Remote control of EVSE using circuit breaker: Any concerns?

Occasionally I will terminate charge using the dedicated circuit breaker for the 240V outlet where the Panasonic EVSEupgrade unit is plugged in. This is more convenient than going out into the cold garage to unplug the unit and it allows me to also restart charging without going back out into the garage. I find that I use this approach more frequently in the wintertime and I am considering using this approach once our CarWings subscription expires.

But since I imagine the interlocking mechanism between the EVSE and the EV is more eloquent than simply disrupting power, I thought I would ask if there are additional stresses induced by this practice that could damage the EVSE, the OBC in the LEAF or both. For instance, if the breaker is switched off at the peak voltage during charging, the inductive spike (either positive or negative) which appears at the input to the EVSE and hence the OBC could be quite high. So here are a few questions:

1) Do the EVSEupgrade unit and the OBC in the LEAF both have voltage suppression circuitry at their inputs to protect them from potential damage from spikes caused by circuit breaker disruptions?

2) If 1) is true, and I assume it is, how much current and wire length (or inductance) are these units designed and tested to handle? (For reference, our outlet is wired using 10-3 Romex and it is about 140 wire feet from the breaker panel, one way, or 280 feet round trip.)

3) Assuming the units are protected against catastrophic failures due to this type of event, does toggling the breaker induce any sort of repetitive stress on the EVSEupgrade or LEAF OBC that could lead to reduced equipment life?

4) What is the expected cycle life of a circuit breaker used in this manner?

5) Since others may be using this approach at higher currents with other EVs, does this approach get more and more problematic at higher charging currents?

6) Are there any other issues that I should consider regarding initiating and terminating LEAF charging using the circuit breaker for the EVSE?

Of course I am interested to hear Phil's thoughts on this since he designed and tested the EVSEupgrade unit, but I am also interested in hearing any discussion from others on this topic, as well. TIA!

RegGuheert said:

4) What is the expected cycle life of a circuit breaker used in this manner?

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I'd think the repeated arcing in the circuit breaker would be reason enough to not do this. You're going to end up with very poor contacts.

richard said:

RegGuheert said:

4) What is the expected cycle life of a circuit breaker used in this manner?

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I'd think the repeated arcing in the circuit breaker would be reason enough to not do this. You're going to end up with very poor contacts.

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I see some references to UL489 testing with 6000 full-load cycles. I doubt I would do this more than about 100 times each year. That would be about 2000 cycles in 20 years. It sounds as if the breaker will outlive the LEAF.

The problems with blowing OBCs with GE Wattstations (although it's happened with other brands as well) has been blamed by GE on bugs in the OBC related to power outages, spikes or low-voltage situations. Seems imprudent to cause power outages and spikes on purpose.

The only really safe way to interrupt charging is to get the car
to stop drawing current, which is only available now by pressing
the unlatch (proximity switch) on the J1772 handle.

It would be possible to program the EVSE to reduce the Pilot signal
to a very low "error" duty cycle, which should signal the car
to quit charging. However, I have not yet heard of this feature
being implemented in any EVSE.

Some J1772 cables bring the Proximity signal back out to the EVSE,
so a "Stop Charging" button on the EVSE could load that line
to simulate the Proximity switch being pressed.

How you load the Proximity line depends upon where the blue wire
comes from, usually pin 5 of the J1772 plug,but check that, because
it could be from the "top" of the Proximity Switch, or even not connected.

http://code.google.com/p/open-evse/wiki/J1772Basics" onclick="window.open(this.href);return false;

Shows a basic schematic of the Pilot and Proximity.

davewill said:

The problems with blowing OBCs with GE Wattstations (although it's happened with other brands as well) has been blamed by GE on bugs in the OBC related to power outages, spikes or low-voltage situations.

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I thought the GE problems were related to brownout (low voltage), but perhaps the other issues are involved.

davewill said:

Seems imprudent to cause power outages and spikes on purpose.

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Agreed, in general. But I find myself doing this sometimes in the early morning, so I assume others might also be doing this. OTOH, I would imagine someone with an EVSE that meters electricity or has an internet connection would not turn off the unit from the breaker as I am doing.

RegGuheert said:

davewill said:

The problems with blowing OBCs with GE Wattstations (although it's happened with other brands as well) has been blamed by GE on bugs in the OBC related to power outages, spikes or low-voltage situations.

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I thought the GE problems were related to brownout (low voltage), but perhaps the other issues are involved.

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GE Statement said:

http://www.ge-energy.com/leaf-wattstation-facts.jsp

Nissan and GE have completed their investigation into the instances of Nissan LEAFs experiencing on-board charging (OBC) issues when using certain EV chargers. Nissan has traced the root cause of the issue to the LEAFs OBC software that can allow damage to occur to its OBC components while using certain chargers and in certain instances, such as when a brief under voltage or blackout condition occurs. Nissan is working to address this issue as quickly as possible, and in the meantime is advising customers to avoid charging during times when brownouts or momentary power dips may be likely, such as during electrical storms or high power usage on the grid.

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Yeah, it seems to be brownout or momentary blackouts. I still wouldn't do it, personally. Have you thought of setting up your timer for, say, 2AM to 6PM, so that it turns itself off in the evening?

garygid said:

The only really safe way to interrupt charging is to get the car
to stop drawing current, which is only available now by pressing
the unlatch (proximity switch) on the J1772 handle.

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I wondered how this was done. I have always *expected* that pressing the button on the handle of the EVSE would interrupt charging, but I will say that with our EVSE and LEAF this does NOT happen. I just tried it again and I can hold that button down as long as I like and the LEAF keeps charging. So there is a proximity switch inside which causes the OBC to stop drawing current before the connector is fully disengaged?

Also, I hope that the pins for the pilot are shorter than those for the power so that the pilot disappears and current stops before I could break the flow of current. (Perhaps that is how proximity is determined?)

garygid said:

It would be possible to program the EVSE to reduce the Pilot signal
to a very low "error" duty cycle, which should signal the car
to quit charging. However, I have not yet heard of this feature
being implemented in any EVSE.

Some J1772 cables bring the Proximity signal back out to the EVSE,
so a "Stop Charging" button on the EVSE could load that line
to simulate the Proximity switch being pressed.

How you load the Proximity line depends upon where the blue wire
comes from, usually pin 5 of the J1772 plug,but check that, because
it could be from the "top" of the Proximity Switch, or even not connected.

http://code.google.com/p/open-evse/wiki/J1772Basics" onclick="window.open(this.href);return false;

Shows a basic schematic of the Pilot and Proximity.

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Thank you for those details and the link. It gives me a much better idea of what is going on when I withdraw the handle. But it does seem to me that there are a lot of deviations among J1772 implementations in the wild. It almost seems like the RS232 of EVs.

I would make the effort to go out and unplug the J handle and not use the breaker. If it is that cold then sitting at 80% or even 100% can't be a big deal.

davewill said:

Yeah, it seems to be brownout or momentary blackouts.

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Of course contact bounce can look like a *very* brief blackout. I don't know how often contacts bounce upon breaking. I suppose it would be possible to have the breaker slip off your thumb and create a momentary blackout inadvertently.

davewill said:

I still wouldn't do it, personally.

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Yeah, it does carry a certain amount of risk.

davewill said:

Have you thought of setting up your timer for, say, 2AM to 6PM, so that it turns itself off in the evening?

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Currently, we have an end timer set for 80%. The thing is, our SOC before the charge is all over the map, so none of the modes provided really suit us. Hopefully LEAFscan will allow us to terminate at 65%, if desired.

smkettner said:

I would make the effort to go out and unplug the J handle and not use the breaker.

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Agreed that is the best practice today.

An even better practice would be for Nissan to offer a remote (or even an in-car) "terminate charge" command. Such a command would prevent the need for an EVSE withrawal and reinsertion.

smkettner said:

If it is that cold then sitting at 80% or even 100% can't be a big deal.

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Agreed. But we are trying to eek out the most battery life so that we can to minimize cradle-to-grave costs. Today I switched off the EVSE from the breaker to limit SOC and right now the temperature has risen to 71F.

I do not recommend you ever interrupt power to an EVSE while charging by any means other than by disconnecting the handle first! By flipping the breaker, you probably won't hurt the EVSE, but the Leaf's OBC has been proven to be sensitive to arcing, surges, and sags. The breaker will most definitely be exposed to arcing which will shorten it's life and could result in a failure. The charging system is designed such that on proper termination there is zero current flowing before any switches or contacts open.

The button most definitely does drop the power to zero. There is no indication that this is happening, no noise, no lights, but if you monitor the current (have someone watch your electric meter) you will see that it instantly does drop the power to zero. Only upon removal of the handle does it change any status indicated on the car/EVSE.

If you wanted to add a remote control interrupt to the Leaf's charging system, it could be done safely, but the best way is to use the existing timer functionality built in to the Leaf already. Have the timer stop the charge at a certain time or 80%, and you can always restart it in the house from Carwings.

-Phil

Ingineer said:

I do not recommend you ever interrupt power to an EVSE while charging by any means other than by disconnecting the handle first! By flipping the breaker, you probably won't hurt the EVSE, but the Leaf's OBC has been proven to be sensitive to arcing, surges, and sags. The breaker will most definitely be exposed to arcing which will shorten it's life and could result in a failure. The charging system is designed such that on proper termination there is zero current flowing before any switches or contacts open.

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O.K. I will mend my wicked ways and will limit charging interruptions to the handle.

Ingineer said:

The button most definitely does drop the power to zero. There is no indication that this is happening, no noise, no lights, but if you monitor the current (have someone watch your electric meter) you will see that it instantly does drop the power to zero. Only upon removal of the handle does it change any status indicated on the car/EVSE.

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Thanks for telling me that! I will certainly test this out further!

Ingineer said:

If you wanted to add a remote control interrupt to the Leaf's charging system, it could be done safely, but the best way is to use the existing timer functionality built in to the Leaf already. Have the timer stop the charge at a certain time or 80%, and you can always restart it in the house from Carwings.

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Thanks! But I intend to push Nissan on this point. Having to make two extra trips to the car and adding a fully insertion/withdrawal cycle of the EVSE handle to stop and restart charging is quite an annoyance!

RegGuheert said:

Ingineer said:

The button most definitely does drop the power to zero. There is no indication that this is happening, no noise, no lights, but if you monitor the current (have someone watch your electric meter) you will see that it instantly does drop the power to zero. Only upon removal of the handle does it change any status indicated on the car/EVSE.

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Thanks for telling me that! I will certainly test this out further!

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Well, just as you said, the charging current drops to zero when the EVSE handle button is pressed. But it really fooled me! There is ABSOLUTELY no clue from the LEAF or the EVSE that any change has occurred!

This is good to know. Frankly, I had always wondered if the charging current was interrupted and therefore I was concerned that arcing was happening between our $1000 EVSE and our $35,000 EV. That incorrect belief is one reason I thought throwing the breaker would be O.K. In fact, I thought it might be better because I would rather replace the breaker than the EVSE or the car. Thanks again for setting me straight on this!

There is no problem tripping breaker to stop charging - except breaker wear. The EVSE sees a power fail and commands the EV to stop charging - no stress on the EV at all.

maxmike said:

There is no problem tripping breaker to stop charging - except breaker wear. The EVSE sees a power fail and commands the EV to stop charging - no stress on the EV at all.

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Wrong

When breaking current in a circuit breaker, an arc forms, and the voltage potential between the breaker contacts becomes large. The arc itself has an inductive reactance which attempts to maintain current through the zero crossing. This results in high voltage spikes which can travel downstream and hurt your precious EV. The EVSE has no means to stop these spikes, as they occur relatively quickly, and the EVSE is not monitoring voltage that closely as it is ground fault currents. The spikes are not normally super large, but you are putting your EV at risk by doing this. The breaker is meant to break fault current and safely shut down miss-operating equipment, not to act as a regular switch.

Source: I work with breakers in the thousands of amps range. On very large breakers, a phenomena known as "restrike" can occur where the high voltage across the contacts and the lingering ionic gas allow the arc to reestablish itself, and the breaker fails to clear the fault.

The CarWings App needs a "STOP Charging" feature :roll: