# J1772 chargers for DIY



## Coulomb (Apr 22, 2009)

J1772 ports aren't chargers, they're just glorified general purpose outlets (power points). So you are charging with your own charger. The only negotiation that happens is the J1772 says how much power it has available, and you're not supposed to take more than that.

If you have a ~2 kW charger, you'd be pretty safe just charging as normal, perhaps dropping to about half power if the J1772 pilot says 6 A maximum. (At the low end, the signals are 6, 9.6, 15... A AC, usually at 240 V AC, so only the lowest end (1.44 kVA) is likely to limit you).

Even with a fast charger, the vehicle nominates the voltage and current at every point in the charge cycle, so the battery should never get overcharged.

There are gizmos that convert J1772 at one end to an ordinary power socket at the other end, doing the J1772 negotiations for you. So you don't even need to build it into the car if you don't think you'll use public charging all that often. Just pack the gizmo when you think you'll need it.


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## Caps18 (Jun 8, 2008)

The maximum amperage is 30A (or is it 40A?) at 240V from level 2 EVSEs.

I did hook up a J1772 outlet into the AVC2 device, the main power cables go right to the charger though. The AVC2 does the handshake, and it works. It is up to the charger to output the correct voltage to charge the batteries, and to be able to accept the 240V input from the Level 2 charging EVSE.


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## MathisLaurant (Feb 21, 2017)

Sorry for the late reply...

I thought that the charger was in the infrastructure unit. 

I've attached a very crude drawing, is this how it would be?

The on-board charger will recognize when the desired voltage of the battery pack is reached and stop charging. It only would pull the amount the charger is set for, depending on what type of charger of course, correct? 
So if the charger is set to charge at 96v and 5A to the battery pack it will only pull that much from the source. 

please correct me if I am wrong

Note: 
To the left of the dotted line is the charging infrastructure. 
And to the right is the vehicle/motorcycle.


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## cmcnall (Aug 12, 2015)

I use an AVC2 device (google it and it will come up) on my bike.
It is used on the handshake line of the J1772 connector to create the OK signal and allow power contacts to close on the EVSE or wall mounted plug.
My plug was from a nissan leaf
The power lines of my J1772 connector then go to a pair of Meanwell 48V Constant current power supplies with the output in series and diode protected.
Those then go through a solid state relay.
The relay is powered off a programmable voltage panel meter that turns the relay on when battery voltage is lower than full. The panel meter is powered off my DC/dc controller when the bike is on. and also powered off a 12V power supply also hooked to the J1772 connector so when the bike is off and charging the power meter has power to keep the relay latched.
In my setup the AVC2 is always on powered off the DC/DC converter as it uses very little power overall.
Good Luck.


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## classicevs (Dec 14, 2015)

Hello I searched and this thread sounds closest to my question so hopefully somebody with the knowledge can help me (Thanks In Advance!  I have a few year old Prius plug in and I want to add power to the battery bank via *solar panels* on top of my car port when it's parked all day (I take the bus to work and I live in a very sunny part of the country it's parked all day so hoping to utilize 'free' energy  I don't currently have a solar home system and don't have the $ for that right now.

I plan to use as small as possible, yet still adequate, charge inverter (thinking a 1500w pure sine like this one on Amazon http://a.co/bt9mgZ0) coupled with a J1772 120v adapter similar to this one http://bit.ly/2HdHSga, and approx. 1000w of panels that will output approx. 18v (they come with their own solar charge controller).

According to this site:

"Level 1 Charging

This is the slow charging route that uses a standard 120 volt power outlet. Electric cars sometimes have the option of designating either a flow rate of 8 or 12 amps…The difference between 8 and 12 amps is the higher amperage rating will charge your car faster. 8 amps is like a trickle charger you can plan on three miles per hour." (http://www.evelectricity.com/charging/) [Note: my Prius has option select either 8 or 12 amps]

The 200w panel (5 of them) I'm looking at specs are: Output power / Amp / hour = “16.12 amp”

and the WindyNation VertaMax Pure Sine Wave 1500w Inverter says will "convert battery power to 115 - 120 VAC household power"

and I found on this site re: the Prius plug-in specifically:

Bob answered about a year ago

The 120 volt chargers draw about 12 amps. maximum. A standard 15 amp circuit should be fine. 20 amp even better. The circuit should be for the charger ONLY as the current draw is pretty near the maximum of a 15 amp circuit.

Joe answered 5 months ago

Don't know about previous years, but I just got a 2017 and under vehicle settings/ charge settings you can choose 8 amp or max amp charging. I had my circuit breaker trip twice, switched to 8 amps and the problem is fixed (https://www.cargurus.com/Cars/Discussion-c24260_ds744077)

I'd prefer to just 'trickle' (again I'll be at work all day so not in a hurry) directly from the panels through the 1500w inverter thru the J1772 120v adapter plugged into the car J1772 port to the onboard batts (as detailed in image in this thread above)

Naturally I definitely don't want to damage my onboard bank, so my question is: if the amount of power produced from the panels while plugged in during the day ever falls below 8 amps (for example, the weather turns very cloudy) will it just not 'transfer' that charge/do anything?

Again any help is much appreciated! Thanks


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## Kevin Sharpe (Jul 4, 2011)

classicevs said:


> a J1772 120v adapter similar to this one http://bit.ly/2HdHSga


This EVSE will expect a AC power supply of 120V 12A as a minimum because thats how much current it's telling the car to take from the inverter. I suspect your inverter will shutdown with an over current warning when you drop below 12A from your solar system.

What you really need is a EVSE that varies it's output as the input power varies. This is easy to do technically (you just vary the PWM "pilot signal" as the solar power varies) and I would begin your search by asking the question on the OpenEVSE forum (here). For reference the J1772 standard supports charging down to 6A


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## classicevs (Dec 14, 2015)

Kevin Sharpe said:


> I would begin your search by asking the question on the OpenEVSE forum (here). For reference the J1772 standard supports charging down to 6A


Thanks very much Kevin for taking the time to respond I will do that and post on there THX! - Mike


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## Coulomb (Apr 22, 2009)

Kevin Sharpe said:


> What you really need is a EVSE that varies it's output as the input power varies. This is easy to do technically (you just vary the PWM "pilot signal" as the solar power varies)...


It would not be the EVSE varying its output, it would be the charger varying its load. It's not clear to me whether any pilot PWM factor between the one for 6 A (10%) and the one for 9.6 A (16%) has a defined current limit. In other words, it's not clear to me whether you can expect a charger to respect a continuously varying PWM and cause a continuously varying load.

Even if that's how some chargers interpret the standard, it's not obvious that every car charger would do so. My guess is that many chargers would measure the PWM and "bin" it (as in throw it into the bin that fits best) as "near 10%" or "near 16%" or near the other 4 defined PWMs.

In yet other words: are the current limits analog (continuous) or digital (~6 discrete values)? For solar charging, it would be wonderful if the current limits were continuous, and even extended down to say 3 A and 5% PWM.


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## Kevin Sharpe (Jul 4, 2011)

Coulomb said:


> It would not be the EVSE varying its output, it would be the charger varying its load.


That is correct... the EVSE 'tells' the car charger the maximum current that it can draw based on the analog PWM signal, or digital value if it's in digital communication mode (digital is not supported by most EVSE).



Coulomb said:


> Even if that's how some chargers interpret the standard, it's not obvious that every car charger would do so.


Our Charging Stations had a solar mode where you could vary the pilot signal PWM based on an external stimulus (or software command). In our testing every OEM vehicle reliably tracked the maximum current commanded from 6A to the cars maximum (usually 16A or 32A) with only the Tesla Roadster refusing to charge at 6A (we suspect this is a Tesla software bug because the car charges fine from 7A) 

Lots of OEMs have EVSE that allows end users to select different maximum currents to match the wall socket they are using... Chevy, Tesla, and even the latest Leaf (iirc) EVSE have selection mechanisms.

This feature is also used extensively in the new breed of Charging Stations that allow the electricity supplier to dial down the EV charge rate in return for bill discounts 

If it helps, here's a useful page from the relevant IEC standard (note PWM below 8% or 6A commands digital communication mode).


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## steveob (Nov 10, 2017)

my leaf draws 12 amps, using a 240v modified portable evse, 12 amps isn't in the typical j1772 buckets. I could use those other 3-4 amps amps though, but haven't bothered.


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## Kevin Sharpe (Jul 4, 2011)

steveob said:


> my leaf draws 12 amps, using a 240v modified portable evse, 12 amps isn't in the typical j1772 buckets. I could use those other 3-4 amps amps though, but haven't bothered.


OEM EVSE's are dialled down to provide a safety margin... for example in the UK wall sockets support 13A 240V but the Leaf EVSE commands the car to use 10A 240V


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## steveob (Nov 10, 2017)

did anything ever become of the digital (specifically 5% using pilot for comm) side of it? I'm not "give SAE $1800 and go fish" curious, just in a practical sense.

as long as the charger responds to the mppt command the evse doesn't matter (as long as it doesn't overthink the charger amperage consumption), but it is a convenient hacking spot for this situation. 

Though 6 amps might not be small enough to make an effective mppt. might be best to command the charger more directly than relying on pwm duty cycle to command it, since < 6 amps is verboten without other means.


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## classicevs (Dec 14, 2015)

Thanks much for additional input Kevin and steveob - fyi Kevin I've tried contacting OpenEVSE a few times but they haven't responded if they can help yet - maybe they're busy. So steveob you're saying the minimum charge your Leaf will recognize/receive is 12A? See attached photo my Prius plugin has slow 8A option yours doesn't? So do either of you know if I can harm my onboard bank if I hook up my J1772 120v linked above to my Prius hooked up to solar (actually looks like I'm going to go with 475w now) via that 1500w inverter if the power drops below 6A? Will it do anything? If it could harm it (of course definitely cant risk damaging onboard batt bank nor onboard charger) do you know if adding auxiliary batts between the panels and 1500w inverter could alleviate that so the aux batts are charged first? (*I'd prefer not tho to keep cost as low as possible) There's gotta be a way to do this just trying to figure it out Thanks!


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## Kevin Sharpe (Jul 4, 2011)

steveob said:


> did anything ever become of the digital (specifically 5% using pilot for comm) side of it?


It's used by the CCS system and I suspect CHAdeMO/Tesla Supercharger as well (I'm not up to speed on the physical implementation of these two fast charge standards).

If you are interested you can get access to the CCS Specifications for free on the CharIn website (here) but you'll need to pay for the underlying standards if you want to dig really deep.


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## Kevin Sharpe (Jul 4, 2011)

classicevs said:


> So do either of you know if I can harm my onboard bank if I hook up my J1772 120v linked above to my Prius hooked up to solar


The charger in your car will try and take 8A (if that's the setting you're using) from the solar system. If you are generating 8A then everything will work fine and the battery will charge. If you are generating less than 8A the car will still try and take 8A (because that's what you've old it to do) and will probably pull the inverter offline stopping the battery charge. It's unclear exactly what will happen then... probably the inverter will recover (because you removed the charge load) and the car will start charging again, only to trip out again 

While this constant on/off cycle of the charging will not hurt the battery it may damage the contactors which are designed for a limited number of switching cycles.


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## Kevin Sharpe (Jul 4, 2011)

classicevs said:


> There's gotta be a way to do this just trying to figure it out


Most people simply connect their EVSE and solar array (via an inverter) to the house electrical system. Then they select a low EVSE current (8A in your example) and charge the car during the middle of the day. While this does not guarantee you are driving on 100% solar it is a very simple and robust solution.

Alternatively, if you have some serious money to spend then using a large battery as your charging source is another option... see EVTV Selfishly Solar (here).


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## classicevs (Dec 14, 2015)

Kevin Sharpe said:


> Most people simply connect their EVSE and solar array (via an inverter) to the house electrical system....
> 
> Alternatively, if you have some serious money to spend then using a large battery as your charging source is another option...


Thanks again Kevin. As I said above I don't currently have house solar, and yes like I said naturally anyone would want to try to do this at lowest cost possible, but more importantly for me will be the weight if I try to take this mobile (heavy would defeat the purpose/any potential gains). It sounds like what I need to find is a solar controller that can be programmed to only 'switch on' at 8A minimum, and turn 'off' if ever falls below? Searching just now I found this SOLAR BOOST CHARGE CONTROLLER WITH MPPT
I don’t know enough about this type of hardware, unfortunately, but this device sounds like it could be what I’m talking about for ~ $100? 
“Most solar charge controllers move power from a higher voltage panel to a lower voltage battery bank. The GVB-series controllers, in contrast, pump electricity up hill. These controllers will take a lower voltage panel and boost the voltage to charge a 24V, 36V or 48V battery pack. In fact, the GVB's will work with almost any panel that's below your battery voltage. Larger panels are cheaper per Watt than smaller panels, so using one large panel and a boost controller results in a significantly lower system cost than smaller panels in series with a conventional charge controller.” 
“Maximum Input Short Circuit Current: 8A” “Maximum Input Current: 15A” https://genasun.com/all-products/solar-charge-controllers/for-lead/gvb-8a-pb-solar-boost-controller/

So if saying 'maximum Input Current: 8A' I'm assuming that means it won't 'turn on' / let power flow through below that? I'll ask the company to be sure...

So sounds like if I connect the 550w panels (that's the most I can max out for the surface area) in *parallel* I’d get max potential of 29.6A (for the configuration I’m thinking I could use four 100w panels at 5.5A max each, and two 75w @ 3.8A each), so that should be more than enough for Prius plugin charging?

And a ‘workaround’ ‘solution’ could be for me to only connect when forecast says a sunny day (at least ‘partly’ sunny – panels typically should still produce power) – but don’t bother on rainy/overcast forecast?

Thx again sounds like we're getting close 

Edit: whoops correct that! On 2nd thought in order to use [minimum] Level 1 J1772 I’d need ~ *110v* minimum, correct? So at these 550w of panels, in *series* I could get max 110.8v _at max power_ Hmm… that’s probably cutting it too close… :\ I think the absolute ‘max’ I can configure (for the surface area I have for ‘mobile’) is ~600w which would come out to just over 120v max – ok - but in *series* that would be only ~ 5.5A (avg rated amps for the panels) Argh! :\ Soo… sounds like I’ll need to get V up to ~120v _minimum_, while amps above 8A minimum at the same time? :|

Edit#2 just found this:

"A Solar Panel Powered Electric Vehicle Charger?"

The DC-AC Inverter
A 12V to 110V inverter is probably the most common one available, widely used to convert the car battery from 12v to 120V.

Each solar panel produces 120W (15 volts x 8 amps). When converted to 120V, we get less than one amp! (120 volts x 1 amp = 120Watts). To have as much amperage as a typical 15A, 120V circuit, we would need 15 panels.

If we use three 12V 100AH batteries ($225 ea.), we could generate about 15A for 20 hours at 12V. But this is only 1.5A at 120V!...http://www.deleogarages.com/ev/

back to the drawing board :\


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## Kevin Sharpe (Jul 4, 2011)

classicevs said:


> I think the absolute ‘max’ I can configure (for the surface area I have for ‘mobile’) is ~600w


If you set the charging rate to 8A in the car then you can use the standard 12A EVSE that is supplied by Toyota (the car setting overrides the EVSE setting).

When set to 8A in the car you will require an inverter and solar system that can *sustain* a power level of at least *1000W* (8A x 120V = 960W).

The system you require will be larger than 1000W because you need it to work for several hours a day at various locations. No point having a system that only works for 10 minutes at high noon 

I suggest you have a chat with a solar professional and ask them to scope out a system that will meet this requirement. A lot will depend on your location because the amount of solar varies a lot by location, TOD, season, weather, etc.

I suspect you are about to find out that small/mobile solar systems do not charge EV's very well and that's why none of us have them


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## classicevs (Dec 14, 2015)

Thanks Kevin I think I was editing my post above about the same time you replied the same had to occurred to me 



Kevin Sharpe said:


> I suspect you are about to find out that small/mobile solar systems do not charge EV's very well and that's why none of us have them


Well, where there's a will... I'm going to try


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