Roger, let me try to clarify my concern. A person buys a third party J1772 to NEMA adapter (made in China and made cheap). The adapter has a NEMA rated 20A plug. The adapter does not produce a modified pilot signal. I take the cord and plug from the EVSE that is rated at 50A and plug into the adapter. I take the 20A coil and plug from the charger in my converted car and plug into the adapter. The charger will not draw more than 20A from the EVSE. This is OK load wise because the EVSE can output 50A. However, it is an unsafe circuit. I have connected a 50A rated source to a 20A circuit with no interconnecting protection device. This is no different than connecting a 12AWG wire to a 50A breaker. Lets go the other direction. I have a NEMA to J1772 adapter with no pilot signal. If the cable from the adapter is plugged into a car with a 50A charger, the circuit breaker will trip (you described this situation in your email). This is an unsafe operation. A circuit bre aker is designed to protect the cable not the end load. You can check the NEC to verify this is a true statement. Circuit breaker are not used for end load protection. The end load device must have its own protection. If I have a large scale NEMA receptacle system, I cannot prevent people from using "bad equipment" or "bad configurations of equipment". If I use a EVSE system with approved equipment, these unsafe situations are minimized. This was my point when I made this statement concerning unsafe adapters and a large size NEMA plug installation.
________________________________ From: EV <ev-boun...@lists.evdl.org> on behalf of Roger Stockton via EV <ev@lists.evdl.org> Sent: Tuesday, November 8, 2016 5:36 PM To: Electric Vehicle Discussion List Subject: Re: [EVDL] Cheap L2 charging in parking places: Bolt EV'sIn Production ROBERT via EV wrote: > Again I must correct myself. I looked back at the J1772 standard and some > past work that I did. An EVSE outputs a 1KHz square wave. The duty cycle > of this wave informs the the vehicle of the maximum amperage that the EVSE > can supply (rated current). The vehicle is responsible for not drawings a > current greater than the EVSE rating. Yes. > All lower amperage adapters must > limit this duty cycle to the rating of the adapter. As an example. If > the EVSE is rated at 50 amps and the adapter is only rated for 20A, the > adapter must adjust the duty cycle. This is where you lose me. If the EVSE is rated for 50A, then it generates a pilot signal that informs the vehicle/charger that it can draw up to this amount. There is no need or purpose for an adapter between the EVSE and a vehicle unless the vehicle does not have a J1772 inlet. If the vehicle doesn't have a J1772 inlet, then it also doesn't need (or understand) the J1772 pilot signal and so there is no need for an adapter to generate a pilot signal limiting the vehicle to a lower current than the EVSE is capable of providing. > It is possible to design a 20A > adapter with a switch and a resistor that does not modify the duty cycle > from the EVSE. Yes, and this adapter is used to convert a J1772 EVSE *into* a NEMA receptacle so that a non-J1772 compliant EV/charger may be plugged into a public charging station. This is exactly the opposite of what would be required or used if NEMA receptacles were provided at each charging stall. Most of us with conversion EVs have chargers that can plug directly into a NEMA outlet, and would not need an adapter more sophisticated than an extension cord. Those of us with production EVs (other than Teslas, perhaps) will have J1772 inlets and will need to use our J1772 "opportunity charge" cords; these are effectively "smart" extension cords with a NEMA plug on the wall end, a J1772 charge paddle on the vehicle end, and a small EVSE in between that provides the appropriate pilot signal for the vehicle/charger. If the NEMA plug on the wall end of the opportunity charge cord is a NEMA 5-15P, then the pilot signal should (must!) tell the charger not to draw more than 12A. If the cord has a NEMA 5-20P plug, then the pilot signal can allow the charger to draw up to 16A (since this plug can only mate with a receptacle on a 20A rated circuit). Even if the J1772 opportunity charge cord were to tell the charger it is OK to draw more current than the NEMA receptacle and circuit are rated for, there should be no safety issue: the NEMA receptacle and its associated supply wiring will be protected by an appropriately rated breaker and the breaker will simply open. Cheers, Roger. _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org EV -- Electric Vehicle Discussion List - lists.evdl.org ...<http://lists.evdl.org/listinfo.cgi/ev-evdl.org> lists.evdl.org The Electric Vehicle Discussion List is a forum for discussing the current state of the art and future direction of electric vehicles (EVs). We define an EV as a ... Read EVAngel's EV News at http://evdl.org/evln/ EVDL EV News Archive - Electric Vehicle Discussion List<http://evdl.org/evln/> evdl.org EVLN - EV News Archive Edited by Bruce {EVangel} Parmenter: EVLN: home | help | archive | news | privacy policy | terms of service Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA) [https://s1.yimg.com/dh/ap/default/130909/y_200_a.png]<http://groups.yahoo.com/group/NEDRA> Yahoo! Groups<http://groups.yahoo.com/group/NEDRA> groups.yahoo.com / -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20161109/bc09e762/attachment.htm> _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org Read EVAngel's EV News at http://evdl.org/evln/ Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA)
