CompTIA A+ Core 1 (220-1201)Mobile DevicesMedium
A technician connects a laptop to a USB-C docking station. The laptop requires 65W to charge normally, but the dock's USB-C Power Delivery port only supports pass-through charging up to 60W. What is the most likely result when the laptop is docked, powered on, and actively being used?
- AThe dock will automatically negotiate extra wattage to reach 65W
- BThe laptop may charge slowly or the battery may slowly drain because the dock cannot supply enough wattage under load
- CThe laptop will charge at full speed with no issues
- DThe laptop's battery will be permanently damaged from overcharging
Show answer & explanationAnswer & explanation
Correct answer: B. The laptop may charge slowly or the battery may slowly drain because the dock cannot supply enough wattage under load
Since 60W is less than the 65W the laptop requires, the dock cannot fully meet the laptop's power demand, especially under active use (CPU/GPU load). The laptop will draw from the battery to make up the difference, resulting in slow charging or gradual battery drain rather than fast or full charging.
Why the other options are wrong
- A. USB-C PD negotiates within the connected charger's fixed capability; a 60W port cannot exceed its rated output.
- C. 60W supplied is less than the 65W required, so full-speed charging is unlikely under load.
- D. Undercharging does not cause overcharging damage; the risk here is insufficient power, not excess.
USB-C Power Delivery Wattage Mismatch
When a charging source (like a dock) supplies less wattage than a device requires, the device may charge slowly or drain its battery under load rather than being damaged.
- USB-C PD negotiates the highest wattage the charger can supply, up to its max rating
- If device power draw exceeds supply, battery makes up the difference
- Common issue: 60W dock cannot fully power a 65W-required laptop under heavy use
Memory trick: '60 can't cover 65 — battery picks up the slack'