How to Charge Your Laptop from a USB External Battery

Charging your laptop from a USB external battery, also known as a power bank, can be a convenient and cost-effective solution, especially when you’re on the go. To ensure a safe and efficient charging process, you need to consider several technical factors, including the capacity, output voltage, and charging time of the power bank, as well as the input voltage of your laptop’s charger.

Understanding Power Bank Specifications

When selecting a power bank to charge your laptop, you should pay close attention to the following specifications:


The capacity of the power bank should be higher than the battery capacity of your laptop. For example, if your laptop has a 40Wh battery, you should choose a power bank with a capacity of at least 40Wh. However, it’s important to note that power banks are typically rated with an assumption that the nominal voltage is 3.7V. This means that a 25,000mAh power bank would have an actual capacity of around 92.5Wh.

Output Voltage

The output voltage of the power bank should match the input voltage of your laptop’s charger. Using a power bank with the wrong voltage can damage your laptop’s battery or even cause a fire. For instance, if your laptop charger has an input voltage of 19.5V, you should choose a power bank with an output voltage of at least 19.5V.

Output Current

The output current of the power bank should be at least 2A for fast charging. Many laptops require a higher current to charge efficiently, so a power bank with a higher output current (e.g., 3A or 5A) would be ideal.


The wattage of the power bank should be at least 45W for most laptops. This ensures that the power bank can provide enough power to charge your laptop effectively. Some high-capacity power banks can deliver up to 100W or more, which can charge laptops even faster.


The power bank should have a USB-C or USB-A connector that matches the charging port on your laptop. Make sure to use the appropriate cable to connect the power bank to your laptop.

Charging Your Laptop with a Power Bank

how to charge your laptop from a usb external battery

To charge your laptop from a USB external battery, follow these steps:

  1. Choose the Right Power Bank: Select a power bank that meets the technical specifications mentioned above, ensuring that it has a higher capacity and matching output voltage compared to your laptop’s battery and charger.

  2. Connect the Power Bank: Use the appropriate USB cable (USB-C or USB-A) to connect the power bank to your laptop’s charging port.

  3. Turn on the Power Bank: Press the button on the power bank to start the charging process.

  4. Monitor the Charging Process: Keep an eye on the charging progress to ensure that the power bank does not overheat or overcharge your laptop. Some power banks have built-in safety features to prevent these issues.

  5. Disconnect the Power Bank: Once your laptop is fully charged, disconnect the power bank to avoid any potential issues.

Factors Affecting Charging Time

The charging time for your laptop using a power bank can vary depending on several factors:

  • Power Bank Wattage: Higher-wattage power banks (e.g., 45W or 60W) can charge laptops faster than lower-wattage models.
  • Laptop Battery Capacity: Laptops with larger battery capacities will take longer to charge than those with smaller batteries.
  • Laptop Power Consumption: If your laptop is performing resource-intensive tasks while charging, it will take longer to reach a full charge.

As a general rule, a high-capacity power bank (e.g., 25,000mAh or more) with a high wattage (45W or more) can charge most laptops in 2-3 hours, while a lower-capacity or lower-wattage power bank may take 12 hours or more to fully charge your laptop.

Benefits of Charging Laptops with Power Banks

Charging your laptop with a USB external battery offers several benefits:

  1. Convenience: Power banks are lightweight and compact, making them easy to carry around and use on the go, unlike bulky laptop chargers.
  2. Cost-Effectiveness: Power banks are generally more affordable than purchasing a replacement laptop charger, especially if you need to charge your laptop in multiple locations.
  3. Portability: With a power bank, you can charge your laptop anywhere, even in places where traditional power outlets are not available, such as during outdoor activities or while traveling.

By understanding the technical specifications and following the proper steps, you can effectively charge your laptop using a USB external battery, ensuring a safe and efficient charging process.