts of power (depending on the level of charge). The Voltage supplied by the power company 'appears' to drop. Power = Current x Voltage, thus as the Voltage drops the onboard charger draws more Current to keep the overall Power as constant as possible. As the Current increases, the 'charger' unit on you wall detects a higher than acceptable Current and automatically shorts the circuit to trip your cicuit breaker.

This problem appears to occur when there is, in my case, a very cold spell and everyone in my neighbourhood, turns on more electricity. Once the cold spell is over, the Voltage returns to a more acceptable range and there is no longer any circuit breaker trips.

This is my sense of the issue and I could be wrong.

Observation: I have a 50amp Level 2b charge setup and found my circuit breaker tripping on a constant basis almost after a minute of being set. I opened the charger on the wall (please don't do this unless you have an electrical background). I measured the voltage in the system and found that the voltage had dropped well below 190Volts (was at about 185V). The voltage in my part of the world should be 204Volts (you read right - not 240 but 204). I temporarily upgraded my circuit breaker to 60amps (please don't do this) and felt the temperature of the cable, it did not get hot, as the voltage dropped the Current spiked (I believe). And the charger unit on my wall triggered a short to trip the 60amp breaker. (ie: a larger breaker will not solve the problem).

Today the Voltage is between 194V and 201V and today I have no circuit breaker trips, the car has charged well and the wiring has not gotten hot. This appears to be within the accpetable range of my wall charger unit's electronics. Thus the only pattern I can ascertain is the Voltage dropped too low, the car compensated by drawing more Current and the charger on the wall said, "No". Is there something that could be done?

Well my 110VAC L1 charger did work while the L2 charger was tripping the system. It's not ideal, but switching to the L1 charger temporarily may be the only short term solution.

I have been researching this topic, I see there is a single signal wire coming from the car. According to J1772 protocol this is a 12VDC signal wire and I will take some measurement from this wire IF I have the problem again.

I also came across this YouTube video (that scares me a little) but is VERY helpful and if I come across any more issues, I will definitely post my observations, etc. Here is the video:

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Re: 30A Circuit Breaker tripped on Nissan Leaf

Mon Feb 04, 2019 6:51 pm

That doesn't make much sense. Regardless of the voltage sag, the LEAF won't draw more than the amperage the EVSE advertises. Do you have a 50a EVSE on a smaller circuit?
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Re: 30A Circuit Breaker tripped on Nissan Leaf

Mon Feb 04, 2019 7:38 pm

I tend to agree. The EVSE broadcasts the power available via the pilot. The car respects that and does not ever exceed it; A 30A EVSE would normally charge the Leaf at 27.5A Ithe car will never exceed 30A. The pilot signals the current by varying the duty cycle of the square wave. 30A is totally symmetrical. It is a special case. All other currents vary the duty cycle.

It is possible that you have a 40A EVSE but why. The car sets the charging current fi there is enough. A Leaf will charge the same from a 30A or the spec max 80A. Just more current is not used..
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