LeftieBiker
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Re: Nissan EVSE not functioning

Sun Nov 21, 2021 11:50 pm

IIRC, Japanese grid voltage is around 100 volts. They need a flexible OBC.
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goldbrick
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Re: Nissan EVSE not functioning

Mon Nov 22, 2021 11:46 am

After some more thought, I think the issue may be the neutral line.

Most EVSE's don't use the neutral and can even be connected to 3-wire receptacles like a NEMA 6-50. The EVSE that comes with a Gen2 Leaf must use the neutral somehow since it can use the supplied converter plug to run on 120V which obviously needs the neutral line.

So....if the neutral was connected for 240V, the 2 hot phases would cancel and there would no neutral current (even though it was connected). On a 208V setup, the 2 phases are not balanced and the neutral current would be 1.73 times the current of either hot leg (if my math is right, not sure about that).

An EVSE that doesn't have a neutral connection wouldn't have this issue and the power would simply be reduced. The load is still unbalanced but that would only affect the windings in the source transformer, not the wiring to the receptacle (ie, there is no issue with excessive current in any wiring leg). In an apartment building, sub-division or industrial facility where 120V/208V wiring is often used, the thought must be that any imbalances in individual 208V circuits will balance out over the entire network. Also, the imbalance is only seen at the transformer which may have the means to handle this.

GerryAZ
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Re: Nissan EVSE not functioning

Mon Nov 22, 2021 7:44 pm

The neutral of a three-phase 208Y/120-volt system is solidly grounded the same as a single-phase 120/240-volt system. Most EVSE's test for a proper equipment grounding connection by passing a small current from line to ground so the output contactor will not close if the ground connection is not complete or the system neutral is not grounded. This is why a neutral ground reference is needed when charging with a portable generator. I believe the Nissan dual-voltage EVSE fails to charge on a 208-volt system because the voltage drops below its acceptable value for Level 2 charging when the current ramps up (it starts charging for a few seconds and then fails).

I have not tested the onboard charger in my 2019, but I tested the one in my 2011 and found that it would charge on Level 1 with voltage down near 100 at the input to the EVSE. I used a long light-duty extension cord to create a severe voltage drop under charging load to see what would happen and found that the car would charge down to the lowest level I was able to safely create. The light-duty cord would overheat if the car was allowed to charge for more than a few minutes.
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goldbrick
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Re: Nissan EVSE not functioning

Tue Nov 23, 2021 12:58 pm

What pins are connected through the 120V adapter provided with the Gen2 Leafs? I'm guessing it will use L1, N and G.

I agree that a 208V setup is very similar to a 240V split phase setup except that 2 hot legs aren't 180 degrees out of phase. With both 208V and 240V either L1 or L2 referenced to N gives 120V (RMS) and the only difference is when L1 is referenced to L2.

But with 240V, the v(t) of L1 is opposite of the v(t) of L2 so by Kirchhoff's law there is no neutral current. With 208V, the v(t) of L1 doesn't cancel the v(t) of L2 so there must be a neutral current that is bigger than either the L1 or L2 current, assuming the N was connected between L1 and L2 inside the power brick. I don't know if that's actually the case but since a simple adapter can change the 14-50 plug to a 120V plug it could be that the plug simply runs on L1-N for 120V and runs on L1-N-L2 when operating at 240V. This would result in zero neutral current on 240V since L1 = -L2 but with 208V the N current would be too large and the unit shuts down.

coulomb
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Re: Nissan EVSE not functioning

Wed Nov 24, 2021 7:53 am

goldbrick wrote:
Mon Nov 22, 2021 11:46 am
So....if the neutral was connected for 240V, the 2 hot phases would cancel and there would no neutral current (even though it was connected).
The On Board Charrger has only two AC input wires, and Jl772 only has two AC pins. So there is no way to connect two phases (hots) and a neutral.

208VAC doesn't have to be from a Y connected 3-phase system (with the centre point of the Y grounded). 208VAC can also result from the high leg delta connection (using L3 and N). I actually thought that this was the common way for a 3-phase transformer to be connected in the US. But perhaps it's only common in industrial settings.

As far as I know, the OBC doesn't care what voltage the two inputs have with respect to ground, as long as when a high impedance is connected to ground, a small current can be detected. In other words, the car will reject a floating supply, because then a GFCI won't work. I don't know if the car only checks one input or both for current to ground. [ Edit: one input is usually labelled L2/N, so I guess the car only tests for current from L1 to ground. ]

The image below (from the Wikipedia link) is practically a phasor diagram of the high leg delta, with each side of the triangle representing 240VAC. You can see that the distance from L3 to the centre tap is a little shorter than the sides of the triangle; a little trigonometry shows that it's sqrt(3)/2 (=0.866) shorter, and 0.866 x 240V = 207.8V.

Image

[ Edit 2: On further thought, if the transformer is connected as above with the high leg delta arrangement, then you have 240V readily available (using any two phases), so there is no reason to use 208V for an EVSE. ]
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goldbrick
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Re: Nissan EVSE not functioning

Thu Nov 25, 2021 12:04 pm

Thanks for chiming in. I agree that the OBC doesn't care about the phasing (or input voltage) of its inputs to ground or neutral since its not connected to neutral. Also, the OBC works at 208V (or 120V or 240V) when using other EVSEs, just not the Nissan supplied EVSE. So I think it's safe to say the issue with the EVSE not the OBC.

In the US, the EVSE is plugged into a NEMA 14-50 receptacle which has L1, L2, N and GND. As far as I can tell, 120/208 indicates 120V L1-N and L2-N phases which are 120 degrees out of phase with each other to yield 208V RMS across L1-L2.

My thought is that issue may be due to the supplied adapter which converts the 14-50 plug to a 5-15 plug. If the adapter connects the L1, N and GND of the 14-50 plug to the L1, N, GND terminals of the 5-15 plug, it seems to me that there must be a 'center tap' in the EVSE to make this work. If the adapter connects L1, L2, GND of the 14-50 plug to the L1, N, GND of the 5-15 plug, this wouldn't be necessary. But in the latter case, the adapter would connect L2 (on the 14-50 side) to N (on the 5-15 side) of the adapter. Maybe that's forbidden by UL or something?

jjeff
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Re: Nissan EVSE not functioning

Thu Nov 25, 2021 12:28 pm

The OBC only has 2 line inputs plus ground, in the case of 208/240v it sees 208/240v between its L1 and L2 input, in the case of 120v it sees 120v between its L1 and L2 inputs, the OBC only has 2 inputs plus ground. The OBC seems to function from around 100v to 265v, unfortunately not up to 277v which is a common commercial voltage for lighting and high-powered motors, last I knew Tesla did accept 277v but I'm not sure about the more recent models. If you want an EVSE that accepts a wide range of voltages get an aftermarket EVSE, the cheaper the EVSE the more apt it is to accept different voltages, it's really unforgivable the OEM Nissan dual voltage doesn't accept 208v which is an extremely common voltage in apartments and commercial settings.
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coulomb
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Re: Nissan EVSE not functioning

Fri Nov 26, 2021 3:23 pm

goldbrick wrote:
Thu Nov 25, 2021 12:04 pm
I agree that the OBC doesn't care about the phasing (or input voltage) of its inputs to ground or neutral since its not connected to neutral.

I should have been clearer: in the case of the high leg delta, one of the inputs to the EVSE and OBC is neutral. But that probably doesn't matter.
If the adapter connects the L1, N and GND of the 14-50 plug to the L1, N, GND terminals of the 5-15 plug, it seems to me that there must be a 'center tap' in the EVSE to make this work.
The only way I can think of that the Nissan supplied EVSE can work with 240 and 120V yet not 208V is if it uses a rare configuration where a transformer with two 120V primary coils is switched in series for 240V and in parallel for 120V operation. This transformer powers the electronics and the main relay of the EVSE. A smaller relay does the switching of the primary coils, based on the magnitude of the input voltage. So 208V might be too much for paralleled coils (hopefully some protection prevents overheating), or too low for the coils in series.

Actually, the primary coil might be center tapped, so the relay only needs to be single pole. But the principle is the same, just one coil versus two in the 120V configuration. This may be more like what you were thinking of.

Edit: I meant to add that the way that other EVSEs get around this is to use a high frequency switching power supply that can be designed to work with a wide variety of input voltages. These are smaller and often cheaper than a 60Hz iron transformer, so the latter are rare these days. But for some odd reason, Japanese designers seem to prefer the low frequency transformer approach.
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goldbrick
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Re: Nissan EVSE not functioning

Sat Nov 27, 2021 8:42 am

jjeff wrote:
Thu Nov 25, 2021 12:28 pm
it's really unforgivable the OEM Nissan dual voltage doesn't accept 208v which is an extremely common voltage in apartments and commercial settings.
I think that's a result of the adapter supplied with the Gen2 Leaf EVSE's. The EVSE can be used with at 240V or 120V with the adapter. Unfortunately it can't be used at 208V. In effect, the EVSE trades off the ability to run on 208V for the ability to run on 120V with a simple adapter.

Do any of the EVSE's that work at 208V work at 120V using the Nissan adapter? I'm not sure I'd even want to try it but it would be interesting to know if they worked or not.

On the Rav4Prime (and Prius Prime too I believe), the EVSE supplied in the US has a 5-15 plug for use on 120V. Apparently, the 'brick' part of the EVSE is the same as the one supplied in parts of the world where the power supply used is 200V (single phase to neutral). Some folks have built or bought adapters to plug their EVSE's 5-15 plug into a 14-50 receptacle. In effect, this connects the neutral on the 5-15 receptacle to the L2 on the 14-50 plug. I can't believe this is UL or NEC compliant and frankly I think it's dangerous.

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