EVSE source current

LTLFTcomposite said:

AndyH said:

Too many guess without facts, gents! ...
Andy

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We think we know that the "emergency" 120v cord plugs into the J1772 connector. But do we know if it actually does pilot signaling or does the car just have some default behavior when 120 volts appears on the pins unannounced? (eg start suckling at 12 amps) And if so, what is there a similar behavior in Europe, but at 240volts?

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Per the J1772 spec, any EVSE MUST provide a pilot signal. The spec is clear about what the EVSE sends to the car and how the car responds. It's back in post 2 - but posted again here.

This from June 19th...
http://www.mynissanleaf.com/viewtopic.php?p=7751#p7751

I have a copy of the J1772 recommended practice from Jan 2010. I haven't yet played with any hardware designed to use this standard, so cannot say how EVSE manufacturers are actually using the info in the J1772 doc.

According to the document, the Control Pilot signal performs multiple functions. It allows the EVSE to properly detect that a vehicle is connected. The EV receives a signal that the EVSE is ready to supply energy. The EVSE is notified if the charge area needs ventilation. Finally, the EVSE signals the EV, by modulating the pilot duty cycle, to communicate the maximum available continuous current capacity.

5.3.5.1 IF the EV/PHEV reads a duty cycle of 3-7%, the EV/PHEV shall interpret this as a valid digital communications command.

5.3.5.2 IF the EV/PHEV reads a duty cycle between 8% and less than 10%, the EV/PHEV should interpret this as a valid 10% duty cycle.

5.3.5.3 IF the EV reads a duty cycle less than or equal to 85.0% the EV/PHEV should base the current on the Amps = (% duty cycle) * 0.6 formula.

5.3.5.4 If the EV reads a duty cycle greater than 85.0%, the EV/PHEV should base the current on the Amps = (% duty cycle - 64) * 2.5 formula.

5.3.5.5 IF the EV reads a duty cycle of 97%, it is recommended the EV/PHEV consider this as a valid 96% duty cycle.





Bottom line - if the car is in compliance with the CURRENT J1772, it cannot charge without a pilot signal of some type. Either the car will receive a pilot signal between 10 and 97% to set the proper current limit, or it will receive a 5% pilot signal and know to listen for more instructions on the digital data signal (not the same as the pilot signal) (and not yet defined as that's in another SAE standard).

Note again the lines on table 6B for signals below 3%, between 7 and 8%, and over 97% - Error state , no charging allowed. No pilot = error state and charging cannot start.

Hypothetical detour...
We could guess that Nissan has found a way to be J1772 Jan 2010 compliant while allowing a straight extension cord connection for a 120V emergency charge. If they did that, and since they're supplying the 120V EVSE, and since they would have a larger profit if they could provide a 'dumbed-down' EVSE product, why would they include a full EVSE in the trunk bag rather than a $5 extension cord with a J1772 connector?

Then there's the down-side risk of shock (no EVSE means that the hypothetical hacked emergency cord would have live terminals when it's connected to 120V - illegal for J1772) and legal action from the 'unsafe' connection when clearly 'safe' products are available and in full compliance with J1772. I really don't think they'd take that risk.

Andy

edit...typo...$5 vice %5

The J1772 description of Control Pilot signaling (levels, frequency, PWM) applies to both L1 and L2 EVSEs and compliant vehicles.

So, no non-pilot defaults are described.

garygid said:

Charger AC current Requirement Example:

An efficient charger with a 120v AC input, putting 21 amps into a 75 volt (21 cells x 3.5 volts = 73.5 volts) battery makes about (21 x 75 = 1575 watts) of DC output.

So, the (maybe 94%) efficient (probably "switching" type) charger might draw about 14 amps (120 x 14 = 1680 watts) from the AC lines?

And, perhaps a little less if one actually has 124v AC instead of 120v?

That might explain why a 15-amp breaker does not "pop" when doing "21-amp charging".

Maybe my numbers are not perfect, but the general idea still holds.

Having 16 amps "allowed" gives us an extra 33% over the power we "are allowed" with the 12-volt max limit. So, 20-hour charging would drop to about 15 hours, and a "half" charge of 10 hours would drop to only about 7.5 hours ... possibly suitable for really useful 120v charging while at work.

Click to expand...

Now do the math when I connect the ElCon '1500W' that's actually pulling 14A to the top of the 15A outlet and connect the Thunder Sky '60/15' that's pulling 13A from the bottom of the same outlet, please.

A 15A breaker, depending on temperature, can move close to 30A before tripping.

AndyH said:

Too many guess without facts, gents! ...
...
...
I expect that it'll be less expensive to put a dryer cord on our AV L2 EVSE than buy a device from another company or import one from Europe or the Far East. The quotes I'm getting for L1 and L2 EVSE are more than twice what AV is getting for their L2 device - unless we can find something less expensive, AV is still the way to go.

Andy

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But changing Nissan's 120V *included* ("free") emergency L1 EVSE to pull the same 12A at 240V would be even cheaper while cutting charge-time in half.

garygid said:

The J1772 description of Control Pilot signaling (levels, frequency, PWM) applies to both L1 and L2 EVSEs and compliant vehicles.

So, no non-pilot defaults are described.

Click to expand...

I'm not sure I understand what you're trying to communicate here, Gary.

"no non-pilot defaults are described"

The Jan 2010 J1772 spec clearly defines the full range of pilot signals created by the EVSE and sent to the car, as well as the required response from the car.

A 'non-pilot' situation might mean the wiring is connected but the duty cycle is 0%. It could also mean that there is no pilot line connected. Let's look at both scenarios from the perspective of the spec.

Valid wiring, 0% duty cycle.
This is clearly explained in Table 6A on page 16.
From the EVSE perspective: Duty Cycle < 5% is an Error State - No Charging Allowed
From the car perspective: Duty cycle < 3% Error State - No Charging Allowed

Invalid or incomplete wiring.
The car and EVSE share three lines to communicate switches and the pilot - ground, the pilot signal line, and the 'proximity switch on the EVSE connector is closed' line. All three must be present for charging to begin. If one or more of the three lines is not connected, the EVSE control box is not able to close the power contactor to feed AC to the charger. If the proximity switch (confirmation that the charge connector is seated and latched into the car) isn't closed, the car's charge controller does not close it's 'ready' switch (communicates ready status to the EVSE) and doesn't activate the car's charger. (See pages 11 thru 16.)

LEAFer said:

AndyH said:

I expect that it'll be less expensive to put a dryer cord on our AV L2 EVSE than buy a device from another company or import one from Europe or the Far East. The quotes I'm getting for L1 and L2 EVSE are more than twice what AV is getting for their L2 device - unless we can find something less expensive, AV is still the way to go.

Andy

Click to expand...

But changing Nissan's 120V *included* ("free") emergency L1 EVSE to pull the same 12A at 240V would be even cheaper while cutting charge-time in half.

Click to expand...

If the 'EVSE Guts' can handle the increased current then absolutely - the price is right for this option!

Sorry, I meant "no USEFUL non-pilot...".
Thus, no useful "trivial" EVSE substitutes.

AndyH said:

LEAFer said:

AndyH said:

I expect that it'll be less expensive to put a dryer cord on our AV L2 EVSE than buy a device from another company or import one from Europe or the Far East. The quotes I'm getting for L1 and L2 EVSE are more than twice what AV is getting for their L2 device - unless we can find something less expensive, AV is still the way to go.

Andy

Click to expand...

But changing Nissan's 120V *included* ("free") emergency L1 EVSE to pull the same 12A at 240V would be even cheaper while cutting charge-time in half.

Click to expand...

If the 'EVSE Guts' can handle the increased current then absolutely - the price is right for this option!

Click to expand...

You mean increased VOLTAGE (not current) ...

LEAFer said:

AndyH said:

If the 'EVSE Guts' can handle the increased current then absolutely - the price is right for this option!

Click to expand...

You mean increased VOLTAGE (not current) ...

Click to expand...

Well... Will you accept yes and no? :lol:

Sorry...I answered the question thinking about using an assumed 120V 12A EVSE for 120V 16A. :?

The EVSE appears to use a separate power supply of a bit over 12VDC. We might want to check that before connecting to 240V. We may have to provide our own separate 12V source.

AndyH said:

The EVSE appears to use a separate power supply of a bit over 12VDC. We might want to check that before connecting to 240V. We may have to provide our own separate 12V source.

Click to expand...

Are you surmising ... in the guts of the (simplified) emergency EVSE they assume 120V AC input, and use that to create 12VDC (and possibly 5VDC) to power the micro-controller ? Hmmm ... yes that could present a problem. (I was hoping for zero mods of the guts.) So, unless they design the US, Euro and Japanese versions input voltage tolerant and with PSU components that auto-adjust ...

The EVSE probably needs "-12" as well as the "+12" DC supply.

LEAFer said:

AndyH said:

The EVSE appears to use a separate power supply of a bit over 12VDC. We might want to check that before connecting to 240V. We may have to provide our own separate 12V source.

Click to expand...

Are you surmising ... in the guts of the (simplified) emergency EVSE they assume 120V AC input, and use that to create 12VDC (and possibly 5VDC) to power the micro-controller ? Hmmm ... yes that could present a problem. (I was hoping for zero mods of the guts.) So, unless they design the US, Euro and Japanese versions input voltage tolerant and with PSU components that auto-adjust ...

Click to expand...

Most 12v supplies are universal, if there is GFI then it will have more to do with that component.

LEAFer said:

AndyH said:

The EVSE appears to use a separate power supply of a bit over 12VDC. We might want to check that before connecting to 240V. We may have to provide our own separate 12V source.

Click to expand...

Are you surmising ... in the guts of the (simplified) emergency EVSE they assume 120V AC input, and use that to create 12VDC (and possibly 5VDC) to power the micro-controller ? Hmmm ... yes that could present a problem. (I was hoping for zero mods of the guts.) So, unless they design the US, Euro and Japanese versions input voltage tolerant and with PSU components that auto-adjust ...

Click to expand...

Something to verify before releasing the magic smoke.

Resurrecting this old tread because I could not fine a title that better matches my question:

What is the EVSE going to do if the car goes over the set current limit? For example the EVSE says 24A but the car keeps/jumps charging current to 32A. Does the J1772 standard include any required action on the EVSE part like gradually remove the pilot signal and then open the relays? Is there any overload allowed? For how long?

Thank you.

I don't have the standard handy, but I think it will just wait until the supply breaker trips.

Looking at Dousida on Amazon:

Control Box
Leakage protection(Restart recover)
Over-voltage under-voltage protection (self-checking recover)
Overload protection (self-checking recover)
Lightning protection

It seems that it has its own overload protection. I am not sure if is required by J1772 standard and how it works. I will look for the manual.

camasleaf said:

...
What is the EVSE going to do if the car goes over the set current limit? For example the EVSE says 24A but the car keeps/jumps charging current to 32A.

Click to expand...

For that to happen would require an error or fault on the car side. The OBC uses a current sense resistor for feedback and does closed-loop current control based on CAN buss commands from the VCM and the duty cycle of the PWM pilot signal from the EVSE.

The Panasonic and the Blink EVSE units also have current sensing internally, but i haven't studied other brands. No idea what the response would be if somehow an overcurrent occurred, but i would think it would drop the pilot and open the internal relays to stop the session.

What are you modifying to create such a condition?

I did not experience this condition. I am trying to see if the EVSEs performs a similar overload protection as a motor starter. If they do then electrical code could be updated where the breaker in the panel only provides short-circuit protection and thev overload (overtemp) protection is provided by the EVSE. I belive that in certain conditions this could reduce de wire/conduit size resulting in savings without compromising safety. For thousands and thousandsof installations this could add up.

Here is an example: 80A EV charging load that should never go over 80A since that is the limit of the chargers. Current code requirements dictate #3 line wires, #8 ground, 1" conduit with 100A breaker.

Since the load "never" goes over the 80A a #4 wire with the proper insulation material, that has an ampacity of 85A, should be sufficient if we look at the wire operation. Ampacity is defined as maximum continuous current at the specific temperature. So #4 will not even reach 75C regardless of how long the car is charging. But since the breaker does not like 75C at its terminals we cannot use an 80A breaker and need to use 125% breaker.

The 100A breaker will protect the #4 wire and the EVSE and the car charger from any short-circuit and ground-faults. But if the car decides to draw 100A then the 100A breaker will not trip and the #4 wire will overheat, destroy the insulation and cause a fire/fault.

If the EVSE will act as a motor overload set at 100% and additionally asked the car to reduce current if it reaches 80A then the EVSE is protecting the #4 wire from overheating or overloading.

If all EVSEs would be designed to act this way, for me this is a perfectly safe solution: #4 wire, 100A breaker, and 3/4" for a 80A EVSE.

Disclaimer: No, I do not plan to do this installation and I do not plan to burn the house down. This discussion is just theoretical since the EVSE behavior at 81A is not known nor standardized.

Any thoughts?

Can a higher ampacity be used if only 2 of the 3 wires is a current-carrying conductor?

a single #4 with the same insulation rating can carry 125 A in open air. How does that get de-rated for 2 current carriers in a conduit?

Can 3 #4 plus a #8 fit in the diameter of a 3/4" conduit?