Check energy and output limits for ordered load phases using the bank inputs on this page.
Battery & Power
Estimate power bank runtime
Compare usable power-bank energy with the connected load to estimate continuous or duty-adjusted operating time.
Calculation breakdown
Estimate only. Runtime assumes the entered load factor represents average power divided by active power, the displayed charge is proportional to stored energy, and the selected port/profile can supply the active load. Actual runtime can change with idle draw, load variation, conversion losses, automatic cutoff, temperature, battery condition, cable capability and device behavior.
Check an ordered power-use plan
Use bank capacity, available charge, reserve and delivery efficiency above. List non-overlapping phases in time order. Each watt value is the total simultaneous load during that phase; include any idle draw in it. The original single-load factor and port limit are not applied to this separate phase plan.
Choose a steady load or an ordered power-use plan
The original form estimates runtime for one representative average load, with direct watts or voltage/current input, an average-load factor and an optional port/profile limit. The additional phase plan answers a different question: will a sequence of specified loads and durations fit the energy budget, and which phase would run out first?
Start with usable delivered energy
Rated Wh = label Wh, or rated mAh × paired internal-cell voltage ÷ 1,000. Usable delivered Wh = rated Wh × (available charge % − reserve charge %) ÷ 100 × delivery efficiency % ÷ 100. The reserve is a planned ending charge, so it cannot exceed the available charge. Equal values leave zero modeled energy.
Use the voltage paired with the capacity label, rather than automatically choosing a 5 V USB port voltage. The manufacturer’s label explanation distinguishes battery energy and port specifications. Port watts describe instantaneous delivery capability; stored Wh describe an energy budget.
Read the original steady-load estimate
For voltage/current input, active watts = load V × load A. Average watts = active watts × average-load factor % ÷ 100. Runtime hours = usable delivered Wh ÷ average watts. The factor should include relevant idle energy: a device active half the time does not necessarily average half its active watts if it also draws power while idle.
The optional original output limit applies to the actual port and profile used by that load. Having enough Wh does not mean the bank can deliver the required watts or negotiate the required voltage. Human-readable runtime rounds to minutes, while underlying values may contain additional precision.
Build sequential phases correctly
Each new phase is a non-overlapping interval. Its watts are the combined simultaneous load during that interval, and its hours are the interval duration. For example, do not list a laptop and light as separate sequential phases if they actually operate together. Instead enter their combined watts for the shared interval, followed by any period when only one remains on.
Phase energy Wh = total simultaneous watts × phase hours. The table accumulates that demand in order. If a phase needs more than the remaining budget, its possible energy-only duration is remaining delivered Wh ÷ phase watts. The first unfinished phase and elapsed time from plan start identify where the assumed plan fails. Later phases are not treated as independently receiving a fresh battery.
A 74 Wh bank at 100% charge, 10% reserve and 85% delivery efficiency provides 56.61 Wh. One hour at 30 W followed by four hours at 5 W needs 50 Wh, leaving 6.61 Wh. Extending the second phase to six hours needs 60 Wh: energy runs out 5.322 hours into that phase, or 6.322 hours after the plan starts.
Check power separately from energy
Each phase accepts an optional applicable simultaneous-output limit. Use the manufacturer’s limit for the actual ports and profile combination; unknown values stay marked unknown. The original single-port limit is not silently reused as a combined multi-port rating. The original single-load factor is also not reapplied because phase watts already represent the chosen interval.
A 30 W phase fails an entered 20 W output limit even when sufficient energy exists. Its displayed energy timeline remains hypothetical; an overloaded bank may shut down immediately. A passing numerical cap does not verify individual port limits, protocols, startup transients or hardware behavior.
Boundaries and related tools
Use 1–20 phases with non-negative watts and hours up to 1,000,000 each. Optional caps must be positive. Zero-duration phases use no energy and do not perform a power check. Zero-watt waiting phases advance time without consuming modeled energy; include actual idle consumption when relevant. Plain decimals up to 18 places are compared exactly before six-place display rounding. Source or phase edits clear the old result.
This plan excludes replenishment between phases, pass-through operation, changing conversion efficiency, low-load automatic shutoff and battery aging beyond your chosen assumptions. Use Charge Count for device battery top-ups and Charging Time for refilling the bank. These browser calculations do not control equipment or save a usage schedule.