Plug Design for Tesla NACS

In this series of articles, we will briefly analyze the changes in the structure design of Tesla’s charging port, mainly selecting the charging stand adapted to Model S/X in 2015 and the cable version adapted to Model 3 in 2018 for brief analysis. The aluminum tube charging base assembly is not disclosed. For other information on the aluminum tube version, please see the previous article: Tesla—charging busbar patent; unique and constantly evolving.
This article lets us go back to 2015 and briefly analyze the structural design of the early Tesla charging interface based on the Model X of that era. Use it as a starting point.

The following analysis and pictures containing text do not represent the final mass production status of the technologies mentioned below. It does not represent any universal or accidental situation of the technology mentioned below, it is only a simple analysis and discussion.

Tesla NACS plug structure

Overall socket & power design
Features of the first version of the Tesla NACS interface SOP include:
● Ultrasonic welding connection wires and terminals meet its V2 charging requirements for the first time (subsequent iterations will reach close to V3 level);
● 90° outlet & screw lock terminal;
● Removable protective cover (with anti-accidental removal);
● Colorful aperture and light source visual design;
● The ground wire has a small cross-sectional area & AC and DC share the same interface;
● Signal + PE plug-in and socket can be separated;
At the same time, functions such as charging the vehicle, pulling out the gun, and opening the lid were also cutting-edge designs at the time.
Vehicle layout position (Model X)
The overall panel size is smaller than CCS & GB AC and DC integrated. For details on the size of the plug-in part and the charging logic, see the previous article: Some data on Tesla overcharging.
Charging socket assembly details (Model X)
The biggest feature of the first version of SOP is similar to the current aluminum pipe. The protection of the outlet position does not rely on the charging base itself. The removable protective cover at the tail + 90° outlet to increase the convenience of wire harness assembly and maintenance is still retained today, and row/rod/tube conductor products are becoming more and more popular now. There are more and more BMK manufacturers.
Details of charging socket assembly opening cover
In addition, due to the overall design requirements, the signal + PE plug-in is integrated with soft and hard glue + wire + terminal. At the same time, after the buckle is assembled into the socket, the removable protective cover can be used to achieve functions similar to CPA, which is also worth learning. There is some shaking after the one-piece molded part is fully assembled.
Charging socket assembly external interface and signal details
In terms of power design, in the early stage, tinned copper + crimping technology was used to achieve low-power charging (compared to the current maximum power of high-power charging). Later, pure copper + ultrasonic welding and aluminum wire + ultrasonic welding were used, but what has not changed is the protective design of the terminals and cables mentioned above. While the wires are constantly being upgraded, the protection has not been upgraded. Looking at the past and now, is it necessary to explore the protection-free termination design on aluminum conductors? Such as sol-gel coating.

Ultrasonic welding of charging socket assembly:
In terms of shielding treatment, due to some reasons, Model X and S respectively choose the socket end shielding heat shrink tube to wrap the single-end suspension and the shield crimping and then connect the body sheet metal to the double-end grounding. There is also a similar cross-selection situation between the subsequent 2018 Model 3 and the current aluminum tube solution. The subsequent implementation of shielding effectiveness under higher charging power deserves further study.

Charging socket assembly shielding treatment:
In terms of performance, thanks to ultrasonic welding and low terminal resistance, current analog charging can maintain full power current carrying for a long time in an air-cooled environment.
The grounding design is as before, the conductor cross-sectional area is smaller than most DC interface designs, which greatly reduces the space occupied by the charging interface, and the grounding is designed for the car charger.
Charging socket assembly grounding aperture and others:
Colorful aperture + uniform gradient color, this is also a relatively excellent sensory experience at present. The overall design is centered on the tail pin limiting plate. Two layers of translucent plastic parts project the light source on the PCBA to the light-transmitting position of the charging port, achieving uniform light distribution in the forward viewing area.
In other examples of different interfaces at the same time, different aperture design positions are achieved by changing the position of translucent plastic. This is also the advantage of standardized aperture design.

Charging socket assembly aperture visualization
But the light assembly is built into the charging socket. There are areas that need constant adjustment in the entire socket manufacturing and vehicle matching of new models (perhaps cost is also one of the key points). In subsequent Model 3/Y models, the lighting module in the charging socket assembly is moved out of the socket body and placed in the socket connection plate, often with the Tesla LOGO.

Partial PCBA and Pin of charging socket assembly
Compared with GB IEC and other AC and DC integrated solutions. The first version of Tesla NACS SOP signal and ground output uses 6Pin plug-in (1Pin reserved) * 1 + Pilot * 1 + ground terminal * 1 + Prox * 1 (PE is integrated with Pilot and Prox). The overall simplified low-voltage loop output reduces the number of wire harness assemblies and reserves space for subsequent PCBA and panel miniaturization. Subsequent requirements for temperature monitoring and other aspects will continue to increase. Tesla’s latest NACS is 12+3Pin (including plug-in locking lock, except for some Model Gun lock), CCS is 12+3 Pin (including gun lock).

Tesla NACS outlet details

Current standard charging socket assemblies
Regarding the arrangement of the locking lock of the insertion gun, NACS has been at the bottom of the socket since the first version of the SOP to the current version, and the drainage is arranged together. It is good for drainage, but the ability of the entire lance lock to resist the intrusion of debris is weaker than other standard interfaces (it occasionally fails here). At present, the aluminum tube solutions of most vehicle models abandon the first version of the SOP lock design and adopt solutions with a better protection level.

The mounting plate screws are all self-tapping screws, 4 in total.

Charging socket assembly secondary BOM failure mode
Early versions always have a lot of failure modes. Some failure modes have been circumvented, and some failure modes currently persist. The following is a brief analysis of a structural design failure.
Failure mode: Anti-touch cap falls off. This failure mode occurs when the terminal is turned. Due to the special nature of the subsequent punching and rounding processes, the risk of falling off is greater than before. In addition to Tesla, other OEMs have also experienced similar problems.

Charging socket assembly failure mode
To minimize the risk of failure, during the early stage of refined dimensional design and multi-dimensional verification, changing the anti-touch finger and terminal connection methods can also be taken into consideration.