The possibility of a kit for a Level 2 EVSE

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pgrovetom

Well-known member
Joined
Jun 23, 2010
Messages
75
I'm curious among the people who feel capable of both doing wiring and building simple electronic kits, what would the interest level be in just building your own EVSE and installing it? If all of the AC path items such as the NEMA box, 240VAC GFCI, relays, and the chord/J1772 receptacle could be bought, controlling those would avoid most UL issues since they are all UL approved already as purchased. I'm not sure of the UL requirements for a home self built and installed system would be? If one has the time and enjoys it, I'm just guessing but it shouldn't cost more than $400-$500 installed if you do it yourself. I believe if I could find the J1772 connector at a reasonable price, its very doable. Opinions? Interest?
 
I am also considering such options, watching for suitable parts, and for the first Level 1 EVSE available to purchase.

The NEC625 says something like the parts and system need to be "listed", presumably for the intended use. Or, something similar.
 
I am also interested in building from a kit. If you have information of available parts and instructions pls share! :)

Thx.
 
I'm just looking at it but it looks pretty straightforward.

Basically what I'm thinking about is a NEMA box with off the shelf 40A 240V GFCIs available for pool and other applications, then followed by optically coupled Solid State Relays to shut of the 240V when the Pilot tone state is such. A small lump UL approved power supply would pull isolated 5V and 12V off one leg of the 240VAC and power a small micro-controller board. Then I would write some simple basic or C code to generate the 1KHz tone and control its duty cycle. The micro would also turn the SSRs on and off, light some LEDs ( like on most commercial units) and have a switch to indicate Level 1 12A, Level 1 16A, Level 2 32A. It would be wired to your panel via THHN #8 wire inside EMT and terminate in the box on the GFCIs. Then the GFCIs would be connected to the SSRs and they would go to the 20 foot flexible #8 and smaller control wire as per the spec. The micro board would be floating and drive the pilot and SSRs optically isolated. The code to monitor the EVSE state on plug-in, control the 240VAC and send the appropriate duty cycle would be simple. One can buy a micro board for $29.95 with breadboard area for some opto-couplers and the interface circuitry. Other than finding the J1772 connector itself and its cable and choosing and programming the micro, its not that complicated.
 
And ... what you want is a PORTABLE EVSE:

I know of a brilliant electrical engineer. His name is Martin Eberhard. :p

He had similar thoughts. (Great minds think alike ? ;) ).

It's a great design. Robust hardware. Works with both 120V and 240V, up to 40A. Incorporates some nice fundamental design ideas -- for example, swappable pig-tails which tell the electronics what current to expect (instead of a user switch) based on the type of receptacle plugged into. Does need some adjustment for LEAF, since pilot signal at 120V defaults to 16A (need to provide a 12A option). Includes thermal sensor in pigtail. I provide these links on an AS-IS basis for reference only -- disclaiming any liability for passing on these posts. Use the info at your own risk ... but it could be a good starting point.

http://www.teslamotorsclub.com/showthread.php?t=2889

http://www.teslamotorsclub.com/showpost.php?p=38252&postcount=106

http://www.teslamotorsclub.com/showthread.php?t=3099
 
LEAFer said:
And ... what you want is a PORTABLE EVSE:

I know of a brilliant electrical engineer. His name is Martin Eberhard. :p

He had similar thoughts. (Great minds think alike ? ;) ).

It's a great design. Robust hardware. Works with both 120V and 240V, up to 40A. Incorporates some nice fundamental design ideas -- for example, swappable pig-tails which tell the electronics what current to expect (instead of a user switch) based on the type of receptacle plugged into. Does need some adjustment for LEAF, since pilot signal at 120V defaults to 16A (need to provide a 12A option). Includes thermal sensor in pigtail. I provide these links on an AS-IS basis for reference only -- disclaiming any liability for passing on these posts. Use the info at your own risk ... but it could be a good starting point.

http://www.teslamotorsclub.com/showthread.php?t=2889

http://www.teslamotorsclub.com/showpost.php?p=38252&postcount=106

http://www.teslamotorsclub.com/showthread.php?t=3099

Based on the Tesla's portable EVSE, would you be able to estimate how much it would cost for a similar one for the Leaf?

Thx.
 
mxp said:
Based on the Tesla's portable EVSE, would you be able to estimate how much it would cost for a similar one for the Leaf?

Thx.
I am aware that Martin sold it close to cost for around $800, which excludes the Tesla Charge Port connector (good, because it's expensive and we need to substitute with J1772 anyway), but also includes several "pigtails" (the Marinco California Standard versions are expensive items), but I don't know which or how many that $800 includes. Surprisingly evcomponents shows a $750 price, which I would have expected to be higher (a 20% profit?), but then again it only shows 3 pigtails. (Again the Tesla connector is not included, because the part is just about impossible to obtain, and the customer is expected to provide it for the "upgrade" from the Tesla MC120 they already have.)

So ... somewhat of a guess, but drawing on facts I have ... I'd say $500 for a 25' version with a single pigtail (let's say NEMA 14-50, the most popular for RV parks), including the J1772 plug on the other end (for which I don't have a price but assume $50). Add almost $75-$100 for another pigtail, maybe for a dryer outlet, (because it's widely available), NEMA 10-30 or 14-30.

But which dryer outlet to choose ? :? And in the Midwest there are others in use. And you might want a 10-50 (welding) option ... That's where the pigtail flexibility gets expensive, because you can't always anticipate what receptacle you might "meet" on the road.

Hope this helps.
 
All the home-brew and "kit" talk is great for education, but illegal (without UL listing of the completed system) to use for EV charging.

Also, there are dangerous, even deadly) voltages and currents involved, so PLEASE be careful.

Part of the UL evaluation, I believe, is failure-mode hazards.
The question is usually, if any one component (or sub-section) fails in any way, will the power be removed from the "charge-plug" and cable?

Another UL issue is: what happens if the "exposed" parts are rolled over by a car, or the car rolls away?

A third UL question is: what are the shock and fire risks, for the probable environment and uses?

How did a toaster ever get UL listed?

So, again, safety and FIRE danger are two VERY important issues. Use EXTREME Caution, PLEASE.
 
For example, a UL listed EVSE might have TWO relays, just in case one fails to open.

The u-processor might need to produce a continuous string of pulses to try to "close" the relay(s), so that if the processor dies or freezes, the relays will open.

Etc., etc. ...

So, making something work is not difficult, but being properly fault-tolerant is a whole different issue.

An extension cord with a J1772 connector and a "trick box" attached ... would probably "work" ... but, of course, for emergencies only. :)
 
For example, a UL listed EVSE might have TWO relays, just in case one fails to open.

The u-processor might need to produce a continuous string of pulses to try to "close" the relay(s), so that if the processor dies or freezes, the relays will open.

Etc., etc. ...

So, making something work is not difficult, but being properly fault-tolerant is a whole different issue.

I spent 25 years in Telecom System design and was directly involved and or supervised many UL certifications and fault tolerant designs. UL is not as stringent as one might expect. All the components in the 240V line can be purchased pre-UL certified such as the GFCIs and Omron SSRs. The SSRs come with optically isolated control. That means the electronics that controls the solid state relays is floating relative to ground with greater than 600V isolation.

I have never seen UL require something like redundancy. In Telecom, we designed everything to a myriad of standards and redundancy and fault tolerance was provided to keep the MTBF at some very low level. The reason had less to do with safety than with keeping service running. Your old telephone required 99.9997% up time. That basically means everything is duplicated as a backup and its MTBF is longer than the MTTR. That means its time to fail is much longer than the time to repair. UL never cared about that. They only cared about safety in AC circuits primarily. Safety in the AC arena as with UL was accomplished with proper isolation and design. If the underlying AC components such as the box, GFCIs, SSRs and connectors are UL approved and UL approves the control isolation, UL certification is straightforward since nothing else appears in the AC path except wiring. Designing a GFCI or SSR used with 240VAC from scratch would require more UL scrutiny but UL would mostly concern itself with the wiring and the J1772 coupler is already certified. I agree 120VAC and or 240VAC is dangerous but every appliance you buy from toasters to the computer and its monitor here are UL certified. It just requires care. If someone is not educated than they should not be messing with it.

The disconnect relays in the EVSE are already a form of redundancy. They disconnect the AC from the plug until it's engaged. No other piece of equipment in Europe where 240VAC is common disconnects the AC. Most electric shocks are due to the earth ground reference. 240VAC is just two out of phase 120VAC so the voltage to earth is the same from either leg. The GFCIs carefully monitor the neutral versus earth current and quickly disconnect the AC if they sense earth current that might be flowing through someones body. That means the J1772 system has 3 levels of safety already. If you grabbed your toaster while it was toasting while standing on a wet floor, it would be just as dangerous. As long as your kitchen GFCIs worked, they would protect you. Its very difficult to get your body across the 240VAC which is referenced across the two legs.
 
All the home-brew and "kit" talk is great for education, but illegal (without UL listing of the completed system) to use for EV charging.

Other NRTL listings are legal such as ETL. But yes, building your own charger is not legal. Do so at our own risk.

Also, there are dangerous, even deadly) voltages and currents involved, so PLEASE be careful.

Yes these voltages can kill you.

Part of the UL evaluation, I believe, is failure-mode hazards.
The question is usually, if any one component (or sub-section) fails in any way, will the power be removed from the "charge-plug" and cable?

NRTL labs such as UL or ETL look at failure modes but redundancy is not required. UL or ETL will certainly be happy with redundancy or going beyond the standards but they don't go as far as a subsection failure.
Another UL issue is: what happens if the "exposed" parts are rolled over by a car, or the car rolls away?

UL or ETL would look at something obvious like this. In most cases a GFCI covers dangerous cases such as this but the coupler design would probably need to be recessed but the relays are above and beyond what UL or ETL would insist upon. They like it!
A third UL question is: what are the shock and fire risks, for the probable environment and uses?

Yes
How did a toaster ever get UL listed?

I totally agree but they do every day. UL and ETL are not as draconian as one might think. They aren't cheap! How did microwaves get approved when placing metal inside can explode? They try but let many things get by.

So, again, safety and FIRE danger are two VERY important issues. Use EXTREME Caution, PLEASE.

Agreed. Any electrical wiring of AC must be done to NEC code requirements and components must be NRTL lab approved.
 
Keeping in mind that UL or ETL or similar NRTL listing is required for safety and legal reasons, it may be possible to get very close legally.

The primary safety issues revolve around the 240 VAC path from the panel board wiring through the following path:

A 2 pole 240 VAC GFCI rated at 40A with a power present indicator
then
a 240VAC rated UL listed isolated power supply ( like for a laptop) that produces +5V and +/-12V
An isolated 240 VAC switch for disconnect
then
The 25 foot charging cable with a J1772 receptacle installed

( need to get from someone like http://www.northwire.com/ev-cable-solutions.php )

Then the 240 VAC switch must be controlled based on the pilot signal state

The pilot signal must be produced as a +/- 12,9,6, 3, 0 volt 1KHz square wave as per J1772

The proximity pin must be terminated as per J1772

Ok so here is a first very gross simple prototype

One can use a Square D SPA HOME250SPA which is a Nema/UL listed 50A 240 VAC GFCI

http://www.aplussupply.com/break/sqd/homeline/boxes/box.htm

That can be followed and properly wired to a commercial 240 VAC remote disconnect box such as:

http://www.smarthomeusa.com/ShopByManufacturer/ELK-Products/Item/ELK-9200/

This in turn can be controlled by a small micro-controller evaluation kit such as:

http://www.ti-estore.com/merchant2/merchant.mvc?Screen=PROD&Product_Code=TMDXDOCK28027

Here is a video describing its use:
http://www.ti.com/corp/docs/landing/piccolotools/index.htm?DCMP=Piccolo&HQS=Other+OT+controlstick

The experimenters board at $79 has room for the +/- 12,9,6,3,0 signal conditioning with a simple OP AMP driven by the Micro PWM
It can also control the 240 VAC switch and provide the LEDs and any other I/O desirable such as the 12A/16A/32A selection switch.

Its pretty easy to modify the C code on the demo actually provided to provide all the logic and PWM required to meet the J1772 state diagrams.

The 240 VAC path will have been UL or ETL listed by Square D or the switch manufaturer and it's wired like any home by an electrician to code.

The one caveat is NEC 625 requires the disconnect switch function so that piece will not be UL or ETL listed so its not legal.

If you have electrician skills or training, its safe just like when a home is wired using UL/NEMA listed devices and the electrician is trusted to follow the code but this is still not technically legal since the disconnect function has not been tested by a NRTL nor has it been FCC compliance tested.

Just fun to explore how it might be done and what it might cost.
 
My $0.02 worth:

There is no doubt that electricity can be dangerous, even lethal, whether we're talking about 120V or 240V. Those who do not keep that danger in mind are prime candiates for a Darwin Award.

Nonetheless, I opine that, when it comes to plugging and unplugging 240V appliances, the SAE, NEC, and UL allow paranoia and fear to trump common sense --and even the statistical evidence.

For example, those organizations do not have a problem letting Winnebago and boat owners plug into 240V outlets at RV parks and marinas. Yet EV drivers are just too "stupid" to do so safely? It makes no sense.

Their assertation that it is just too "dangerous" prompted me to gather statistics from countries that use 240V as a standard. Are there, in fact, more deaths from electrocution in such countries?

I managed to find such statistics for Australian/New Zealand over a 10-year period (1992-2001) and compare them with those for the USA. The findings?

  • A yearly average of 1.95 deaths by electrocution per million in Australia/New Zealand.
  • A yearly average of 1.87 deaths by electrocution per million in the USA.

That's right: .08 more deaths per MILLION annually for those "down under" who have to plug and unplug with a "dangerous" 240V system every electric appliance that we use with 120V: hair dryers, coffee pots, shavers, curling irons, mixers, vacuums, computers, electric heaters, drills, leaf blowers, lamps, etc., etc., etc.

The difference is statistically negligible.

Consequently, I am convinced that --sooner or later-- 240V "mobile charging kits" will become a common EV accessory --despite the paranoia of the SAE, NEC, and UL. It makes me wonder just how easy it might be to take the J1772 plug off the Leaf's 120V "emergency" cable and splice it into a Telsa Universal Mobile Charging Kit.

leaf_cable.jpg
chargingSolutions_med_main1.jpg
 
That difference can be explained by the fact that they drink far more in Australia and not a result of 240:)
 
Yanquetino said:
My $0.02 worth:

... Nonetheless, I opine that, when it comes to plugging and unplugging 240V appliances, the SAE, NEC, and UL allow paranoia and fear to trump common sense --and even the statistical evidence.

For example, those organizations do not have a problem letting Winnebago and boat owners plug into 240V outlets at RV parks and marinas. Yet EV drivers are just too "stupid" to do so safely? It makes no sense.

Their assertation that it is just too "dangerous" prompted me to gather statistics from countries that use 240V as a standard. Are there, in fact, more deaths from electrocution in such countries?

I managed to find such statistics for Australian/New Zealand over a 10-year period (1992-2001) and compare them with those for the USA. The findings?

  • A yearly average of 1.95 deaths by electrocution per million in Australia/New Zealand.
  • A yearly average of 1.87 deaths by electrocution per million in the USA.

That's right: .08 more deaths per MILLION annually for those "down under" who have to plug and unplug with a "dangerous" 240V system every electric appliance that we use with 120V: hair dryers, coffee pots, shavers, curling irons, mixers, vacuums, computers, electric heaters, drills, leaf blowers, lamps, etc., etc., etc.

The difference is statistically negligible.

Consequently, I am convinced that --sooner or later-- 240V "mobile charging kits" will become a common EV accessory --despite the paranoia of the SAE, NEC, and UL. It makes me wonder just how easy it might be to take the J1772 plug off the Leaf's 120V "emergency" cable and splice it into a Telsa Universal Mobile Charging Kit.

leaf_cable.jpg
chargingSolutions_med_main1.jpg

I'm not advocating one way or the other, but am trying to understand why we have an apparent limitation. I lived in England for 4 years and Germany for 3 and can confirm that while I HAVE been shocked using a 120V outlet here in the 'States, that never happened to me in Europe.

When we suggest someone is forcing us to skip the plug because it's too dangerous I have to ask HOW DO WE KNOW? Have we absolutely found the requirement that forces the L2 EVSE to be hardwired?

That being said, this is a meaningless comparison because when we're talking about using a L2 EVSE in the US, we're talking about a spec that tops out at 240V and 80A - not a 240V 13A wall outlet.

I don't think it's a direct comparison with RVs in the US either as the largest RV connector I can find retail, and the largest connector I found in a quick look at some larger RV parks is 50A, while most are 30A.

I agree that we'll have DIY portable L2 EVSE in use, but I don't expect we'll see commercial units because the EVSE manufacturers are under the impression that they must be hardwired. The J1772 spec is a North American spec - not just US.

I don't expect that we will be able to use a Tesla EVSE until they change their cars to J1772 and start selling compliant EVSE.
 
I have seen the 80A mentioned a few times now ... and am compelled to comment.

Yes, the spec allows up to 80A. But does not require it. And notice that the UL Listing is limited to 30A for the current J1772 connector. Personally I'd be happy (in the short-term) with a EU equivalent 13A/230V = 2.99kW portable EVSE. So ... the "danger" would be the equivalent of the EU "danger" -- perceived or real. I am NOT suggesting an 80A portable (plug-in) EVSE. I am not even asking for a 50A one either. But 6.6kW would be nice. That would mean drawing 27.5A at 240V. (And willing to compromise down to a standard 30A breaker, or pulling only 30*80%=24amps=5.76kW. Hey! That's like a dryer outlet ! :eek: using NEMA10-30R or NEMA14-30R)

(BTW, the Tesla portable EVSE pictured above is limited to draw 40A from a NEMA 14-50R (RV style) receptacle and contains a GFCI.)
 
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