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Difficulty: HardLaptop Power Systems and Battery Management

A technician is troubleshooting a laptop that exhibits battery drain and displays a 'Slow Charger' warning when connected to a 100W universal USB-C Power Delivery (USB-PD) docking station. Plugging the docking station into the laptop's left USB-C port allows full-speed charging, but plugging the same cable into the right USB-C port causes the laptop to discharge under heavy workloads. Which of the following is the MOST likely cause of this behavior?

  1. The right-side USB-C port supports data transfer only and lacks power input capability through the internal power management controller.Answer
  2. B
    The right-side port requires a software driver update to convert its DisplayPort Alt Mode protocol into high-wattage Power Delivery negotiation.
  3. C
    The smart Lithium-ion battery management circuit requires a complete 0% deep discharge cycle to recalibrate power routing for the secondary port.
  4. D
    The internal DC-in power jack assembly has failed and requires immediate component replacement.

Answer

The right-side USB-C port supports data transfer only and lacks power input capability through the internal power management controller.
Modern laptop designs frequently feature asymmetrical USB-C port specifications. While all ports use the identical USB Type-C connector shape, only specific ports are connected to the internal power management controller with USB Power Delivery (USB-PD) sink capabilities. Connecting a high-wattage charger to a data-only or low-power output USB-C port will result in low-power warnings and battery drain under load because the port cannot negotiate high voltage/current profiles.

Step-by-Step Solution

1
Analyze the reported symptoms across both ports
The left USB-C port charges normally at full 100W power, while the right USB-C port prompts a 'Slow Charger' warning and allows battery discharge under load.
Different behavior using the exact same AC adapter and dock isolates the issue to port-specific capabilities on the laptop motherboard rather than the external power supply or battery itself.
2
Evaluate laptop USB Type-C hardware design standards
Identify that manufacturers frequently configure specific physical USB-C ports with dedicated USB Power Delivery (USB-PD) integrated circuits for charging input, while secondary USB-C ports may only support USB 3.x data streams or standard 5V/15W downstream device power.
Physical connector uniformity (USB-C) does not guarantee feature parity across all ports on a given device.
3
Select the correct diagnostic conclusion
Confirm that the right-side port lacks the required motherboard routing to accept high-wattage power input.
Plugging into the designated charging port resolves the symptom without unnecessary hardware replacement or misdirected software troubleshooting.

Key Concept

USB-C Power Delivery (USB-PD) and Motherboard Port Feature Asymmetry
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Topics

Laptop Power Systems and Battery Management

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