Want to know how long a mini fan can run on a lithium-ion battery? Here are the facts and the math that backs them up.
I’m a numbers person. I’m one of those very left-brained, logical, give-me-the-figures kind of person.
Underneath it all, I know that a product is only as good as its weakest part.
I know that performance and value are the sum of all the pieces and processes that, together, create a product.
I’ve reviewed lots of these fans and I’ve seen run times reported anywhere from 2-24 hours.
Of course, it all comes down to a number of factors – battery size, fan size, temperature, and more.
So that I could better compare reported specs, I went on the hunt to understand what you need to know in order to calculate how long a small, personal fan can run on a single charge.
Data to Gather
What information would you have to gather in order to calculate the run time of a mini fan running on a rechargeable lithium-ion battery?
You would need the following information:
- Battery Capacity (mAh or Ah): This is the most critical piece of information. Battery capacity tells you how much charge the battery can store. It’s usually measured in milliampere-hours (mAh) or ampere-hours (Ah). You can find this information on the battery itself or in the product’s specifications.
- Fan’s Current Draw (mA or A): The mini fan’s current draw, which is the amount of current it consumes while operating, is essential. You can usually find this information in the fan’s manual or on its label. It’s also measured in milliamperes (mA) or amperes (A).
- Voltage of the Battery (V): Lithium-ion batteries typically have a nominal voltage of 3.7 volts, but it can vary. Make sure you use the correct voltage for your specific battery.
The Math
With these three pieces of information, you can calculate the run time (in hours) of the mini fan using the following formula:
Run Time (hours)=Battery Capacity (mAh or Ah)Fan’s Current Draw (mA or A)×Battery Voltage (V)1000Run Time (hours)=Fan’s Current Draw (mA or A)Battery Capacity (mAh or Ah)×1000Battery Voltage (V)
Let’s use an example to illustrate this:
Suppose you have a mini fan with a battery capacity of 2000mAh and it operates at a current draw of 100mA. The battery voltage is 3.7V.
Run Time (hours)=2000 mAh100 mA×3.7 V1000=7.4 hoursRun Time (hours)=100 mA2000 mAh×10003.7 V=7.4 hours
So, in this example, the mini fan would run for approximately 7.4 hours on a fully charged 2000mAh lithium-ion battery.
Remember that this is a theoretical calculation and doesn’t account for factors like battery efficiency, temperature, and discharge curve variations, which can affect the actual run time. It provides a good estimate under ideal conditions.
If you have the specific values for your mini fan and battery, you can plug them into the formula to get a precise run time estimate.
Lacking Draw & Voltage?
The challenge is that most product pages for these small fans only report the battery capacity.
If you have a mini fan that provides the battery capacity but not the current draw or voltage, you can still compare their run time potential to some extent.
Here’s how you can do it:
- Battery Capacity (mAh or Ah): Start by comparing the battery capacities of the different fans. The higher the capacity, the longer the fan is likely to run. A fan with a higher mAh or Ah rating will generally provide longer run time.
- Check for Common Voltages: While the voltage may not be specified for the fan, you can assume a common nominal voltage for lithium-ion batteries, which is typically 3.7V. Most small electronic devices like mini fans use this voltage. Keep in mind that if the actual voltage is significantly different, it can affect the run time, but this is a reasonable assumption for general comparisons.
- Look for Efficiency Information: Check if the product descriptions or user reviews provide any information about the fan’s efficiency or energy-saving features. Fans with efficient motors or variable speed settings may use less power and run longer on the same battery capacity.
- Consider Real-World Feedback: Reading user reviews or seeking advice from others who have used the same fan model can provide valuable insights into its actual run time. Users often share their experiences with battery life and may mention how long the fan runs on a single charge.
- Test it Yourself: If possible, you can also conduct a practical test by fully charging the fan’s battery and running it continuously until it stops. While this won’t give you an exact current draw, it will give you a real-world run time for that specific fan under your conditions.
Keep in mind that these methods provide estimations and comparisons rather than precise run time calculations. They can help you make an informed decision when choosing a mini fan based on battery life, even when you don’t have detailed technical specifications.