Charging the Leaf using a step-down transformer

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user 24513

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Hi all- I am sure this is covered somewhere herein, but I can not find it and am hoping that you will take pity on me. I have been charging L1 at my garage, a long way from the house, it has worked fine for a couple of years but the voltage while charging (at the garage ) is about 100 volts and I know this is terrible for efficiency and speed. So today I dragged out an old 240V-120V transformer, swapped out the breakers at the house, ran 240 to the garage and plugged the Nissan factory EVSE in. Voltage reads 120 exactly, herz is 60 exactly, but the EVSE just blinks and does not power up. Plugging it back into a regular 120V outlet it all works fine. Some sort of workaround is needed clearly..... Similar to charging with a generator? Thanks all,... Dan
 
Ground is good, I have tried adding a separate ground along the way and the EVSE still blinks green, never starts charging OR shows Fault.... and the EVSE still works on the other older smaller circuit..... Something about transformed AC and the ground being separate? do I need to ground the body of the transformer? will try that.....
 
Even with that ground all the way back uninterrupted, the Nissan EVSE would not work. (although the Duosida does).... the transformer is ancient and I have a newer one with a grounding wire attached, which MAY solve the issue..... But thanks Leftie for your thoughts I will keep plugging away!
 
The OEM EVVSE has an internal circuit which does a ground check before it will turn ON. It intentionally shorts out the input leads to ground to measure a current and verify that a path to safety ground exists.

Ground in your Mains panel is the mid-point of the transformer secondary on the pole at the street and the metal rod driven into the earth, which is also connected to the Neutral of the Line-Neutral pair of wires that provides 120vac. So both the 120 Line-Neutral and the 240 Line-Line have a path back to the earth thru the green ground wire in the connector plug.

But your step-down transformer is an isolation transformer--the secondary is totally isolated from the primary. So neither leg of your secondary has any connection path to ground or protective earth even if you run a wire from the panel or right at the transformer. So the ground test fails in the EVVSE and it won't turn ON.

You would need to connect the "Neutral" (wide blade of the 120vac plug, white wire) side of your isolated secondary to the green ground wire in order to pass the check.

This same issue can occur when trying to use a portable generator to supply AC for the EVVSE--unless the Neutral is tied to Ground it will fail the internal check.
 
nlspace said:
You would need to connect the "Neutral" (wide blade of the 120vac plug, white wire) side of your isolated secondary to the green ground wire in order to pass the check.
Agree but not sure if it's safer but don't some people use a plug with a resistor(not sure of value but for sure in K-ohms) to bond the neutral to ground? I believe this fools the check but still has some degree of isolation between ground and neutral.....
 
nlspace said:
The OEM EVVSE has an internal circuit which does a ground check before it will turn ON. It intentionally shorts out the input leads to ground to measure a current and verify that a path to safety ground exists.

Ground in your Mains panel is the mid-point of the transformer secondary on the pole at the street and the metal rod driven into the earth, which is also connected to the Neutral of the Line-Neutral pair of wires that provides 120vac. So both the 120 Line-Neutral and the 240 Line-Line have a path back to the earth thru the green ground wire in the connector plug.

But your step-down transformer is an isolation transformer--the secondary is totally isolated from the primary. So neither leg of your secondary has any connection path to ground or protective earth even if you run a wire from the panel or right at the transformer. So the ground test fails in the EVVSE and it won't turn ON.

You would need to connect the "Neutral" (wide blade of the 120vac plug, white wire) side of your isolated secondary to the green ground wire in order to pass the check.

This same issue can occur when trying to use a portable generator to supply AC for the EVVSE--unless the Neutral is tied to Ground it will fail the internal check.

Thanks, it makes sense explained that way- Duosida must not have the ground check circuit.....
 
A 20V drop is quite a lot and even at 240V it will still be a 10V drop. I'd try to charge closer to the panel or run a new supply line to the garage. Easy for me to say of course....
 
If you now have a 240 volt AC circuit near by where you park, why are you trying to still charge on 120 volts? Are both your EVSE's only 120 volt?

If so you can easily convert your OEM Nissan EVSE to 240 volt 12amp. This is what I did to mine as soon as I got it home, in fact the first at home charge I did was after I converted my OEM EVSE to 240 volts. If you are comfortable running new electrical circuits (like I am) then you 100% have the skills to do this mod.

Not the best video but pictures are worth more than words (good pictures are):
https://www.youtube.com/watch?v=QIvfiajGrR0

Now I didn't do the plug hack he did. For me it was cleaner and simpler to just put on a spare dryer cord (14-30) I already had collecting dust from a dryer long gone.

Mine more closely followed post when I did mine but I used a 22KOhm 1/4watt resistor for the plugs temp sensor (yellow wires) :
https://www.mynissanleaf.com/viewtopic.php?f=26&t=16948

In my electronics bin I found a matching 2-pin plug that the temp sensor wires from the original plug end uses, so my original plug end is uncut and could be put back together if needed (thrown in my electronics bin for now).

Per LeafSpy I get a solid 2,600+ watts into the battery pack now with no other active battery draws.
 
My goal had been to charge as slowly as possible, since we rarely need much charging that can not be accomplished overnite at the lowest rate (12A 120V), using a little mechanical crank timer to get to the percentage charge we want to see (in the range of 60% plus or minus). But to try to eliminate all the line loss from this draw (about 20 V), I was trying various transformers but they draw AT LEAST .7 Amps at 240V when not in use, so.....what I have set up now is 240V NOT transformed, 15 A Duosida, which shows a voltage drop of about 20V also but this is a smaller proportion of 240V so should be more efficient. We are now experimenting with how not to overcharge- using the Leaf built-in timer we will be able to figure out, charging off-peak middle of the nite, how not to overcharge, and the Plus has that cool little button which says Charge Now which overrides the timer if we ever need to catch up.... anyway, that is the current set-up and the transformers were a rabbit hole.
 
I've been using L1 charging lately too and it does make predicting the final charge much easier. Another nice about the 30kWh battery, like the 1 mile per %SOC thing. When I'm down to about 20-25% I just plug it in at night and the next morning it's at 70-80% SOC. Easy peasy.
 
I see... It took me a few days at a set charge level (L2 240volt 12amp) playing with the Leaf's (30kWh) charging departure timer to figure out the sweet spot (80% SOC). I typically leave at 7:30am on work days and so I found for me the sweet spot was setting the charge timer for a departure time of 10:50am.

Setting the depart timer for 10:50am my SOC is always around 80% come 7:30am no matter what the previous days ending SOC was. I don't sleep in on non-work or work from home days (4 kids) so it's never an issue for me to walk outside at 7:30 to unplug.

It's interesting that you are seeing a 20v drop with your 240v circuit at 15 amps. Didn't you say you just recently installed this circuit? What size wiring did you use and how far is the run?

*Wiring Police look away now*
Admittedly I'm only 25ft away from the breaker panel in my shop, but I ran 10AWG (10-4) wire in 1inch MC (metal clad) flex conduit (so lots of room\air) for my L2 27.5 amp EVSE. It's adjustable and has a voltage readout. With no load the line voltage is 242v, under a load of 27.5 amps it only drops 2 volts to 240v. I've verified the readings with a meter at the outlets output.
 
1byte said:
It's interesting that you are seeing a 20v drop with your 240v circuit at 15 amps. Didn't you say you just recently installed this circuit? What size wiring did you use and how far is the run?

*Wiring Police look away now*
Admittedly I'm only 25ft away from the breaker panel in my shop, but I ran 10AWG (10-4) wire in 1inch MC (metal clad) flex conduit (so lots of room\air) for my L2 27.5 amp EVSE. It's adjustable and has a voltage readout. With no load the line voltage is 242v, under a load of 27.5 amps it only drops 2 volts to 240v. I've verified the readings with a meter at the outlets output.

Yup you got it right, the wire is way undersized since we never anticipated charging an electric vehicle in the garage, probably 300 feet from the house..... so trying now to find a 240V EVSE that charges at the lowest rate to minimize the line loss. First world problems but glad to have them.....
 
I'm not an electrician but at 300' I think there are separate calculations required by most codes to size wires to prevent voltage loss.

That's quite a run and quite a voltage drop. I assume the line is direct buried?
 
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