The 500 A problem
Power is volts times amps. That is the whole article, but the consequences are worth spelling out, because they are the single most common source of disappointment at a fast charger.
A cabinet has two ceilings, not one. It has the power rating painted on the side, and it has a current limit set by the cable, the connector pins and the power electronics. Most high-power CCS cabinets stop at 500 A. That number does not appear on the sign.
The arithmetic
A 400 V-class pack is not at 400 V. It sits somewhere around 345 V when nearly empty and 390 V when nearly full. Multiply:
345 V x 500 A = 172 kW
390 V x 500 A = 195 kWSo a 400 V car on a 500 A cabinet is physically capped somewhere around 173 to 195 kW, no matter what the cabinet is rated for. A Tesla Model 3 Long Range has a curve that peaks at 250 kW. It never sees it on that hardware. It peaks at 180 kW and the cabinet is not even trying hard.
What this does to the price list
Here is the same car, the same 10 to 80% session, on four cabinets whose stickers differ by 100 kW:
| Plug | Peak reached | 10 to 80% |
|---|---|---|
| 250 kW | 180 kW | 24 min |
| 260 kW | 180 kW | 24 min |
| 320 kW | 180 kW | 24 min |
| 350 kW | 180 kW | 24 min |
Four price tiers, one result. They are all 500 A units, and 500 A is 500 A. If you are choosing between a 250 and a 350 kW stall in a 400 V car, you are choosing between two identical experiences.
The way out is voltage, not amps
An 800 V pack draws the same power at half the current. At 700 V, 500 A is 350 kW, so an 800 V car can use the whole cabinet:
700 V x 500 A = 350 kWThat is the entire argument for 800 V architecture. It is not that the cells are better. It is that the cable between the cabinet and the car has a fixed current limit, and doubling the voltage doubles the power you can push through it. Every 800 V car on this site keeps gaining as the plug rating rises, right up until its own curve becomes the limit. Every 400 V car flattens at 500 A and stops caring.
Where to see it
Open the calculator, pick a Model 3 and a 350 kW plug, and read the callout under the main chart. Then switch to an Ioniq 5 without touching anything else. Same cabinet, same session window, 80 kW more power and seven minutes less time, entirely because of pack voltage.
There is one more twist, which is that Tesla built its cabinets the other way round: around 700 A at only 500 V. That is Supercharger reality.
Next
Supercharger reality: 700 A at 500 V
Tesla went high-current and low-voltage, which is why a 400 V Tesla really does see 250 kW, and why an 800 V car plugged into one has to split its pack.