Free planning tools · Plan an imaging night

Astrophotography battery runtime calculator

Add the equipment you actually run and estimate both runtime and the rated energy needed for your session.

No account needed. Results update here as you change the inputs. Measurements stay in this tab unless you choose to share a link; shared links contain the inputs, including any location coordinates.

Your inputs

The starting values are examples. Replace them with your own measurements, prices or documented requirements.

What to have ready
  • Measured or documented input watts for each device.
  • The battery’s nominal voltage and rated amp-hours.
  • An explicit conversion-efficiency assumption and unused reserve.
Measurements for Astrophotography battery runtime calculator
Equipment loads

Calculated from your inputs

Your plan

The example will calculate here when JavaScript is ready.

What to do next

    Calculation details

    Inputs used in this result

    Compare a change before committing

    Keep this plan, change the inputs and see the difference. The comparison stays in this tab.

    Will the telescope battery last through your planned night?

    A mount, cooled camera and computer are an energy budget together. Add the dew heaters and hubs too. This astrophotography battery calculator separates average consumption from the battery’s usable energy, so you can compare the session you want with the battery you have.

    The load breakdown shows where the energy goes. Keep a baseline before changing a battery size or equipment duty cycle; the comparison makes a proposed change easier to discuss with an astronomy club or observing partner.

    How to use this planner

    1. List every powered device and its expected duty cycle. Use 100% for a continuous load.
    2. Set planned hours, nominal battery capacity, losses and reserve.
    3. Compare the estimated runtime with the session and separately check the power supply’s current limits.

    The calculation

    Average load = Σ(watts × duty cycle). Usable Wh = volts × Ah × efficiency × (1 − reserve). Runtime = usable Wh ÷ average watts.

    A worked example

    A 55 W average load with a 12 V, 40 Ah battery, 90% efficiency and 20% reserve gives 345.6 usable Wh and about 6.28 hours.

    Example inputs are demonstrations. Replace them with your own measurements, prices or documented requirements.

    Assumptions and limits

    Example loads and allowances are illustrative. Use measured average loads where possible. Check peak output, connector ratings and battery protection separately. Cold, ageing and converter limits can reduce runtime. Avoid counting losses twice; use the nominal battery voltage for Ah conversion.

    Questions about this calculation

    Why do watt-hours matter more than an amp-hour headline?

    Amp-hours need a voltage to describe energy. The tool first multiplies nominal voltage by rated amp-hours, then applies the entered losses and reserve before calculating runtime.

    Does a good runtime estimate mean the supply handles every peak?

    No. Energy capacity and instantaneous output are different checks. The sum of entered watts is shown as a separate screening figure, but startup surges, cable ratings and connector limits need their own evidence.

    Put the result in context