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NACS Cabling

Whelp.  With CCS dying in the US. We *really* need OpenEVSE to source an NACS cable or connector for existing OpenEVSE units.


https://www.youtube.com/watch?v=BfrgG8MmrLI




Just opening the discussion. :-)

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I've been holding off on buying an OpenEVSE for the past few years as I waited for someone to start selling a NACS cable.  As soon as I heard that Tesla had opened the standard for NACS, I figured that might finally be the catalyst for someone to offer the cable.  Now with Ford and GM (and likely more to follow) saying they'll use NACS, the ball is well and truly rolling.  Does anyone know how much longer we might be waiting for a cable?


I've been tempted to buy a salvaged Tesla mobile connector from eBay to use the cable, but they're all so expensive for something that doesn't work, particularly considering their relative cost to purchase brand new.  Plus, I'm a little hesitant to re-use something that may be damaged in a high voltage/amperage application.

Technically, there's no reason a NACS cable can't wire directly up to an OpenEVSE unit.    Tesla converted them over to more standard J1772 / CCS signing a few years ago.


However, the supply of NACS cables is non-existent at the moment.  Nobody is making them (which is a bit concerning with this industry shift).


We really need a supplier to step up.  Obviously if your vehicle has a J1772 / CCS plug, it doesn't make sense to source an OpenEVSE with the NACS connector... however in 2025/2026 this is supposed to shift rapidly.  OpenEVSE should be ready.

image


Signaling seems to be identical to J1772 from what I can tell.  (PP vs CP)

image


(From the standard at https://tesla-cdn.thron.com/static/HXVNIC_North_American_Charging_Standard_Technical_Specification_TS-0023666_HFTPKZ.pdf

OpenEVSE will offer NACS as soon as we can find a supplier. Tesla cables sacrificed from a Tesla Mobile Connector or HPWC work perfectly on OpenEVSE.

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Don't those NACS connectors handle AC or DC depending on the evse or charger?  seems dangerous to not totally isolate the AC and DC connections like a CSS does..   You are putting a lot of faith in the vehicles onboard system and evse playing fair with each other.    or contactors not to get stuck, etc.    

@Pir8radio The plug does not really matter, NACS (Tesla) or SAE J1772 with a Tesla adapter. They are electronically and pin equivalent. Tesla seems to have it figured out, every Tesla vehicle shipped in North America uses the same pins for AC charging via NACS and J1772 or DC supercharging.


I would assume non-Tesla OEMS would have to comply with the same standards for their onboard charging systems to use Tesla Supercharger network and NACS socket.


I have been using a Tesla plug on my personal station since 2012 without issue.

Yes, but what I’m saying is since the plug uses the same two current carrying pins for AC as they do for DC there’s a potential for that system inside the vehicle or charger to malfunction. Just as you don’t recommend solid-state relays inside and EVSE similar safety issues can occur with that plug. For example the contactor for the internal ac charger gets stuck and then you plug it into a dc system. Now your ac and dc systems are tied together. It’s not good practice from an engineering stance to reuse those same pins for ac and dc IMO. Yeah we haven’t seen issues yet but airbags are a relatively new safety requirement as well as vehicles originally didn’t come with seatbelts. I can see sharing of AC and DC being not allowed in the future once we have a couple accidents.

@pir8radio Are you saying Teslas should not charge on AC charging stations? 


Tesla has been using the same pins for AC/DC charging since The Model S was released in 2012, we are not aware of any issues with DC from the vehicle damaging AC charging stations. 10 years and 4.5 million vehicles would seem to be a pretty large sample size.


We are not experts on the Tesla DC system but, we are aware that there are physical contactors in both the vehicle and battery. If the vehicle system is anything like the charging stations, then a DC fault would force the vehicle to open the vehicle and/or the battery contactor. I would be shocked if Tesla did not think this one through.

Hi OpenEVSE Support, you mentioned “Tesla cables sacrificed from a Tesla Mobile Connector or HPWC work perfectly on OpenEVSE.” I have a 48Amp openEVSE can I use mobile connector cables at 48amp? Just wondering since mobile connector is max 32 amp.

NACS level 2 is electrically identical to J1772. People today use OpenEVSE units with NACS / Tesla cables without issue.


*however*, as NACS was proprietary, few to no NACS cables / handle vendors exist today. (check yourself, you can find tons of vendors selling J1772 components, but almost zero Tesla / NACS cables / handles / etc.)


As soon as 3rd party components become a thing, I'm sure OpenEVSE should be able to support native NACS cables.

Electric Ant, Make sure the wires leading from the control board to the connector are the correct gauge for the amperage.

I opened a ticket with the OpenEVSE team, I'm working with a team in Ohio who is interested in developing a NACS connector, support from OpenEVSE would be helpful.

@OpenEVSE Support


Looking over the NACS aka J3400 interface info I found that vehicles do not have contactors on the onboard AC charger, they tie the input directly to the L1/L2 DC pins on that connector..  So when you are charging via DC you are actually pumping DC into the AC input on the onboard AC-DC charger.   They recommend the onboard charger be designed to withstand this but admit a malfunction of the EVSE could damage that onboard charger.   I would also think this could lead to a safety issue (depending on who designs the onboard charger) allowing HV DC to leak to the vehicle body via the case of the AC-DC charger.    Where as AC would be GFCI tripped DC wouldn't.  This is all I was saying above, and looks like it is possible even if not reported yet.   Here is the clip below, and here is the link to the interface specs for you, may be handy for future EVSE firmware stuff I don't know..  :-)  

3.1 On-Board Charger DC Voltage Withstand Tesla’s implementation has the AC input of the on-board charger directly connected to the fast charge link. With this implementation, DC high voltage will be applied to the AC input of the on-board charger whenever DC fast charging is active. The on-board charger must be designed to withstand this DC voltage and must not attempt to convert power when DC fast charging is active to avoid damage to the on-board charger power converters. The maximum DC voltage that the on-board charger must withstand can be derived as the greater of maximum pack voltage and maximum voltage seen during the DC charging external isolation check If the on-board charger cannot meet this voltage withstand requirement, an alternative option is to separate the on-board charger from the fast charge link using relays or contactors. Failure modes of DC EVSEs must also be considered when choosing the maximum withstand voltage. Tesla has encountered situations where DC EVSEs applied higher than expected DC voltage during external isolation testing, caused either by vehicle or EVSE malfunctions, resulting in damage to the on-board charger or other components connected to the fast charge link. An example of this is EVSEs rated for maximum voltage supported by the CCS standard unexpectedly applying this maximum voltage to a vehicle advertising it does not support this range. While it is not required to ensure there is no damage to components due to this failure mode, manufacturers should consider this malfunction when designing the system and at minimum ensure the failure is contained and does not pose safety hazards.

another thing I was thinking, with the J3400, aka NACS, the tesla version uses CAN bus to relay info from the car to the supercharger so the network knows who's Credit card to charge (that you have on file with tesla).   CAN traffic isn't encrypted, so all someone would have to do is stand up a few "free" chargers and skim the users info from the car CAN bus traffic or create a handheld simulated EVSE so the tesla gives up that info, then emulate it on a reprogrammable converter cable (small extension) man in the middle, then one could emulate the recorded vin or whatever data is sent via the can bus to the supercharger and basically perform credit card fraud by stealing free supercharging.      Elon jumps into things too quickly without planning for the long term future. I do like the connector, but some things need to be fixed or cleaned up in the standard first.   I wouldn't use the unencrypted can traffic to handle user tracking especially since it effects a users wallet. 

Are you sure that’s how billing happens? I read that the car sends billing info via the car’s cellular modem which is encrypted. Only vin number is sent to supercharger. 

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