I designed and built a 'better' granny charger ('11 leaf)

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mux

Well-known member
Joined
Jan 13, 2018
Messages
350
First things first, 'better' is of course subjective. It's better for me. Namely:

  • It charges at 16A instead of 10, so as fast as my on-board charger will allow
  • It's lighter and smaller than the stock portable EVSE, most importantly: it now fits in the glove box!
  • It's got a rubber instead of PVC cable, so much less stiff and more durable, while also being slightly smaller in diameter
  • It's got thicker conductor wires (3x2.5mm2/13AWG instead of 3x1.5mm2/15AWG)
  • It's just a cable with a mains plug on one end and J1772 on the other, no big 'box' in the cable
  • I have full control over the design, i.e. I can change stuff if I want (and I will)

I did this by designing a custom controller board that fits inside an Aliexpress-sourced Duosida SAE J1772 plug. It was a proper struggle to get it all in. Nonetheless this was successful, and I've used the cable for three full charges of my range-extended 2011 Leaf, meaning it's been hanging on in freezing temperatures and ice rain for at least 24 hours. I call that a win.

https://youtu.be/HV3468LmIiQ

The cable is NOT SAE J1772 COMPLIANT. Let me just be up-front and clear about this. It will fail any sniff test, as the mains plug is more than 30cm from the EVSE control electronics. As I find this stipulation in the rules stupid, I ignored it. Otherwise, it complies with the entire charging standard; it has a GFI safety feature, it switches both live and neutral, the relays are rated over industrial temperature range for the full current, the EVSE electronics are galvanically isolated and the EVSE will latch off on car and EVSE errors. As the connector is not IP-rated, the electronics are conformally coated inside. I should probably pot the electronics.

ToDo list

I don't consider this a 'good' design yet. As you can tell from the video, fitting the board in is fine, but fitting the cables in as well is a struggle. I'm also bypassing the strain relief bracket with a generous amount of hot glue. Lastly, I have already overloaded somebody's home fuses once, as pulling 16A on a single phase maxes out our standard circuits here, and using any big consumer on that group will quickly trip a fuse. So, in a future version, I would probably want to:

  • Make the electronics even smaller
  • Make dedicated routing paths with fastening points for the high power cabling
  • Give it a switch between 10 and 16A
  • Put the LED on top, probably dual-color, bit brighter
  • pot the entire thing inside

I don't think this is viable as a commercial project. I already had to spend about €100 to make this one, which means that if I were to include workmanship and sell the thing, it'd basically be the same price as any other portable EVSE, but then very low volume and made by some schmuck on the internet who barely gives warranty. I wouldn't trust me with that. Nevertheless, if there is enough interest to warrant the time investment, I might try to do a revision and make a couple boards for people to tinker with. Not sure how many people still use granny chargers.

Also: I realize that this is a bit Eurocentric; this lead really only has any right to exist on 208/240V.
 
Where are you from? In N. America pre '13 Leafs maxed out at 12a @ L1(120v) and 16a @ L2(>200v) no matter how high your EVSE would go. Also in N. America, pre '15 Leafs all had 12 gauge wire, capable of 20a, it wasn't until '15 Nissan cheaped out and downgraded to 14 gauge or wire capable of 15a max. Of course it could be worse, it sounds like some OEM EVSEs even used 16 gauge wiring :x
 
I'm in the Netherlands, all our outlets are 240. So yeah, that makes it a lot less useful in NA. I'm aware of that.

Do you mean the gauge of the wires in the EVSE or in the car?
 
Obviously, as stated above, this project does not meet the requirements of J1772.

But, if you want a US source for this plug, we have them, however we want to be clear that we neither warrant, nor approve, of this type of a project. Injury, fire or death could result from misuse of electricity.

Consult with a qualified electrician or engineer prior to handling electricity.

https://shop.quickchargepower.com/J1772-Plug-40-Amp-JP40A.htm
 
mux said:
Do you mean the gauge of the wires in the EVSE or in the car?
The J1772 cable and power cable to the EVSE from the wall socket, not sure the gauge of wiring used in the car but as my car can charge up to 27.5a it would have to be at least 10 gauge(5.26mm2).
 
Hello,

I did a bit the same thing last summer. I put the "controlboard" in a waterproof box and used some harting plug to be able to change the cords and the plugs.
Most of what I used comes from recycling old industrial part.

https://drive.google.com/file/d/16pI3i934CtaLtJyCmwW83VUuXEbEp7NL/view?usp=sharing
https://drive.google.com/file/d/1a4t3TF6jTvQRI3GLmyj4td_CGqby41YG/view?usp=sharing

At the end, I bought 2 caps for harting plugs, the J1772 plug and the control board.
Max current is 25A because of the relay I used.

This is idiot proof too! When you change the plug, the EVSE will regulate according to the plug connected. A coding resistor in connected to the harting plug to limit the current.
For example (I'm in France, so 230V/400V) if I connect the regular house plug, It offers the the possibility to charge 8, 10 or 14A (with clear markings where to use what) via a little switch.

If I plug the small camping plug to the box, it will deliver 16A to the car.
If I plug the big camping plug to the box, it will deliver 25A to the car.
https://www.prozic.com/www2/media/P/1/P17F32A3PSOC-26810.jpg

I have plugs for regular house plug, the 2 king camping plugs (16 and 32A) and 3 phases plugs (16 and 32A) because I have it at home and some friends too plus I work in the industry so even if I used only 1phase and neutral it is very usefull.

I will try to take more pictures to explain better.

May need to say that, I know what I do, I am certified for electrical work.
 
Awesome and fancy. But I would rather have it "less fancy" and more awesome.
Put all electronics in a tiny watertight box near the plug. Have a button on the box
to switch between 10A, 13A and 16A. That box should be as big as cigarette pack.
And make it cheaper :D Also possible to make that cable 1.5mm2 (don't listen mericans,
they have fetish over massive AWG's :lol: ) as that cable in in open air. But it only matters
if there is any significant price drop or the cable diameter drops significantly (portable).
 
https://drive.google.com/file/d/15MLhyZQgumnzmGUn9kxY31HO5R3vyVdV/view?usp=sharing
https://drive.google.com/file/d/1gUAJNXkHk0Cornj4kh8tBEQA9ocd4_wK/view?usp=sharing
https://drive.google.com/file/d/1OmShvMFi0ACROHtauPV-Kjf7xYf9l3Vv/view?usp=sharing

Well, for the price it cost at the end, I can't complain.

And I can charge on any (or almost) European plug!
 
If the relays are not at the mains side (not just the length) it defeats one of the main safety principals of the EVSE, to cut the power at the source side so there is no live power on the line to the car when charging stops or during other other events, there are other issues I can see that are pretty much a potential safety hazard as well. Just like any other safety device I suppose you can make it smaller and unsafe, like stripping the insulation off an extension cord and wrapping it with scotch take to save space. This unsafe design was already done and sold in the EU a long time ago and never sold here for that reason.
 
You can't cut power "at the source". Without tripping the breaker.
This device has relays that DO cut high voltage power at the J1772 side.
And no EVSE cuts power at the source (wall outlet).
 
arnis said:
You can't cut power "at the source". Without tripping the breaker.
This device has relays that DO cut high voltage power at the J1772 side.
And no EVSE cuts power at the source (wall outlet).


Not the outlet at the EVSE box. There is a specific reason the standard dictates a short wall cord, you must cut the power at the box. The reason is because power is never to be live on the long side of the cord under certain conditions, this is one of the PRIMARY functions of the EVSE. If the relays are not at the box with a short cord then you have defeated one of the the primary safety functions of the unit. Cutting the power at the handle only addresses the arcing issue (if done correctly) when pulling the J1772. Please explain how relays in the handle prevent the main cable from having power when charging halts, the disconnect is activated, or other faults are present? You have only created an extension cord that defeats the principal design intent of an EVSE which is safety, it is no longer an EVSE it is only a extension cord that will work on an EV with reduced safety features. What you find as "stupid" is a critical part of the design. I would guess that if your unit was tested under the standards it would also fail in other areas. There are reasons for the standard and they dictate the safety architecture of the unit.
 
Why should EVSE be excessively more safer than... let's say... toaster, hair dryer or laptop charger?
Just have a functional RCCB and 16A breaker at the source and in case of any fault, no lives will be hurt.
If there is no such things for outdoor outlet, then EVSE is not the reason to blame.
One can die with OEM granny charger while plugging/unplugging granny charger to the outlet even
though no vehicle is connected. It's just slightly better to have that control box earlier in the loop.
But in terms of real "lives saved" - unmeasurable results. Compared to RCCB before outdoor outlet.

This handle charger must be waterproofed. Then it is good enough.
 
arnis said:
Why should EVSE be excessively more safer than... let's say... toaster, hair dryer or laptop charger?
Just have a functional RCCB and 16A breaker at the source and in case of any fault, no lives will be hurt.
If there is no such things for outdoor outlet, then EVSE is not the reason to blame.
One can die with OEM granny charger while plugging/unplugging granny charger to the outlet even
though no vehicle is connected. It's just slightly better to have that control box earlier in the loop.
But in terms of real "lives saved" - unmeasurable results. Compared to RCCB before outdoor outlet.

This handle charger must be waterproofed. Then it is good enough.


I'm not going to debate safety with you, it is very clear you don't understand why the standard was developed and why a toaster or laptop is not the same as an EVSE or why your design is unsafe and not just because of the long cord. Your cord design as been around a long time and was sold in the EU and was not successful because it was not safe. Let me know the next time you make toast on your garage floor or in the driveway. FYI, dogs love to chew into EVSE cords, is your GFCI EV compliant and does it cut the mains at the box? Since you live outside the US I suppose there is not much risk to you to take this position on safety. I hope you are more safe routing HV cables.
 
You are just saying it's not safe while bringing no examples who can be harmed and how can be harmed
by having HV relay closer to the J1772 end compared to wall outlet end.
 
I do see some safety issues with this type of EVSE, but nothing that is forbiden.

I installed a 2 pole relay on my EVSE, because who knows how the plug has been wired (incorrectly?).

In Europe, every public station plug is on a RCB 30mA (at least in france)... And good luck to find a GFCI plug in Europe, I'm not even sure it exists, plus the main breaker connection to the grid has one too (300, 350, 500mA or 1A), so if the ground is correctly connected no problem even if it's missing the 30mA RCD.

Let's be honest, the EVSE brick has something making it look safe so for somebody new it's better or if you want to plug to somebody's house knowing nothing about electricity.

When I plug at some friends houses, I sometimes trip the main breaker, none of them worry. Usually it's more about explaining to their family or friends that it's still normal and safe.

Don't be afraid of the electrical monster, just try to tame it!

I'm an electrician (now :D ) and with the work mux did I would probably say engineer.
 
arnis said:
You are just saying it's not safe while bringing no examples who can be harmed and how can be harmed
by having HV relay closer to the J1772 end compared to wall outlet end.

As the length of unprotected conductor grows, safety is reduced. This seems self-evident.
 
What do you mean "unprotected"? Cable is not bare copper. It is double insulated.
Firstly, each wire is insulated separately. And all wires are in another insulator+mechanical protection jacket.
Usually, EVSE cables are heavily armed (more than any extension cable/vacuum cable etc).

I don't see this DIY EVSE being any more dangerous than vacuum cleaner (except missing waterproofing for electronics).
 
arnis said:
What do you mean "unprotected"? Cable is not bare copper. It is double insulated.
.


This statement shows your utter lack of understanding of why the standard was developed. You need to read the standard completely and entirely, the FULL standard that you need to usually pay to get if you want the EVSE to pass standards, There is never supposed to be a live cable to the handle when the car is unplugged or not charging. That is the main issue with your design. There are many reasons they do this and it has nothing to do with other appliances which typically are not used daily in garages or wet locations or connected to auto chassis. I could write pages on this topic but it's pointless because you have decided the standard is pointless. Does your GFCi meet the EV spec at all levels? Does it work on a GFCI circuit? What about your disconnect delay specification? Mostly moot because it only disconnects at the handle which is the exact opposite of what it is supposed to do. Use your imagination a little and think about why they developed this standard they way it is written. You are one of several people to build these modified units and none of them could ever be sold and are safe, it they were they would be manufactured. A guy in Germany (pretty sure) did this faulty design years ago and sold them, you could have just bought one from him, he struggled to make it work but hit a wall because it never me the spec at many levels.
 
GFCI should be in the main house supply box anyway. Therefore location of disconnect relays do not matter.

People are whining so so much but almost nobody has ever died before and after that standard.

In years of EVSE use, I've never had it trip due leakage. And I've never heard it happens with others as well.
And I live in a "hell" climate in terms of moisture. Now if relay is moved closer to the handle, it changes NOTHING
in terms of leakage possibility.

Bring me some examples of real problems as well if you are so so sure that disconnect inside the handle design is
in any way dangerous (after it has been waterproofed).
If you can't explain it to to me, you don't understand it well enough.
Actually, it was more like "You do not really understand something unless you can explain it to your grandmother".
 
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