# Confused About J1772 Pilot Signaling



## iruraz (Sep 4, 2012)

Hi all,

I am confused about J1772 pilot signaling between vehicle vmu and off-board charger. When vehicle is connected to off-board charger (any public charger-AC Level 2), charger needs to get vehicle battery informations to specify charging characteristic. How does it happen (I mean information sharing between vehicle and charger)? As far as I understand, they are sharing charging infos via PLC (power line communication). And for adjusting current they communicate via PWM (PWM duty cycle indicating ampere capacity).

I want to integrate J1772 inlet to my vehicle. There is board AVC2 (from modularevpower.com). Does this board communicate with BMS or vehicle vmu to adjust current capacity? And does this board transmit battery infos (which received from vmu or bms) to off-board charger? 

Best regards.


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## corbin (Apr 6, 2010)

Hi iruraz,
I’m confused by a few things you wrote. What is a vmu? 

Also, there isn’t an off board charger..the charger is still in your car with J1772. 

This wiki page explains it pretty well:

http://en.wikipedia.org/wiki/SAE_J1772

And with regards to adjusting current... who do you mean by “they”? The onboard car charger is supposed to look at the PWM signal and adjust the current it draws to be limited to what the J1772 charging station says it can provide. 

-corbin




iruraz said:


> Hi all,
> 
> I am confused about J1772 pilot signaling between vehicle vmu and off-board charger. When vehicle is connected to off-board charger (any public charger-AC Level 2), charger needs to get vehicle battery informations to specify charging characteristic. How does it happen (I mean information sharing between vehicle and charger)? As far as I understand, they are sharing charging infos via PLC (power line communication). And for adjusting current they communicate via PWM (PWM duty cycle indicating ampere capacity).
> 
> ...


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## corbin (Apr 6, 2010)

Also note:
http://www.corbinstreehouse.com/blog/2012/11/electric-bug-charger-control-design/

I implemented the J1772 myself. It doesn’t read the PWM because my charger is limited to 30amps, and all level 2 chargers (that I use) can do up to 30 amps. That...and there is no way to control the charging current pulled by the Manzanita charger (it is only controllable via a manual dial).

corbin


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## iruraz (Sep 4, 2012)

Hi Corbin,



> I’m confused by a few things you wrote. What is a vmu?


vmu = vehicle management unit



> Also, there isn’t an off board charger..the charger is still in your car with J1772.


Yes I have on-board charger (eltek 3kW). And I can charge my car from grid. Because it has small capacity. But my question is about public chargers.

I think I should ask the question new form:

I can integrate J1772 to my car. Should I connect J1772 inlet to battery directly or over my on-board charger? (My battery is about 330V and 90Ah.) After that, when I connect the J1772 level2 public charger to my car. What will happen? I mean, how does off-board charger (in this case it is public charger) understand current capacity? (In my opinion there should be communication between off-board charger and vehicle.)



> http://en.wikipedia.org/wiki/SAE_J1772


Yes it is useful but as I mentioned before I have not understand communication between off-board charger and vehicle

Regards.


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## dladd (Jun 1, 2011)

iruraz said:


> Hi all,
> 
> I am confused about J1772 pilot signaling between vehicle vmu and off-board charger. When vehicle is connected to off-board charger (any public charger-AC Level 2), charger needs to get vehicle battery informations to specify charging characteristic. How does it happen (I mean information sharing between vehicle and charger)? As far as I understand, they are sharing charging infos via PLC (power line communication). And for adjusting current they communicate via PWM (PWM duty cycle indicating ampere capacity).
> 
> ...


The charging station is not a charger, it's just the power supply. You supply your own charger, the J1772 is just the connector, and the pilot signaling just tells the charging station that you are plugged in and ready to accept power. It's really nothing different than a fancy plug. The charging station serves the same purpose that a Nema 15-50 outlet does, except for the safety of making sure there is no power present when plugging/unplugging the cord.


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## iruraz (Sep 4, 2012)

> The charging station is not a charger, it's just the power supply. You supply your own charger, the J1772 is just the connector, and the pilot signaling just tells the charging station that you are plugged in and ready to accept power. It's really nothing different than a fancy plug. The charging station serves the same purpose that a Nema 15-50 outlet does, except for the safety of making sure there is no power present when plugging/unplugging the cord.


@dladd, every charger is a power supply in the same time. If pilot signaling just tells the charging what is the meaning of PWM duty cycle?

http://en.wikipedia.org/wiki/SAE_J1772

in the link above it show the "PWM duty cycle indicating ampere capacity" table.

Regards.


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## onegreenev (May 18, 2012)

Private or public J1772 EVSE stations are not chargers. They are only smart outlets. Your car does the charging with the onboard charger.


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## dladd (Jun 1, 2011)

iruraz said:


> @dladd, every charger is a power supply in the same time. If pilot signaling just tells the charging what is the meaning of PWM duty cycle?
> 
> http://en.wikipedia.org/wiki/SAE_J1772
> 
> ...


power supply was not be the right way to say it, sorry. I like Pete's description of "smart outlet."


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## iruraz (Sep 4, 2012)

> Private or public J1772 EVSE stations are not chargers. They are only smart outlets. Your car does the charging with the onboard charger.


@onegreenev, @dladd thanks for your helps. 

In that case, maximal charging is as on-board charger capacity. But how can I adapt my car for quick charging? As far as I know there is only CHAdeMO standard for quick charger. Is there any solution for it?

By the way still I couldn't understand PWM duty meaning in pilot signaling (I am sorry for my ignorance)

Regards.


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## corbin (Apr 6, 2010)

iruraz said:


> Hi Corbin,
> 
> 
> 
> ...


I think you are confused..there is no such thing as a public charger. They are charging stations, which do little more than provide a 220v line and a relay that is turned on and off. Your car’s charger will still be used. Hopefully that helps clarify things! It drives me crazy when people call them “chargers” — they are not chargers, but just a station where you can charge your car using the car’s built in charger.

But also see the wiring diagram on my website for an example on how I incorporated the J1772 logic, and wired it to my BMS and charger. the Arduino turns the charger on and off depending on the J1772 proximity signal being latched/closed.

—corbin


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## corbin (Apr 6, 2010)

iruraz said:


> @onegreenev, @dladd thanks for your helps.
> 
> In that case, maximal charging is as on-board charger capacity. But how can I adapt my car for quick charging? As far as I know there is only CHAdeMO standard for quick charger. Is there any solution for it?
> 
> ...


Looks like the others replied before I hit submit.

Quick charging, using an external charger, is a different situation. I don’t know of any DIY people who have done it. You might be branching out on your own...definitely share any information you get on it.

Did you read the Wiki regarding the signal?

corbin


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## iruraz (Sep 4, 2012)

@corbin,



> It drives me crazy when people call them “chargers” — they are not chargers,


take it easy  you are right, it is not correct calling.



> But also see the wiring diagram on my website for an example on how I incorporated the J1772 logic, and wired it to my BMS and charger. the Arduino turns the charger on and off depending on the J1772 proximity signal being latched/closed.


Your website very helpful, thanks for it. (I have followed your website before this topic)



> Quick charging, using an external charger, is a different situation. I don’t know of any DIY people who have done it. You might be branching out on your own...definitely share any information you get on it.


I am seeking about quick charging. Of course, sharing is my philosophy 



> Did you read the Wiki regarding the signal?


I read, but I haven't understand. Maybe I should read it again in morning.

Regards.


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## corbin (Apr 6, 2010)

Oh yeah! I didn’t mean to indicate it was your fault for calling it a Charger...everyone does it..including people at my work who have electric cars. 

corbin



iruraz said:


> @corbin,
> 
> 
> 
> ...


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## onegreenev (May 18, 2012)

> Quick charging, using an external charger, is a different situation. I don’t know of any DIY people who have done it. You might be branching out on your own...definitely share any information you get on it.


Corbin, aside from an external charger I have done fast charging but only to 150 amps input current for a short time and 75 input amps for a complete charge using an external DC source of power from a bank of solar batteries and running through an inductor and my controller. Charging is configured with the controller and it does CC/CV. I will have it connected up again soon for more videos. I did one video on this. Works great. Get some cooling to the inductor and you can if your source can handle the current go up to 250 input amperage current. For 100ah cells that is only 2.5C. Not an easy thing to do. 

Pete


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## iruraz (Sep 4, 2012)

> The charging station can use the wave signal to describe the maximum current that is available from the charging station with the help of pulse width modulation: a 16% PWM is a 10 A maximum, a 25% PWM is a 16 A maximum, a 50% PWM is a 32 A maximum and a 90% PWM flags a fast charge option.


http://en.wikipedia.org/wiki/SAE_J1772

Quote is from Wiki. 

When vehicle charges, does vehicle send command to charging station via PWM duty cycle? (I mean current should decrease after a while according to charging rule of ConstantCurrent-ConstantVoltage) Or is it for only to inform vehicle about charging amperage capacity? How does J1772 EVSE understand charging current value when vehicle is plugin? 

Regards.


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## dougingraham (Jul 26, 2011)

iruraz said:


> When vehicle charges, does vehicle send command to charging station via PWM duty cycle? (I mean current should decrease after a while according to charging rule of ConstantCurrent-ConstantVoltage) Or is it for only to inform vehicle about charging amperage capacity? How does J1772 EVSE understand charging current value when vehicle is plugin?


When plugged into the car the EVSE tells the charger in the vehicle how many amps it is allowed to draw. The only thing the charger in the car tells the EVSE is that it is ok to turn on the power.

The J1772 when operating looks for a ground fault, an over current condition, and the continuing presence of the connection to the charger electronics.

And when charging the current slowly increases as the pack voltage increases when in the constant current portion of the charge and only when the charger switches to constant voltage mode does the current decrease.


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## corbin (Apr 6, 2010)

onegreenev said:


> Corbin, aside from an external charger I have done fast charging but only to 150 amps input current for a short time and 75 input amps for a complete charge using an external DC source of power from a bank of solar batteries and running through an inductor and my controller. Charging is configured with the controller and it does CC/CV. I will have it connected up again soon for more videos. I did one video on this. Works great. Get some cooling to the inductor and you can if your source can handle the current go up to 250 input amperage current. For 100ah cells that is only 2.5C. Not an easy thing to do.
> 
> Pete


that’s awesome pete! 

I would be interested to know if any DIY people implemented/figured out the CHAdeMO protocol for the standardized DC fast charging.

corbin


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## onegreenev (May 18, 2012)

corbin said:


> that’s awesome pete!
> 
> I would be interested to know if any DIY people implemented/figured out the CHAdeMO protocol for the standardized DC fast charging.
> 
> corbin


Thanks, I would however love a hot CHAdeMO charger for home. Would give me more opportunities to travel further in a day. With the fast charging for my VW I am hoping to get some good use from my fun little roadster this summer.


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## iruraz (Sep 4, 2012)

> When plugged into the car the EVSE tells the charger in the vehicle how many amps it is allowed to draw. The only thing the charger in the car tells the EVSE is that it is ok to turn on the power


@dougingraham, does EVSE ask for every value via pwm duty? Because there are different values which changes according to duty you can see below.



> Duty Cycle	Max Current
> ----------- -----------
> < 3% Error
> 3% - 7% Digitial Com Required
> ...





> Corbin, aside from an external charger I have done fast charging but only to 150 amps input current for a short time and 75 input amps for a complete charge using an external DC source of power from a bank of solar batteries and running through an inductor and my controller. Charging is configured with the controller and it does CC/CV. I will have it connected up again soon for more videos. I did one video on this. Works great. Get some cooling to the inductor and you can if your source can handle the current go up to 250 input amperage current. For 100ah cells that is only 2.5C. Not an easy thing to do.


@onegreenev, I will follow your news about CHAdeMO 

Regards.


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## onegreenev (May 18, 2012)

No, not CHAdeMO. I'd like to do CHAdeMO. What I am doing is the fast charge through my Synkromotive. Both AC or DC. With a high voltage pack I can use AC or with a lower voltage pack I can charge off stationary DC. I have a large Solar Battery Bank for using on a small 120 volt pack. 

But I am watching CHAdeMO very closely. When I can go that direction I surely will as I do drive my Leaf enough to warrant having one. Even at half what a CHAdeMO can do would make me a happy camper at this time. 

Pete


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## iruraz (Sep 4, 2012)

onegreenev said:


> No, not CHAdeMO. I'd like to do CHAdeMO. What I am doing is the fast charge through my Synkromotive. Both AC or DC. With a high voltage pack I can use AC or with a lower voltage pack I can charge off stationary DC. I have a large Solar Battery Bank for using on a small 120 volt pack.



@Pete, how do you control charging process?


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## onegreenev (May 18, 2012)

iruraz said:


> @Pete, how do you control charging process?


The controller does that.


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## iruraz (Sep 4, 2012)

onegreenev said:


> The controller does that.


Thanks. It is ok.

Regards.


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## hbthink (Dec 21, 2010)

L3 charging is offboard DC charging usually 25kW to 50kW rate or 30-100 amps at up to 400v dc. The process is controlled in Chademo via a 500kb CAN interface. In the SAE standard the PLC provides communications control of charging across the PILOT signal and ground, using PLC (homeplug, greenplug basically an OFDM across the pilot). Both fast charge standard require quite a bit of safety checking before process begins and the chargers need to be able to be both current controlled during charging but also voltage controlled during the initial testing phase. I have done software for both systems and would consider an open source project for both chargers. Right now I'm on vacation so maybe I'll do this when I get back.

SAE DC fast charging is unique in that the plug is a combo and can allow L1, L2 (AC or DC), and L3 charge rates. Mode control is moderated by the voltage switching used in J1772 plus the addition of PLC communications. Chademo uses a separate plug.

On the left is the worlds first 83 Rabbit with SAE Fast charge interface.

Steve


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## iruraz (Sep 4, 2012)

> I have done software for both systems and would consider an open source project for both chargers. Right now I'm on vacation so maybe I'll do this when I get back.


@hbthink, is there any website or documents which include your works?

Regards.


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## ElectriCar (Jun 15, 2008)

OK I've been using these free charging stations made by Eaton in my area but all that I've found won't charge my truck but for a short time, tripping out on over current. Reason being they are all L216 models on a 30A breaker, max output is rated 3.8KW, somewhere around 23A. My Zivan charger is an NG5 rated at 5KW. Eaton makes an L230 which is a 7.2KW charger but we don't have any that I've seen in my area.

AFAIK, the Zivan isn't capable of any communication like that unless we can mod it somehow or they've come up with a mod at Zivan. What I have to do now is turn down the current pot until I get it to about 23 amps and it'll charge fine then. If I leave it there man it takes forever to charge it seems. It could be done with a toggle switch and two resistor values to take the place of the OEM trim pot. I just don't want to do that!


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