Why Doesn’t My Powerbank Deliver 100% of Its Capacity?

It’s normal for any powerbank to deliver slightly less usable energy to a device than the total energy stored inside the battery.

When a powerbank charges a device, energy is converted and regulated to match your device’s requirements. During this process, a small amount of energy is naturally lost as heat and system overhead. This is standard across all powerbanks and charging systems.

Why energy loss occurs

When charging a device:

• Voltage is adjusted to match your device’s needs

• Some energy is lost as heat during conversion

• Cable resistance and internal electronics use a small amount of power

• Wireless charging creates additional heat and reduces efficiency

Because of this, the usable output is always lower than the total stored energy.

For Flash Pro and Flash Pro Plus, typical efficiency when charging laptops and high-voltage devices is around 70%.

Wireless charging operates at lower efficiency due to heat generation.

How to Estimate Charging Performance

You can estimate real-world charging performance using this simple guide:

Powerbank energy (Wh) × ~70% ÷ device battery size (Wh)

This provides a realistic expectation when charging larger devices like laptops.

Example Estimates

💻 15" MacBook Pro

Battery: 83.6Wh
Estimated charge: ≈ 79%

💻 16" MacBook Pro

Battery: 99.8Wh
Estimated charge: ≈ 64%

📱 iPad Pro 11"

Battery: 29.37Wh
Estimated charge: ≈ 2+ full charges

Tips to maximise efficiency

• Use high-quality USB-C cables

• Use wired charging when possible

• Avoid heavy device use while charging

• Keep devices cool during charging

Good to know

• This energy conversion is normal for all powerbanks

• Wireless charging is less efficient than wired charging

• Larger devices require more energy and will receive fewer full charges

If you’d like help estimating performance for a specific device, please submit a request and our Customer Happiness Team will be happy to assist.