Tesla's NACS Charging Plug

NOTE: I don't own a Tesla, I own two EV's a Hyundai Kona EV, and a Kia Niro EV. Both have CCS plugs which are bulky, hard to plug in, and generally terrible.

EV charging comes in several flavors, but the bottom line is you either plug into an AC outlet or a DC outlet. An EV 'charger' is not really a charger like you would have for an iPhone or laptop. When charging an EV the box is simply a control/communication devices and a relay. To simplify the idea, when you plug into either type the vehicle communicates with the control box, and they agree on how the connection will be made and how much current will be allowed on the connection. In the case of an AC connection the actual charger is on the vehicle, and it converts the AC to DC allowing current flow up to the negotiated rate, sending DC to the batteries. In the case of a DC connection the vehicle bypasses the on-board charger dumping the high-voltage dc directly to the battery pack.

AC charging pretty much standardized on the J-1772. Early DC charging like on the Nissan LEAF used two different plugs the 'J-1772' for AC charging, and 'CHADEMO' for DC (still widely used in the far east). Tesla built it's plug as dual use allowing the charging conductors to use either AC or DC to start with. The current CCS decided they would maintain compatibility by using the J1772 connector and adding two overlarge connectors on the bottom for the DC creating a plug with about a 3-odd inch bulky irregular footprint. As someone who had to stand out in the ice and snow in a Wal-Mart parking lot trying to stuff that thing in the car for a charge, I can tell you I cursed that design. Bad enough on a warm day traveling thru Texas, abysmal in snow along I-40 in New Mexico. Current CCS standards include liquid cooling the cables, one of those 'seemed like a good idea at the time' things, that make the cables very stiff and awkward to get plugged in.

The engineering problems start to manifest as the charging current goes up. The higher the current the thicker the wire in the cables needs to be to handle the load without getting hot. Increasing voltage, decreases current. Higher voltages mean better insulation, much easier and less expensive than more metal in a wire. Over time engineers have upped the voltages on the batteries so newer EV's batteries are running up in the 800v range, which allow for faster charging without needing cables the size of your arm to handle the current. If you want to charge at 300KW you need to push a little under 400 amps at 800 volts. If you were using standard wire that would be 500KCMIL at 75c. That's bigger around than your thumb. The rules get a little different over short runs, and you can bring the gauge down as the temperature capability goes up. I have no idea how they are doing this with the cable they are using now.

Since Tesla opened up it's charging plug specification last year I was hopeful it would get wide adoption. The WSJ article 'Tesla Has Won the EV Charger Wars' - Mon June 12, 2023, seems to indicate it would be expensive to shift CCS infrastructure to the 'Tesla Standard'. I beg to differ. This would require swapping out, or simply adding a couple hundred dollars worth of electronics and cabling on a device that starts at $25K and goes up. There are already adapters that cost $200-300 dollars that convert the CCS plug to a Tesla plug and myriad Tesla's are already charging at many of the CCS based DC stations using this adapter. Unlike a gas pump with different plumbing for each type of fuel, a charging station is basically a big giant transformer and rectifier. Once you have engineered getting high voltage DC, the rest of it is just a small cheap programmable electronic control that allows the car to communicate with the station and allow the proper voltage/current down to the plug. The plug itself is not really that significant, and I'll guarantee the independent charging network equipment providers have already got working tesla style prototypes. If you are investing that kind of money you want to offer service to the widest audience possible.

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blog/tesla_charging_plug.txt · Last modified: 2023-06-12 14:20 by ksadmin
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