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. 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. It is possible to design a 20A adapter with a switch and a resistor that does not modify the duty cycle from the EVSE. This would be an unsafe adapter design. These type adapter do exist. You are correct in stating that no car manufacturer would use this type of design.
As happens many times, the discussion in a forum can get side tracked. The original discussion (I had to look at previous emails) was concerning a large NEMA plug system vs a large EVSE system for a parking area. I commented that a NEMA system would works; however, it had some issues. One of the issues was unsafe adapters usage and another was how does a vehicle with a J1772 connector know the rating of the NEMA plug. I still stand by these two issues. Unsafe adapters do exist and there is no way of preventing a person from using one in an un-monitored parking area. In addition, the vehicle cannot know the rating of the NEMA receptacle. The adapter can tell the vehicle the rating of the adapter but not the rating of the NEMA receptacle. ________________________________ From: EV <ev-boun...@lists.evdl.org> on behalf of ROBERT via EV <ev@lists.evdl.org> Sent: Tuesday, November 8, 2016 2:24 PM To: Roger Stockton; Electric Vehicle Discussion List Subject: Re: [EVDL] Cheap L2 charging in parking places: Bolt EV'sIn Production How many of these adapters are approved by the vehicle manufacturer and how many are UL listed? In addition, how many of these adapters come with a list of vehicles for which they have been tested and certificated by the UL or the manufacturer? In addition, I know of companies that are selling adapters that do not issue a pilot signal (square wave). The adapters only have a switch that show that a vehicle is connected. I guess I should not have stated "they are not safe to use". I should have stated that these adapters have not been shown to be as safe as the J1772 connectors installed by the vehicle manufacturers. Some car manufacturers like Tesla sell adapters. However, these adapters should not be used with other vehicles. ________________________________ From: EV <ev-boun...@lists.evdl.org> on behalf of Roger Stockton via EV <ev@lists.evdl.org> Sent: Tuesday, November 8, 2016 11:26 AM To: Electric Vehicle Discussion List Subject: Re: [EVDL] Cheap L2 charging in parking places: Bolt EV'sIn Production ROBERT via EV wrote: > (1) How does a vehicle with a J1772 connector know the rating of the NEMA > outlet? The portable J1772 EVSE charging cord/adapter tells the vehicle via the pilot signal how much AC current may be drawn. A 120V J1772 cord will almost certainly tell the vehicle not to draw more than 12A, so that it is safe to use on any 15A or 20A 120V outlet. I believe that some aftermarket cords may be available with a 16A pilot signal or the ability for the user to configure the cord for either 12A or 16A, however, I an unaware of an OEM cord with this capability. > One can buy a J1772 to NEMA > adapter; however, they are not safe to use. All these adapters "fake out" > the EVSE and the user must be aware of the limitations. It would not > surprise me to see these adapters outlawed. I'm not sure what sort of adapter you are thinking of. As far as I know, every OEM that offers an EV with a J1772 charge inlet wither includes or offers a 120V J1772 "opportunity charge" cord. This cord *is* a proper J1772 EVSE and not only provides an appropriate pilot signal to the vehicle, but also does not energise the charging plug until it senses that it is mated with a J1772 receptacle. I can't see how one of these NEMA to J1772 opportunity charge cords can possibly be *less* safe than an ordinary NEMA extension cord between the outlet and a charger on the vehicle. 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 ... 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