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Difficulty: MediumLaptop Power Systems and Battery Management

A technician is troubleshooting a executive's laptop that powers off instantly whenever the AC power adapter is disconnected. When plugged into the wall outlet, the operating system indicates the battery status as '100% Fully Charged'. However, pulling the power plug causes immediate system shutdown without any low-battery warnings. Which of the following is the most likely cause of this issue?

  1. The laptop battery cells or integrated Battery Management System (BMS) have failed and can no longer supply power under load.Answer
  2. B
    The Lithium-ion battery requires a complete manual deep discharge cycle down to zero percent to re-calibrate its internal charge threshold sensors.
  3. C
    The laptop's USB Type-C charging port has lost DisplayPort Alt Mode signaling negotiation with the AC power supply.
  4. D
    The system memory has been installed in mismatched SO-DIMM slots, forcing the power management controller to shut down on battery.

Answer

The laptop battery cells or integrated Battery Management System (BMS) have failed and can no longer supply power under load.
When a laptop functions properly on AC power but instantly loses power upon AC disconnection despite displaying a full charge, the battery has lost its ability to hold a charge or output power under load. A failure in the battery cells or internal Battery Management System (BMS) prevents current flow, necessitating battery replacement.

Step-by-Step Solution

1
Analyze the reported power symptoms
The laptop operates normally on AC power and reports a full charge, but shuts down immediately when AC power is removed.
This indicates that the AC power supply and DC jack are functioning, but the battery cannot output electrical current to sustain system operation.
2
Evaluate battery health vs status indication
A faulty battery or failed BMS circuit can report full voltage/charge to the OS while connected to AC power, but collapse under the actual load of the system.
Lithium-ion batteries age over time and can suffer internal cell degradation or open internal thermal fuses, leading to total capacity loss.
3
Determine the necessary technician action
The internal battery pack must be replaced.
Replacing the failed battery unit restores DC power delivery and battery runtime.

Key Concept

Laptop Battery Failure Symptoms and Power Delivery
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Topics

Laptop Power Systems and Battery Management

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