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A practical power bank charges scenario
For this example, use power bank capacity of 100 Wh, device battery capacity of 18 Wh, and transfer efficiency of 75 %. These are starting values, so replace them with numbers that match your situation.
Power bank capacity: 25% lower
Change power bank capacity to 75 Wh while keeping the other example values the same.
Power bank capacity: 25% higher
Change power bank capacity to 125 Wh while keeping the other example values the same.
Interactive chart
See what changes the result
This result is categorical, so compare the calculated values in the examples and snapshots instead.
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Quick answer
What does the Power bank charges calculate?
How many effective device charges can a power bank provide? This calculator uses power bank capacity, device battery capacity, and transfer efficiency to estimate effective device recharges immediately in your browser.
With the values currently entered, the result is 4.2 charges — effective full recharges. It also shows usable power-bank energy, and conversion loss.
How to use the Power bank charges
- Replace the example values with your own numbers.
- Review the result and supporting figures as they update automatically.
- Check the formula and assumptions before using the estimate for a decision.
Inputs used
- Power bank capacity — entered in Wh
- Device battery capacity — entered in Wh
- Transfer efficiency — entered in %
Power bank charges formula
Power-bank watt-hours × efficiency ÷ device watt-hours
Assumptions
- Both capacities use watt-hours.
- Device use during charging is excluded.
Practical guide
Power bank charges example and edge cases
How many effective device charges can a power bank provide? Let's use a concrete example, then look at the assumptions that can move the answer.
Example: A practical power bank charges scenario
For this example, use power bank capacity of 100 Wh, device battery capacity of 18 Wh, and transfer efficiency of 75 %. These are starting values, so replace them with numbers that match your situation.
- Power bank capacity
- 100 Wh
- Device battery capacity
- 18 Wh
- Transfer efficiency
- 75 %
Calculated result4.2 chargeseffective full recharges
Start with effective full recharges. Then check usable power-bank energy, and conversion loss to understand what sits behind the main result.
Example results use the default display profile. The calculator above follows your selected country and units.
How to read the result
- Read the main result first. The supporting figures for usable power-bank energy, and conversion loss explain how the estimate is built.
- The method is Power-bank watt-hours × efficiency ÷ device watt-hours. Keep the units consistent and use values from the same time period.
Edge cases worth checking
When power bank capacity is unusual
Both capacities use watt-hours. Double-check this input before relying on the result.
When transfer efficiency is uncertain
Device use during charging is excluded. Run a lower and higher value to see a useful range.
What changes the result most
Power bank capacity
Change power bank capacity on its own first. This shows how strongly it affects the answer.
Device battery capacity
Change device battery capacity on its own first. This shows how strongly it affects the answer.
Transfer efficiency
Test a lower and higher transfer efficiency. A small percentage change can move the final result more than expected.
Try a different scenario
Small changes show whether the answer is stable or sensitive.
Power bank capacity: 25% lower
75 Wh3.1 chargeseffective full recharges
Power bank capacity: 25% higher
125 Wh5.2 chargeseffective full recharges
Device battery capacity: 25% higher
23 Wh3.3 chargeseffective full recharges
Common mistakes
Check power bank capacity
Both capacities use watt-hours. Make sure this matches the number you enter.
Keep transfer efficiency consistent
Device use during charging is excluded. Use the same units and time period throughout the calculation.
Do not rely on one power bank charges scenario
Run a cautious case and an optimistic case. The range is often more useful than one exact-looking number.
Use this result well
How many effective device charges can a power bank provide?
Real speed, compression, battery health, and device overhead can change the result.