maini
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Re: Cheap L2 EVSE by converting the 2013-14 Nissan L1 EVSE -

Sat Sep 06, 2014 10:37 pm

feathersjr wrote:I just bought a 2015 Leaf, and decided to do this mod on my trickle charger. I intend to use it as a 240V charger only, since I picked up an extra 12 Amp 120V charger from a Fiat owner.
The chaps at Nissan decided to put Tamper Proof screws underneath the plastic tabs, kind of a Torque head with a pin in the middle. Had to drill them out, just a PIA. I measured the resistance of the Thermister (the 2 yellow wires) and a room temperature it was about 17.1 K Ohms. No where near the 33 K Ohms that I've seen posted. I placed the plug in the sun and watched the resistance start to drop down which is what a termistor will do. So I am puzzled about the value of the resistance I am reading. Perhaps the latest EVSE has been modified somewhat? I will continue and find a resistor from a box of stuff I have laying around and see if it works out OK.
Be kind, this is my first post ;)


The 33K Ohm resistor has worked fine for the last 3 months now. Please remember the 33K Ohm resistor was put in place of FCDC device at the point where a plug with 2 yellow wires plug in. It works fine I use this at least 3-4 times a week and leave it ON overnight. Normal behavior and fast L2 charging at 12Amps.. no errors or any other messages. Build with Confidence :)

Also for the tamper proof torx screws.. I managed to open them easily with a regular torx driver, I think it latches on even with the pin in the middle.
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turbo2ltr
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Re: Cheap L2 EVSE by converting the 2013-14 Nissan L1 EVSE -

Sun Sep 07, 2014 10:17 am

Just because it works, doesn't mean it's right. Not saying it's wrong, but engineering isn't about "if it works", it's about "is it designed properly". Unless you have done a complete analysis of the circuit and it's components, you can't be sure you aren't pushing a part past it's limit and won't start a fire sometime down the road.

If the two yellow wires go to a thermister in the OEM plug (I have no idea if they do, I have no experience with it and just going by what the previous poster said), then it's there to monitor temperature of the plug. I would assume that if the temperature got too high (too low of a resistance) then the EVSE will stop charging. It's a safety feature that has been bypassed with the addition of a 33k ohm resistor that tricks the EVSE into thinking the plug is very cold. Obviously there is some code in the EVSE that checks to make sure the thermistor is within a certain range. Taking it away would put the resistance outside of the acceptable range and throw a fault.

I am curious though where the term "Frequency Dependent Charging Device"/FDCD came from and why, if there is a thermister connected to the two yellow wires, are they labeled so. Searching google, it seems to be a term that was made up by whoever did the instructable and perpetuated by the OP.
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srl99
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Re: Cheap L2 EVSE by converting the 2013-14 Nissan L1 EVSE -

Sun Sep 07, 2014 10:35 am

A full service hardware store should have the proper driver (bit) for that "security" screw, and more screws if you need them.

maini
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Re: Cheap L2 EVSE by converting the 2013-14 Nissan L1 EVSE -

Sun Sep 07, 2014 7:46 pm

turbo2ltr wrote:Just because it works, doesn't mean it's right. Not saying it's wrong, but engineering isn't about "if it works", it's about "is it designed properly". Unless you have done a complete analysis of the circuit and it's components, you can't be sure you aren't pushing a part past it's limit and won't start a fire sometime down the road.

If the two yellow wires go to a thermister in the OEM plug (I have no idea if they do, I have no experience with it and just going by what the previous poster said), then it's there to monitor temperature of the plug. I would assume that if the temperature got too high (too low of a resistance) then the EVSE will stop charging. It's a safety feature that has been bypassed with the addition of a 33k ohm resistor that tricks the EVSE into thinking the plug is very cold. Obviously there is some code in the EVSE that checks to make sure the thermistor is within a certain range. Taking it away would put the resistance outside of the acceptable range and throw a fault.

I am curious though where the term "Frequency Dependent Charging Device"/FDCD came from and why, if there is a thermister connected to the two yellow wires, are they labeled so. Searching google, it seems to be a term that was made up by whoever did the instructable and perpetuated by the OP.



OK.. I am a EE Engineer and did all the research before I made this change ...the job of the FDCD is to figure out if the plug has heated up due to changes in the frequency drop due to overload of the Grid. All us Engineers know that if the Frequency drops then the power factor reduces hence the plug will begin to heat up. Both The Open EVSE and the modified EVSE from EVSEupgrade do not use this facility and even in the specifications this is not mentioned... so there is no Harm in making this change.

As for pushing the components.. I have checked it out already... the original LIVE (120V) and the Neutral (0V) go through two relays both are capable of handling 250V and 30A each. ALL I am doing is sending two different phases of 120V each to the car. The original EVSE was sending 120V and Neutral and I am sending 120V and 120V (two different phases of course). So the wire which in the original device was carrying Neutral is now carrying 120V of another phase.

So before you start making guesses about how this solution was worked or put together and tested please do research better or have some concrete examples of failures or possible failure scenarios backed with some electrical engineering theory.
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turbo2ltr
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Re: Cheap L2 EVSE by converting the 2013-14 Nissan L1 EVSE -

Mon Sep 08, 2014 4:34 am

Did you read the PDF posted in the instructable? ( I did not see it prior to my first post)

A "Frequency Dependent Charging Device" reads the frequency of the grid, not temperature of the plug, to adjust power to the charger. That PDF was a whitepaper from a researcher and there is no indication (other than a claim in the instructable) that this EVSE supports grid-frequency-based current control. The word "temperature" isn't even mentioned in the PDF. Relying on the resistance of the plug's connection to detect a temperature change due to increased current due to a decreased power factor due to a fluctuation of the frequency is an incredibly inefficient method of frequency detection and no engineer in their right mind would design something like that.

Bottom line, the thermistor is a simple safety device to decrease the chance of a fire due to a bad wall socket and it has nothing to do with "FDCD". And it has been bypassed by the use of the 33k ohm resistor. In the end, it probably won't matter if it's there or bypassed assuming people aren't plugging it into an ancient socket, but people should understand what they are bypassing and let them make their own decision if it's something they are willing to risk. I'm sure you don't want to be responsible for telling someone to bypass a safety device and have something bad happen.

That's great the relay can handle the voltage. But where does the control circuit get it's power from and what happens when it sees 220 on the input instead of 110?

You should read some of my earlier posts on this board and not assume the level of knowledge I have.
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maini
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Re: Cheap L2 EVSE by converting the 2013-14 Nissan L1 EVSE -

Mon Sep 08, 2014 8:22 am

I never said there was a thermistor in there... I think you mentioned that.

The control circuit still works on 110V. Please read the modification carefully and with your esteemed knowledge you should be able to understand this modification and recognize that already.

I know of at least 10-15 people who have done this modification and it is working fine for over 300 plus charges... around 100 for me. If that is not proof enough for you.

Why do all the other third party EVSE manufacturers not using the FDCD in their designs?? I know Fiat does not have it either?? Please enlighten us..
Last edited by maini on Thu Oct 16, 2014 2:37 pm, edited 1 time in total.
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Re: Cheap L2 EVSE by converting the 2013-14 Nissan L1 EVSE -

Wed Oct 08, 2014 3:12 pm

if the thingy in the plug reacts to temperature my guess (NOT an EE) would be thsi is strictly for 120v charging.

ie at 12 amps your PUSHING the limits of typical household outlets to near their max rated power. this is a safety device so if the plug gets hot it turns off? so if you plug it into an underrated outlet or faulty outlet and things "heat up" it will turn off the charger ??

I imagine this would not be required on dedicated rated 240v outlets designed with a buffer to handle this kind of power.

just my guess.

I have 2 and maybe soon a third trickle charger so I may try this mod.
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nedfunnell
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Re: Cheap L2 EVSE by converting the 2013-14 Nissan L1 EVSE -

Wed Oct 08, 2014 5:18 pm

I am also an engineer, so I feel qualified to add my voice to the technical discussion.

A few things to point out:
[*]This modification, if performed as specified, does not apply 240v power to any component not rated for it.
[*]The extra 120v is flowing through a separate, fully insulated conductor.
[*]The loss of the FDCD/thermistor is real, but the risk can be fully mitigated by the use of properly rated connectors. More on this below.
[*]No additional current is flowing than in the original design- 12 amps both ways. Therefore, no more heat can be produced.
[*]This modification is intended to be carried out by technically savvy persons, able to assess the inherent risk of doing so.

On the FDCD/thermistor: I believe this is indeed a thermistor. Measuring the heat of the connector is a bright idea on EVSEs which operate at(not beyond) the limit of the design and code. Especially true with flaky, old, or corroded outlets out there. I've warmed up some connectors pretty hot myself. However, please consider this- this modification replaces the original connector, rated for 15A, with a new one rated for 30A. This instantly mitigates any risk of operating without temperature feedback, because the connector is no longer being operated anywhere near its limit- half, in fact. Furthermore, many other EVSE designers saw fit to leave a temperature measurement device out entirely, even with a plug being used at its limit. Based on these facts, I see no risk at all in bypassing the FDCD/thermistor when a higher-capacity connector is used. Notably, if you were going to use a 15A connector, you'd just going to be leaving the original, FDCD/thermistor-equipped one on there- so it's a wash anyway. Even if operated with a 15A connector without a temperature measurement device, the risk is no more than Fiat owners take every day with their non-protected EVSE plugs.

On the heat question: This modification works because of two equations: P=V*I, or power is voltage multiplied by current. The EVSE tells the car to draw the same current before and after the mod. So previously, 120v*12A=1440W of charging power available. After the modification, it becomes 240*12A=2880W, so double. The power flowing through the wire is double, but the power dissipated as heat in the wire does not double. Why? That is the second equation for finding power: P=I^2*R, or power is resistance times current squared. Voltage isn't in that equation at all- I could run 12A through a wire a 12V, 120V, or 1200v and the wire would heat up the same amount. The resistance of the wire remains constant unless it is damaged in some way.

Regarding "pushing" outlets near their max power- a standard NEMA 5-15 outlet is rated for 15A. EVSEs draw only 12A because the National Electric Code states that plugs, connectors, and receptacles should be used at their maximum power only intermittently, not constantly. When in constant use, the maximum allowed is 80% of the nominal maximum, or 12A in the case of a 15A outlet. 12A is already a reduced rate for safety, and if the connector is in serviceable condition it will do fine with a 12A constant load. If it is faulty, there is a real risk, but that goes for any piece of equipment. Don't plug your EV into suspect outlets.

Bottom line: I believe that this modification is safe when carried out by qualified persons. You know who you are. If in doubt, spend the dough on EVSEupgrade.
Last edited by nedfunnell on Wed Oct 08, 2014 5:25 pm, edited 1 time in total.

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Re: Cheap L2 EVSE by converting the 2013-14 Nissan L1 EVSE -

Wed Oct 08, 2014 5:23 pm

I am going to add some fine print to my last post:
I used the DC formula for power which are derived from Ohm's law, V=IR. The different P= formulae are different methods for getting P when you have different information, like I and V but not R, R and I but not V, etc. Technically, AC volts times AC amps results in VA, not watts because AC loads can have a power factor which throws things off. However, in this instance, because the Leaf's charger is power-factor corrected (above 0.96 from my research), this makes almost no difference. Critical armchair engineers and safety nazis, you have been disclaimed.

maini
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Re: Cheap L2 EVSE by converting the 2013-14 Nissan L1 EVSE -

Thu Oct 16, 2014 2:34 pm

nedfunnell wrote:I am also an engineer, so I feel qualified to add my voice to the technical discussion.

A few things to point out:
[*]This modification, if performed as specified, does not apply 240v power to any component not rated for it.
[*]The extra 120v is flowing through a separate, fully insulated conductor.
[*]The loss of the FDCD/thermistor is real, but the risk can be fully mitigated by the use of properly rated connectors. More on this below.
[*]No additional current is flowing than in the original design- 12 amps both ways. Therefore, no more heat can be produced.
[*]This modification is intended to be carried out by technically savvy persons, able to assess the inherent risk of doing so.

On the FDCD/thermistor: I believe this is indeed a thermistor. Measuring the heat of the connector is a bright idea on EVSEs which operate at(not beyond) the limit of the design and code. Especially true with flaky, old, or corroded outlets out there. I've warmed up some connectors pretty hot myself. However, please consider this- this modification replaces the original connector, rated for 15A, with a new one rated for 30A. This instantly mitigates any risk of operating without temperature feedback, because the connector is no longer being operated anywhere near its limit- half, in fact. Furthermore, many other EVSE designers saw fit to leave a temperature measurement device out entirely, even with a plug being used at its limit. Based on these facts, I see no risk at all in bypassing the FDCD/thermistor when a higher-capacity connector is used. Notably, if you were going to use a 15A connector, you'd just going to be leaving the original, FDCD/thermistor-equipped one on there- so it's a wash anyway. Even if operated with a 15A connector without a temperature measurement device, the risk is no more than Fiat owners take every day with their non-protected EVSE plugs.

On the heat question: This modification works because of two equations: P=V*I, or power is voltage multiplied by current. The EVSE tells the car to draw the same current before and after the mod. So previously, 120v*12A=1440W of charging power available. After the modification, it becomes 240*12A=2880W, so double. The power flowing through the wire is double, but the power dissipated as heat in the wire does not double. Why? That is the second equation for finding power: P=I^2*R, or power is resistance times current squared. Voltage isn't in that equation at all- I could run 12A through a wire a 12V, 120V, or 1200v and the wire would heat up the same amount. The resistance of the wire remains constant unless it is damaged in some way.

Regarding "pushing" outlets near their max power- a standard NEMA 5-15 outlet is rated for 15A. EVSEs draw only 12A because the National Electric Code states that plugs, connectors, and receptacles should be used at their maximum power only intermittently, not constantly. When in constant use, the maximum allowed is 80% of the nominal maximum, or 12A in the case of a 15A outlet. 12A is already a reduced rate for safety, and if the connector is in serviceable condition it will do fine with a 12A constant load. If it is faulty, there is a real risk, but that goes for any piece of equipment. Don't plug your EV into suspect outlets.

Bottom line: I believe that this modification is safe when carried out by qualified persons. You know who you are. If in doubt, spend the dough on EVSEupgrade.


THANK YOU Nedfunnel.. very well put.. although I am an EEE by education and know the stuff but I am sure no one could have articulated this any better. YES have been safety using this mod for the last 4-5 months with over 3800 miles on the car and over 100-200 charges between my car and my friends for whom I have done this mod successfully!!

Cheers!!
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