02-06-2025
Did Megawatt DC Fast Charging for EVs Just Inch Closer to Reality?
Cars are already on sale in China that purport to support 1-megawatt charging speeds (as in, 1,000 kW), well in advance of any widespread roll-out of DC fast-charging infrastructure capable of supporting such lofty charging speeds. (Today, 350-kW chargers are the fastest units commonly found in America.) Fortunately for Americans hoping to remain in the EV-technology race with China, Tesla's original North American Charging Standard (which wasn't then, but now kind of is a "standard") was designed and developed to support such high rates of charging power.
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'The publication of SAE J3400/2 as an SAE International standard represents our confidence in the maturity of the 1,000-volt-capable NACS coupler for reliable and safe bidirectional power transfer,' said Dr. Rodney McGee, Ph.D., P.E., chairman, SAE J3400 NACS Task Force, and Research Engineer at the Transportation Electrification Center at the University of Delaware, whom MotorTrend often consults on charging matters.
What SAE J3400/2 Does
The new standard defines the physical architectural and mechanical specifications of the EV connector and vehicle charge port, to make safer and faster electric vehicle charging possible across the continent. SAE J3400/2 standardizes the physical architecture of both the connectors and charge ports, providing both 2D mechanical drawings and 3D models, so that OEM and charging equipment engineers have the critical specifications needed to develop interoperable hardware.
Does it Look Different?
Well, yes and no. In order to support the higher voltage and power flow, there needed to be a bit more space between the positive and negative terminals to allow for "creepage and clearance. The physical arrangement is the same and cars built to the 500-volt standard will work with the 1,000-volt plug (at lower power). The Cybertruck was the first 1,000-volt-capable Tesla model, so J3400/2 charge port will largely look similar to the Cybertruck's.
Ensured Compatibility
The standard also defines geometric clearances in the transition from the charger handle to the actual connector and the environment surrounding the charge port to ensure that vendors don't develop chargers that interfere with the the port (as happened with many CCS-to-NACS adapters that required removal of wheel-arch molding trim to plug into a Cybertruck).
The SAE J3400 Family of Standards
J3400/2 completes a family of standard documents that started with the J3400, which defined the North American Charging System (NACS) for Electric Vehicles, spelling out general requirements for NACS including AC and DC power transfer rates, interoperability, security and communications protocols (including vehicle to infrastructure). SAE J3400/1 then spelled out the physical, electrical, and performance requirements as they applied to adapters for connecting CCS (or other) chargers to NACS.
What 1-MW Charging Might Look Like
In China, BYD's Super e-Platform supports 1,000-volt charging at 1,000 amps, which supports 10C charging in its cars. That means it charges at 10 times the battery's rated capacity. This allows it to add 250 miles of range in 5 minutes. The jury is still out on the long-term effects on battery health of frequent charging at these lofty rates, however, and it's likely that certain battery chemistries (existing and under development) may tolerate ultra-fast charging better than others (the greatest hope is for solid state batteries to tolerate it well).
