Battery & Solar Runtime Calculator

Estimate how long your device will run on a battery pack or a capacitor bank, with optional solar assist. Adjust load, cell/cap bank, and capacity — results update instantly.

Quick Estimate

Just the essentials. Change these and your KPIs update instantly.

Average device power (W)

Power path efficiency (%)

Units in series (S)

Units in parallel (P)

Nominal cell voltage (V)

Capacity per cell (mAh)

Use solar assist Enable if you have a panel

Panel power (W)

Sun hours per day

Usable DoD (%)

Battery-only parameter

Runtime (no solar)

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Runtime (with solar)

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Daily use

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Daily solar input

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Tip: Switch to Advanced for tilt, azimuth, obstructions, and voltage-point modeling.

Device

Input method

New: derive draw from OCV

Average entry mode

Pick direct W or auto-calc

Average power draw (W)

Voltage entry type

Reading condition

Chemistry

Add ≥ 2 points. We convert volts → SOC using the selected chemistry’s OCV curve (rested ≈25 °C); then fit a slope for SOC/hour. If you enter pack volts, we divide by S to get per-cell.

Timestamp	Voltage

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Power path efficiency (%)

Usable DoD (%)

Efficiency covers DC/DC losses, wiring, and conversion. DoD is the fraction of pack capacity you plan to use (battery mode only).

Energy Source

Source type

Switch to model supercaps or RC hold-up

Units in series (S)

Units in parallel (P)

Nominal cell voltage (V)

Capacity per cell (mAh)

For Li-ion 18650/21700 cells, 3.6–3.7 V nominal is typical.

⚠️ When installing new lithium cells, ensure all cells are properly balanced before use.
For parallel configurations, the voltage difference between cells should be no more than 0.05 V (50 mV).
Larger differences can cause large equalization currents, leading to overheating or cell damage.

Solar (optional)

Enable solar assist uncheck if no panel

Panel power (W)

Sun hours per day

Simplified model: panel contributes Panel W × Sun hours Wh per day to offset consumption.

Enable time & position modifiers

Latitude (°)

Panel tilt from horizontal (°)

Date

Panel azimuth (° from North)

Skyline obstruction

Custom uniform (°)

Sector obstructions (optional)

Start az (°)	End az (°)	Height (°)

Azimuths are North-clockwise (0°=N, 90°=E, 180°=S, 270°=W). Height is skyline elevation.

Assumes clear sky. Uses sun angle & air-mass to scale panel power. Obstruction reduces effective sun-hours.

Panel Orientation Visualizer

North is up (0°). Angles increase clockwise.

Panel azimuth (your input). Tilt shown numerically.

Sun azimuth (yellow) if sun is above skyline; dim when blocked.

Tilt —°, Sun elev —°, Air mass —, Incidence loss —%

The dial uses your latitude, day-of-year, tilt & azimuth. It reuses the same clear-sky position model as the solar factor.

Pack voltage (nominal)

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Pack capacity (usable Ah)

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Pack energy (usable Wh)

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Device input power (incl. losses)

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Runtime with no solar

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Runtime with solar (avg)

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Daily consumption

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Daily solar input

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