USB-C uses two pins for power delivery, but the cable and charger determine how much current flows

A USB-C connector has 24 pins total, but only two of them carry the actual power that charges your device: pin 4 and pin 9. These are the VBUS (voltage bus) pins. The other 22 pins handle data, ground connections, configuration, and communication between your charger and device. When you plug in a USB-C cable, power flows through pins 4 and 9 simultaneously, and the voltage and current depend on what your charger supports and what your device requests.

The reason USB-C has two power pins instead of one is redundancy and balance. Using two pins spreads the electrical load, which reduces heat and allows for higher power delivery without overheating the connector. A single pin would be a bottleneck. The connector is also reversible — you can plug it in either way — so having power pins on both sides of the connector layout ensures power reaches your device no matter which orientation you use.

Key Takeaways

  • Pins 4 and 9 are the VBUS pins that deliver power; all other pins handle data, ground, or communication.
  • Your charger's wattage and your device's power needs determine the voltage and current flowing through those two pins, not the pins themselves.
  • USB Power Delivery (USB PD) is a protocol that lets your charger and device negotiate the right power level, and it uses separate pins to communicate that negotiation.
  • A damaged pin 4 or pin 9 will prevent charging even if the cable and charger are fine, because power cannot reach your device.

How the two power pins work together

Pins 4 and 9 are physically identical and carry the same voltage at the same time. They are not one pin doing half the work — they are two pins doing the same job in parallel. This design means the connector can handle higher current without the pins themselves overheating. A standard USB-A port, by contrast, has only one power pin (pin 1), which is why USB-A chargers are limited to lower wattages.

The voltage on pins 4 and 9 is typically 5 volts for basic charging, but with USB Power Delivery it can be 9V, 15V, 20V, or even higher depending on the charger and device. The current (measured in amps) also varies. A basic 5W charger might deliver 1 amp, while a 100W charger delivers up to 5 amps. The two pins split that current between them, so each pin carries roughly half the load.

What the other 22 pins do

The remaining pins handle everything except raw power delivery. Pins 1, 6, 11, and 16 are ground pins that complete the electrical circuit. Without a good ground connection, power cannot flow. Pins 2, 3, 10, and 15 are for high-speed data — USB 3.1 or Thunderbolt signals. Pins 5 and 12 are CC (configuration channel) pins that let your charger and device communicate about power levels, cable orientation, and whether the connection is safe.

The CC pins are critical for USB Power Delivery. When you plug in a USB-C cable, your device pulls a small signal on one of the CC pins to tell the charger "I'm here." The charger responds by sending back information about what power levels it can provide. Your device then requests the voltage and current it needs. This entire negotiation happens on the CC pins before any significant power flows through pins 4 and 9. If a CC pin is damaged, your device may not charge at all, or it may charge at only 5W even if you have a powerful charger.

Why you might have charging problems even with good pins

A broken pin 4 or pin 9 will stop charging completely, but most charging failures happen elsewhere. A damaged CC pin prevents negotiation, so your device charges slowly or not at all. A bad ground pin (1, 6, 11, or 16) breaks the circuit. A frayed or pinched cable can damage any pin, but the power pins are the most robust because they are thicker than data pins.

Charger quality also matters. A charger that does not properly support USB Power Delivery may only send 5V even if your device can accept 20V. Your device will charge, but slowly. Conversely, a device that does not negotiate properly might not request the higher voltage it needs, so it charges at 5V even though a capable charger is connected. The pins themselves are fine — the communication between charger and device is the problem.

How to tell if a pin is damaged

If your device charges with one charger but not another, the pins are probably fine — the issue is charger compatibility or power delivery negotiation. If your device does not charge with any charger, try a different cable first. A cable failure is far more common than a port failure, and a bad cable can damage the pins in your device's port over time.

If a different cable does not help, look inside the USB-C port with a flashlight. The pins should be straight and evenly spaced. Bent, corroded, or missing pins mean the port is damaged. Pins 4 and 9 are the thickest and are located on the outer edges of the connector, so they are usually the last to break. If you see visible damage to the outer pins, the port needs professional repair or replacement.

USB Power Delivery and pin voltage

USB Power Delivery (USB PD) is a standard that lets chargers and devices negotiate higher voltages and currents than the basic 5V limit. A USB PD charger can send 9V, 15V, or 20V through pins 4 and 9, and your device requests the voltage it needs through the CC pins. This is why a 100W USB-C charger can charge a laptop, a phone, and a tablet — each device requests the right power level for its battery.

The pins themselves do not care about the voltage. Pins 4 and 9 are rated to handle up to 20V and 5 amps, which is 100 watts. Higher-power cables (like those for 240W charging) use thicker pins and are physically larger, but the pin numbers and function remain the same. Your charger and device handle the voltage negotiation; the pins just carry whatever voltage they agree on.

Frequently Asked Questions

Can I charge my device if one of the power pins is slightly bent?

Probably yes, at least for now. A slightly bent pin 4 or 9 may still make contact, though the connection might be loose or intermittent. You may notice slow charging or the connection dropping and reconnecting. A bent pin will likely get worse over time and eventually break, so have the port inspected or replaced before it fails completely.

Why does my phone charge slowly with some chargers but not others?

Your phone and charger negotiate the right power level through the CC pins. If the charger does not support USB Power Delivery, or if the cable is not certified for high power, your phone may only receive 5V instead of the 9V or 20V it can handle. Try a different cable or charger to see if the speed improves. The port pins are probably fine.

What happens if pins 4 and 9 are damaged but the other pins work?

Your device will not charge at all, because power cannot reach the battery. Data transfer through the other pins might still work, so your computer could recognize your device, but charging requires pins 4 and 9 specifically. The port needs repair.

Do I need a special cable to use USB Power Delivery?

Not a special cable, but a certified one. Any USB-C cable can carry USB PD signals, but the cable must be rated for the power level you want. A basic cable rated for 5A can handle up to 100W. Cables rated for 240W are thicker and more expensive, but the pins and connectors work the same way. Check the cable packaging or your charger manual to confirm compatibility.

Can a damaged CC pin prevent charging even if pins 4 and 9 are fine?

Yes. If a CC pin is damaged, your device and charger cannot communicate about power levels. Your device may not recognize that a charger is connected, or it may charge at only 5W as a safety default. The power pins are intact, but the negotiation fails, so charging is slow or does not happen at all.