When shopping for a power bank, you’ve likely encountered specifications like mAh (milliamp-hours) and Wh (watt-hours). At first glance, these terms might seem like confusing technical jargon, but they’re crucial for understanding how much energy a power bank can store and deliver. 

In this guide, we’ll explore what mAh and Wh mean, how to convert mAh to watt-hour and convert watt-hours to mAh, and why these conversions are essential for choosing the right power bank.

In this article:

• What’s the Difference Between mAh and Wh
• How to Convert mAh to Watt-Hours
• How to Convert Watt-Hours to mAh
• Voltage, Amps, and Charging Power
• How Many Times Can a Power Bank Charge Your Phone
• Wrapping It Up
• Frequently Asked Questions

Let’s get started!

What’s the Difference Between mAh and Wh?

Before diving into how to convert mAh to watt-hour and the reverse, let’s clarify what these two terms actually mean.

• mAh (Milliamp-Hours)

This measures the battery’s capacity, indicating how much charge it can hold. A higher mAh value means more energy storage. For example, a 10,000mAh power bank holds more charge than a 5,000mAh one.

• Wh (Watt-Hours)

This indicates how much usable energy the battery can provide. While mAh reflects the battery’s size, Wh reveals how much power it can actually deliver to your devices.

Why Convert mAh to Wh for Power Banks?

Understanding how to convert mAh to watt-hour is important for several reasons:

Accurate Comparisons: Two power banks with the same mAh rating can provide different energy outputs depending on their voltage. Comparing Wh gives a clearer picture of their performance.

Airline Regulations: Many airlines set a maximum allowable capacity for power banks at 100Wh, making it essential to know how to convert mAh to watt-hour to stay compliant when traveling.

How to Convert mAh to Watt-Hours

To convert mAh to watt-hour, you need to know the battery’s mAh rating and its voltage (usually 3.7V for lithium-ion batteries). The formula is:

Wh = mAh × Voltage (V) / 1000

Example: Imagine two 10,000mAh power banks—one operating at 3.7V and the other at 5V:

• At 3.7V: 10,000 × 3.7 / 1000 = 37Wh
• At 5V: 10,000 × 5 / 1000 = 50Wh

When converting mAh to Wh, voltage is a key factor because it affects the total energy calculation. Based on the example, a 10,000mAh power bank at 3.7V offers 37Wh, while one at 5V provides 50Wh. This shows that voltage can significantly change the amount of usable energy.

mAh to Wh Conversion Table

This table makes it easier to estimate usable energy at different capacities.

How to Convert Watt-Hours to mAh

Now, let’s explore how to convert watt-hours to mAh if you have a power bank with a Wh rating and need to find its mAh capacity.

Formula: mAh = Wh × 10,00 Voltage (V) / 1000​

Example: Imagine you have a power bank rated at 50 Wh and 5V. To convert Wh to mAh:

mAh = 50 × 1000 / 5 = 10,000mAh. So, a 50 Wh power bank at 5V will give you 10,000mAh.

Wh to mAh Conversion Table

Voltage, Amps, and Charging Power

To make sense of these conversions, it’s important to understand the role of voltage and amps. Voltage impacts the total energy output of a power bank, while amps determine the charging speed. Together, these specifications help you interpret mAh and Wh ratings and choose the best power bank for your needs.

• Voltage (V): Most smartphones charge at 5V, but laptops and tablets might need higher voltages (e.g., 9V, 12V, or 20V). Power banks supporting Quick Charge (QC) or Power Delivery (PD) can provide these higher voltages.
• Amps (A): This determines how quickly your device charges. For example, 2.4A is ideal for smartphones, while 3A–4A suits larger devices like tablets and laptops.

Tip: Ensure the power bank’s voltage and amps match your device’s requirements for optimal charging.

How Many Times Can a Power Bank Charge Your Phone?

To estimate:

• Know the power bank’s capacity (mAh).
• Check your device’s battery capacity (mAh).
• Factor in efficiency (~85% due to energy loss).

Formula: Number of Charges = Power Bank Capacity (mAh) × Efficiency/Phone Battery Capacity (mAh)

Example: A 10,000mAh power bank (85% efficiency) charging a phone with a 3,000mAh battery:

Number of Charges = 10,000mAh x 0.85 efficiency/3000mAh

Number of Charges = 2.8 charges (2 full charge and some)

Charging Speed: How Long Does It Take?

The time to fully charge a device depends on the power bank’s output and the phone’s battery size.

Formula: Charging Time (hours) = Phone Battery Capacity (mAh)

Example: Imagine a phone with a 3,000mAh battery being charged by a power bank with an output of 2A (2,000mA).

Charging Time (hours) = 3,000mAh / 2,000 mAh

Charging Time (hours) = 1.5 hours

Estimated Number of Charges and Charging Times Table

Here’s an easy-to-understand table that breaks down how many times a power bank can charge different phones and the estimated charging time based on common capacities and speeds:

Explanation of Columns:

1. Power Bank Capacity (mAh): The total energy the power bank can store.
2. Phone Battery Capacity (mAh): The energy your phone’s battery can hold.
3. Efficiency (85%): Accounts for energy lost during charging due to heat and conversion.
4. Usable Power (mAh): The actual energy the power bank can deliver to your phone.
5. Number of Charges: How many full charges the power bank can provide for your phone.
6. Charging Time: How long it would take to charge your phone fully using a 5V/2A power bank output.

Other Considerations

• Cable Quality: Poor-quality cables may reduce charging efficiency and speed.
• Charging Protocols: Ensure the power bank supports the same protocol as your phone (e.g., Quick Charge, Power Delivery).
• Power Bank Features: Features like multiple ports or simultaneous charging may affect speed and efficiency.

Wrapping It Up

Understanding how to convert mAh to watt-hour, convert watt-hours to mAh, and the role of voltage and amps is key to making the most out of your power bank. Knowing these factors helps you pick a power bank that’s not only compatible with your device but also capable of delivering the performance you need.

Key Takeaways:

• Compare Wh, Not Just mAh: Wh provides a clearer understanding of usable energy.
• Check Charging Specs: Ensure the power bank supports your device’s voltage and amps.
• Look for Features: Fast-charging protocols like Quick Charge (QC) or Power Delivery (PD) can make a big difference.

We hope this guide helps you make a more informed decision. Happy charging!

Frequently Asked Questions

How many mAh is 1 Wh?

To convert watt-hours (Wh) to milliamp-hours (mAh), you need to know the battery's voltage. 

The formula is: mAh = (Wh x 1,000) / Voltage (V)

For example, if you have a 1 Wh battery at 3.7V, it would be:

mAh = (1 × 1000) / 3.7 = 270 mAh. So, 1 Wh is approximately 270 mAh at 3.7V.

How to calculate watt-hour of a power bank?

To find the watt-hour (Wh) of a power bank, use this formula:

Wh = (mAh × Voltage (V)) / 1000

For example, a 10,000mAh power bank at 3.7V would be:

Wh = (10,000 × 3.7) / 1000 = 37 Wh. This means a 10,000mAh power bank at 3.7V holds 37 Wh of energy.

How many watt-hours is a 5000mAh battery?

To convert a 5000mAh battery to watt-hours, use the formula:

Wh = (mAh × Voltage (V)) / 1000

Assuming the voltage is 3.7V:

Wh = (5000 × 3.7) / 1000 = 18.5 Wh. So, a 5000mAh battery at 3.7V has 18.5 Wh.

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