Battery pack runtime for LEDs
Estimate hours a battery pack or power bank will run LED lights from capacity (mAh), pack voltage, and LED watt draw.
Wh = (mAh ÷ 1000) × V × usable% · hours = Wh ÷ LED_watts
When to use
This tool helps when you want a battery pack runtime for leds planning figure with the assumptions written down. You will enter battery capacity (mah), pack nominal voltage (v), led load (watts), and usable capacity / efficiency (%).
Estimate hours a battery pack or power bank will run LED lights from capacity (mAh), pack voltage, and LED watt draw. Keep units consistent (feet vs inches, watts vs amps), then use the formula box to see how each term contributes.
Stop and ask a licensed electrician when loads, hardwired outlets, or roof work go beyond temporary plug-in holiday displays.
USB power banks often use 3.7 V cells; 5 V output has converter loss — fold into usable %.
Strand watts, or volts × amps from the label.
Accounts for cutoff, cold weather, and boost-converter losses.
Worked example
Example inputs from the form defaults — Battery capacity (mAh) = 10000; Pack nominal voltage (V) = 3.7; LED load (watts) = 3; Usable capacity / efficiency (%) = 80 — are plausible homeowner figures, not a survey of your roofline.
Compute with: Wh = (mAh ÷ 1000) × V × usable% · hours = Wh ÷ LED_watts. Show intermediates before the final count or cost.
When the calculator and scratch math disagree, fix units first; the battery pack runtime for leds model is only as good as consistent inputs.
Limits / assumptions
Assumptions: inputs match the hints (measured eaves, nameplate watts, package strand length, and so on). Terms not named in the formula are not secretly included.
Limits: outdoor weather, GFCI trips, and real stock sizes vary. Prefer outdoor-rated cords and clips; ladder and roof work need their own safety practices.
Responsibility: confirm safety-critical electrical and height decisions with manuals and, when needed, a qualified professional. PWC Lights does not stamp displays.
Cold outdoor nights reduce real capacity. Use packs rated for your lights and keep connections dry. Not a substitute for manufacturer runtime charts.
FAQ
mAh vs Wh?
Watt-hours = (mAh/1000) × volts. Runtime is Wh ÷ load watts.
USB 5 V banks?
Cell is often 3.7 V; the 5 V boost wastes some energy — keep usable % around 70–85%.
AA battery boxes?
Enter pack voltage (e.g. 4.5 or 6 V) and estimated mAh for the cell type in series/parallel.
Timers help?
Shorter nightly on-time multiplies calendar nights from the same charge.