scottf200
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Re: Nissan finally gets it with new 240V portable EVSE

Wed Jan 17, 2018 7:23 am

powersurge wrote:This belongs in a forum about saving electricity... Who cares about any of that chart? We are talking about the EVSE circuit....
Sorry about that. I was just trying to explain the very basics of an electrical panel and circuit board to him since he didn't understand how circuit max vs max input to the panels worked. For people with multiple electric cars in their garage that may be on a subpanel it is an important concept especially as EVs are able to pull larger kW now a days with the larger batteries. i.e. multiple 6.6 kw or 7.2 or Tesla (TM3 9.6kW|240v|40a?) cars. We charge 3 cars in our garage at once on our subpanel and I could easily see 2 as being common for the enthusiast.
100K EV miles and 80% EV usage
Volt = 53+ mile BEV up to 100 MPH, then 40 MPG hybrid with a 9 gal gas tank
'17 Tesla Model X 100D 'used'| RIP '16 P90DL Sig | 2011 Volt kid2 | 2016 for wife | 2012 kid1

cwerdna
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Re: Nissan finally gets it with new 240V portable EVSE

Wed Jan 17, 2018 10:57 am

scottf200 wrote:
powersurge wrote:This belongs in a forum about saving electricity... Who cares about any of that chart? We are talking about the EVSE circuit....
Sorry about that. I was just trying to explain the very basics of an electrical panel and circuit board to him since he didn't understand how circuit max vs max input to the panels worked. For people with multiple electric cars in their garage that may be on a subpanel it is an important concept especially as EVs are able to pull larger kW now a days with the larger batteries. i.e. multiple 6.6 kw or 7.2 or Tesla (TM3 9.6kW|240v|40a?) cars. We charge 3 cars in our garage at once on our subpanel and I could easily see 2 as being common for the enthusiast.

That doesn't past the smell test to me: having a permanent installation that depends on having a vehicle having a means of turning down current drawn at 208/240 volts (vs. what the EVSE's pilot signal advertises) to prevent overload and tripping breakers? As I said, other than the i3 and Teslas, most other EVs don't have any such UI nor should they present such UI.

If the pilot signal from the EVSE advertises, "hey, you can draw 40 amps", the circuit should be able to handle it. It doesn't sound right that there should be caveats. To me, either the EVSE needs be changed to a lower amperage one to prevent overload or turned down (if it provides a means to, which some do (e.g. Tesla's wall connectors)).

Can any electricians or those familiar w/NEC chime in?

'13 Leaf SV w/premium package (owned)
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Please don't PM me with Leaf questions. Just post in the topic that seems most appropriate.

wwhitney
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Re: Nissan finally gets it with new 240V portable EVSE

Wed Jan 17, 2018 11:08 am

If a Tesla UMC defaults to a 40 amp pilot signal when a 14-50 or 6-50 plug is connected to the UMC, and there is no way to configure the UMC to use a 32 amp pilot signal with that plug, then that Tesla UMC should not be plugged into a 40 amp circuit that uses a 14-50 or 6-50 receptacle. This lack of configurability I would consider a design flaw in the Tesla UMC.

However, as a practical matter, the worst that will happen is that the 40 amp circuit breaker will trip. Absent bad installation or other problems, the wiring and receptacle are all capable of 40 amp continuous; the 40 amp circuit breaker is the weak link and may trip on 40 amps continuous. The only real way to do harm in this case would be to continually reset the 40 amp circuit breaker as it trips, since that may weaken the circuit breaker and cause it not to trip when it should.

So for a knowledgeable user to occasionally do this by controlling the maximum current through an EV's interface, rather than through an EVSE with the proper pilot signal, strikes me as a reasonable compromise. If it would be a regular occurence, it would be better to get an EVSE with the proper pilot signal or to use a 50 amp circuit. I'm not a fan of the "nobody is going to use it but me" argument.

Cheers, Wayne

scottf200
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Re: Nissan finally gets it with new 240V portable EVSE

Wed Jan 17, 2018 11:46 am

wwhitney wrote:So for a knowledgeable user to occasionally do this by controlling the maximum current through an EV's interface, rather than through an EVSE with the proper pilot signal, strikes me as a reasonable compromise. If it would be a regular occurence, it would be better to get an EVSE with the proper pilot signal or to use a 50 amp circuit. I'm not a fan of the "nobody is going to use it but me" argument.
Cheers, Wayne

Good point about the circuit breaker being the safety factor in all this.

BTW, in the Tesla whatever you manually change the the amps to at that GPS location it remembers it. i.e. mine stays at 32a in my garage even if I charged at a campground at 40a with the same UMC. ie. If you go to your parents for a long holiday or whatever and they have older home with even 120v receptacles in their garage you can dial it to 9a (or whatever) to be extra safe and it will default to that the next time so you (or spouse) do not have to remember.

I think the Gen II Volts do the same ... remember to stay on 8a if that is what was used at a location before.

On the related threads topic, I wonder if the Gen II LEAFs do GPS/location base remembering for these things.

FYI on warning in the Volt manual:
Volt manual text: Using a charge level that exceeds the electrical circuit or electrical outlet capacity may start a fire or damage the electrical circuit. Use the lowest charge level until a qualified electrician inspects the electrical circuit capacity. Use the lowest charge level if the electrical circuit or electrical outlet capacity is not known.

FYI on Tesla manual on its lowering amperage button AND the builtin safety detection:
Tesla manual text: The current [amperage] automatically sets to the maximum current available from the attached charge cable, unless it was previously reduced to a lower level. If needed, touch the up/down arrows to change the current (for example, you may want to reduce the current if you are concerned about overloading a domestic wiring circuit shared by other equipment).

It is not possible to set the charging current to a level that exceeds the maximum available from the attached charge cable.

When you change the current, Model X remembers the location. So if you subsequently charge at the same location, you do not need to change it again. Note: If Model X automatically reduced a charging location's current because of f-luctuations in input power (see the note in Charging Status on page 143), Tesla recommends charging at the lower current until the underlying problem is resolved and the charging location can provide consistent power.

Note: If Model X is charging and detects unexpected fluctuations in the input power, it automatically reduces the charging current by 25%. For example, a 40 amp current is reduced to 30 amps. This automatic current reduction increases robustness and safety in situations when a problem exists outside of Regular maintenance is the key to ensuring the continued reliability and efficiency of your Model X.
Last edited by scottf200 on Wed Jan 17, 2018 7:43 pm, edited 3 times in total.
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Re: Nissan finally gets it with new 240V portable EVSE

Wed Jan 17, 2018 12:39 pm

scottf200 wrote:
wwhitney wrote:So for a knowledgeable user to occasionally do this by controlling the maximum current through an EV's interface, rather than through an EVSE with the proper pilot signal, strikes me as a reasonable compromise. If it would be a regular occurence, it would be better to get an EVSE with the proper pilot signal or to use a 50 amp circuit. I'm not a fan of the "nobody is going to use it but me" argument.
Cheers, Wayne

Good point about the circuit breaker being the safety factor in all this.

BTW, in the Tesla whatever you manually change the the amps to at that GPS location it remembers it. i.e. mine stays at 32a in my garage even if I charged at a campground at 40a with the same UMC. ie. If you go to your parents for a long holiday or whatever and they have older home with even 120v receptacles in their garage you can dial it to 9a (or whatever) to be extra safe and it will default to that the next time so you (or spouse) do not have to remember.

I think the Gen II Volts do the same ... remember to stay on 8a if that is what was used at a location before.

On the related threads topic, I wonder if the Gen II LEAFs do GPS/location base remembering for these things.


I would be shocked, the LEAF features are pretty basic.
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MikeD
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Re: Nissan finally gets it with new 240V portable EVSE

Wed Jan 17, 2018 10:00 pm

wwhitney : Does your just previous post apply as written if the 40a (CB) circuit to the 14-50 receptacle is wired with NM-B 8/3 cable?

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Nubo
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Re: Nissan finally gets it with new 240V portable EVSE

Wed Jan 17, 2018 10:55 pm

wwhitney wrote:However, as a practical matter, the worst that will happen is that the 40 amp circuit breaker will trip. ...


I'd say the worst that might happen is that the 40 amp circuit breaker doesn't trip.

I'm not sure how load calculations are derived for subpanels but it seems reasonable for a subpanel dedicated to 240V devices, the concurrent load of those devices should not exceed the rating. It's entirely reasonable to suppose that both cars will be charging at the same time and for long periods. This is different than whole house loads where obviously most branch circuits are nowhere near capacity at any given time. Adding the loads is how our electrician handled our garage subpanel which feeds the whole-house AC and the EVSE. The subpanel is 60 amps; the AC breaker is 40 amps and EVSE breaker is 20 amps (I use a 16A EVSE). He advised no further load be put on that subpanel. I.e., a 40A or even a 30A circuit for the EVSE was not allowed.

Circuit breaker is there to protect you but shouldn't be used as a crutch, imho. And a vehicle's optional settings is not a substitute for adequate wiring design. Well that's my theory. Hopefully an actual electrician will come along and correct us :)
I noticed you're still working with polymers.

wwhitney
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Re: Nissan finally gets it with new 240V portable EVSE

Wed Jan 17, 2018 11:12 pm

Nubo wrote:I'd say the worst that might happen is that the 40 amp circuit breaker doesn't trip.

No, you're missing my point. The only part of a (properly installed) 40 amp circuit that isn't rated for 40 amps continuous is the circuit breaker itself. The breaker may be "overly protective" in the case of a continuous load. To deal with this requires upsizing the breaker, but then the conductors have to be upsized as well, since the breaker is not "overly protective" for other load profiles.

Nubo wrote:Adding the loads is how our electrician handled our garage subpanel which feeds the whole-house AC and the EVSE. The subpanel is 60 amps; the AC breaker is 40 amps and EVSE breaker is 20 amps (I use a 16A EVSE). He advised no further load be put on that subpanel. I.e., a 40A or even a 30A circuit for the EVSE was not allowed.

That's the wrong way to do the calculation. Motors and HVAC equipment can use breakers that are rated higher than the actual steady state current draw, to deal with high startup current. The HVAC system should be marked with a Minimum Circuit Ampacity (MCA) and a Maximum Overcurrent Protection (MOC), where MCA < MOC. You can use the MCA value to size the conductors and I believe for the load calculation on the panel, but install a breaker anywhere up to the MOC. So if the HVAC MCA is under 30A, you could use a 30A EVSE circuit for a 24A pilot signal EVSE, along with a 40A breaker for the HVAC, all in a panel fed by a 60A feeder.

Cheers, Wayne

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Nubo
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Re: Nissan finally gets it with new 240V portable EVSE

Thu Jan 18, 2018 10:06 am

wwhitney wrote:No, you're missing my point. The only part of a (properly installed) 40 amp circuit that isn't rated for 40 amps continuous is the circuit breaker itself. The breaker may be "overly protective" in the case of a continuous load. To deal with this requires upsizing the breaker, but then the conductors have to be upsized as well, since the breaker is not "overly protective" for other load profiles.


I see your point. Sorry, I was being lazy and didn't read carefully enough and was responding to the general idea of manually setting a car's amp draw on a regular basis to avoid overloads.

Your HVAC info is interesting. Maybe I can get a cheap upgrade after all. I did have them wire the EVSE run with 10-gauge :)
I noticed you're still working with polymers.

scottf200
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Re: Nissan finally gets it with new 240V portable EVSE

Thu Jan 18, 2018 12:38 pm

Nubo wrote:It's entirely reasonable to suppose that both cars will be charging at the same time and for long periods. This is different than whole house loads where obviously most branch circuits are nowhere near capacity at any given time.

That is a solid point. Nice info by @wwhitney about the EVSE pilot signal draw and different HVAC criteria. Great input and discussion related to EVSEs.

Pilot Signal Interface
The pilot signal interface, which Section 3 covers in further detail, requires a 1-kHz, ±12-V PWM signal to
be transmitted down the length of the charger cable to the vehicle. The duty cycle communicates the
power capability of the EVSE to the vehicle. The EV returns its current state by placing a load on the line,
which causes a voltage drop.
To facilitate this, the design requires an amplifier with a wide dual-rail
voltage input and sufficient drive strength to facilitate the various line impedances. This design has
selected the OPA171 amplifier based on its input range characteristics (up to ±18 V) and ability to handle
various line impedance changes, even non-resistive changes in the event of cable parasitics.
via: http://www.ti.com/lit/ug/tidub87/tidub87.pdf

Image
via: https://energy.gov/sites/prod/files/201 ... 2014_p.pdf
100K EV miles and 80% EV usage
Volt = 53+ mile BEV up to 100 MPH, then 40 MPG hybrid with a 9 gal gas tank
'17 Tesla Model X 100D 'used'| RIP '16 P90DL Sig | 2011 Volt kid2 | 2016 for wife | 2012 kid1

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