# Public Charge Stations (J1772, etc)



## major (Apr 4, 2008)

cts_casemod said:


> Hi Folks
> 
> Can someone please describe what i need to do in order to get power from an EV public charge station (EVSE)?
> 
> ...


Type J1772 into the search field and find numerous threads; many on the subject like this one: http://www.diyelectriccar.com/forums/showthread.php?t=81412&highlight=J1772 There are also vendors who will sell you the parts needed and instructions. Check with those who advertise on this board.


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## cts_casemod (Aug 23, 2012)

major said:


> Type J1772 into the search field and find numerous threads; many on the subject like this one: http://www.diyelectriccar.com/forums/showthread.php?t=81412&highlight=J1772 There are also vendors who will sell you the parts needed and instructions. Check with those who advertise on this board.


Hi Major,

I did have a look before, but haven't found anything relevant to my query.
I have all the hardware set up but when I plug into the EVSE there is no output since I need to communicate with it. I was looking for the relevant information on how to trigger the EVSE to supply the charger, hopefully with some delay timer or a switch to Start/Stop the charge.

Surely most DIY EV drivers charge at home and hence use domestic plugs, hence I am finding it hard to find what I need.

Regards


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## major (Apr 4, 2008)

http://rebirthauto.com/shop/charging/j1772-vehicle-control-board-avc2/

http://www.aprs.org/charging-DIY.html 

http://www.electriccarpartscompany....to-Door-from-China-br-0-39ft-0-12m_p_384.html 

http://blog.evtv.me/2011/07/build-your-own-j1772-charge-station-the-electric-porsche-914/ 

Not too difficult to find.


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## dougingraham (Jul 26, 2011)

cts_casemod said:


> I have two charge modes available 8A and 16Amp. But I have no idea how to tell the EVSE my vehicle can charge at x amps.


It doesn't work that way. The EVSE tells the car how much power it is allowed to pull. When ready the car tells the EVSE it is ok to turn on the power. There are devices available that can go between the EVSE and the charger to get them to turn on.

Here is one example available on EBAY.

Link to AVC2


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## cts_casemod (Aug 23, 2012)

dougingraham said:


> It doesn't work that way. The EVSE tells the car how much power it is allowed to pull. When ready the car tells the EVSE it is ok to turn on the power. There are devices available that can go between the EVSE and the charger to get them to turn on.
> 
> Here is one example available on EBAY.
> 
> Link to AVC2



What I am looking for, so far without success is some circuit (car side) that can read the EVSE capability and adjust the charger as such.

Say I only have 10Amps available. How do I tell my charger to throttle back from 16 to 8? Most devices such as the one you described only turn the supply on, the charger is not told how much to pull.

Regards


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## major (Apr 4, 2008)

cts_casemod said:


> What I am looking for, so far without success is some circuit (car side) that can read the EVSE capability and adjust the charger as such.
> 
> Say I only have 10Amps available. How do I tell my charger to throttle back from 16 to 8? Most devices such as the one you described only turn the supply on, the charger is not told how much to pull.


O.K. You need to detect the PWM level on the pilot. 


> 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.


 More detail here: http://en.wikipedia.org/wiki/SAE_J1772 Is that what you're after?


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## dougingraham (Jul 26, 2011)

cts_casemod said:


> What I am looking for, so far without success is some circuit (car side) that can read the EVSE capability and adjust the charger as such.


The best place for this is built into the charger. A general purpose device can't exist to do this because it can't know how to control the charger.



cts_casemod said:


> Say I only have 10Amps available. How do I tell my charger to throttle back from 16 to 8? Most devices such as the one you described only turn the supply on, the charger is not told how much to pull.


I think you are worried about something that will not be a problem for you. Since you don't have a high power charger you can just set the charger you have to operate at 16 amps and you will be ok 99.9% of the time. Most of the L2 EVSE's out there can do 30 amps.

30 amps and 240 volts is 7.2kw and is the capability of most of the EVSE's. Your charger can probably do 16amps at 240 volts so it is a 3.8kw charger. The EVSE's don't care how much you pull as long as it is under their limit. An EVSE is just a contactor that closes when the charger tells it to and a GFI (Ground Fault Interrupter) to try to protect you from wiring issues (or touching things that should not be touched). There will be a circuit breaker feeding the EVSE and if it is smart enough it could also monitor the current and open up if you try to pull too much.


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## cts_casemod (Aug 23, 2012)

major said:


> O.K. You need to detect the PWM level on the pilot.
> More detail here: http://en.wikipedia.org/wiki/SAE_J1772 Is that what you're after?


Hi Major, Ill explain:

When connecting to an EVSE I have a PWM signal indicating the power limits as per the above protocol. Systems as the above mentioned AVC2 module linked above enable the EVSE output, but once this is done my chargers will draw a full power of 19Amps (2x8Amp for main and up to 3 for the accessory battery charger). 

I don't have that much power available at home nor in level 1 stations, where I will be using the open EVSE programmed with a 10-13Amps limit depending on the cable length.

I need to convert the EVSE pilot signal to a reference for my main charger, so that power can be throttled as required without user input, keeping the current draw within the limits of the available supply. This is what I am having trouble finding. 

Maybe I am the first attempting such a thing on a converted EV?

Regards


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## cts_casemod (Aug 23, 2012)

dougingraham said:


> The best place for this is built into the charger. A general purpose device can't exist to do this because it can't know how to control the charger.


Most decent chargers can accept a 0-5V signal to limit the current, although a low/high setting could be easily implemented. 
Easy enough to implement on the primary side current control loop of my charger. 

This is an example of what I am looking, but I cant find it for sale (Should not be cheap either)
http://www.neweagle.net/support/wiki/images/a/a1/VPIM_rev8_specification_sheet.pdf



dougingraham said:


> I think you are worried about something that will not be a problem for you. Since you don't have a high power charger you can just set the charger you have to operate at 16 amps and you will be ok 99.9% of the time. Most of the L2 EVSE's out there can do 30 amps.


My charger can do 16Amps + the temporary drain from the auxiliary charger, which would be 3Amps for about one hour. It has priority over the main pack, so that the charging/conversion losses are supplied from the grid, not from the traction pack, whenever possible.

In the UK, Level 1 stations and household power sockets can supply a maximum of 13Amps and at home I run a long cable (I live on a second floor), so I should not run more than 8-10Amps. 

The Open EVSE does a good job reporting the maximum power but I need the charger to interpret this.


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## major (Apr 4, 2008)

cts_casemod said:


> I need to convert the EVSE pilot signal to a reference for my main charger, so that power can be throttled as required without user input, keeping the current draw within the limits of the available supply. This is what I am having trouble finding.
> 
> Maybe I am the first attempting such a thing on a converted EV?


Over here all the L1 EVSE we see are 110VAC so it's a no-brainer. But can you not simply use a low pass filter to convert the PWM signal to a reference voltage?


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## cts_casemod (Aug 23, 2012)

major said:


> Over here all the L1 EVSE we see are 110VAC so it's a no-brainer. But can you not simply use a low pass filter to convert the PWM signal to a reference voltage?


If I am to build my own circuit I'm certainly going that way. Possibly using a capacitor to block steady DC and regenerating the original signal to a 10V PWM, since the amplitude will change with status from 3 to 9V. Then it should be easy enough to have a 1-5V pilot signal to supply 6 to 30Amps. Anything over 50% duty cycle will just be clamped.


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