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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.

Just opening the discussion. :-)

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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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My understanding is the communication expresses the vehicle ID, not the credit card information. The value of skimming information would only come if someone wanted to then replicate the vehicle ID to charge their own car. I can't imagine a pirate going so far just to steal a charge every now and then but this is a fair point.

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Most of your posts do not have to be approved. I see 2 in the bucket now, not sure why. One was yours from a few days ago and the other Electric Ant.

We do not have any source for NACS (SAE J3400) yet. We have been working with Phoenix Contact and ITT to get some, but they are not selling anything yet.

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. 

@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.

yea that post i just did about the tesla extensions said it needed approval too, as will this one..  every post i have made for quite a while needs approval.. I assumed it was like that for everyone on the forum.  lol   i usually have to wait a few days before i see my posts due to someone approving..    odd....

yea i have not had luck other than used stuff.     I did reach out to a few people that make tesla extension cables, they are getting the ends from somewhere.     one looks custom, i asked them if they would sell to me,   maybe they would sell to you for volume.   

Lectron makes one, and this place looks like they are having custom ends made?         

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.

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.


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


(From the standard at

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