Practical guide

How to Collect Inputs for a Battery Runtime Estimate

Find battery energy, load, inverter, duty-cycle, usable-capacity, and Peukert inputs without relying on generic chemistry defaults.

Start with the exact battery document

Record the manufacturer, exact model, document revision, nominal voltage, rated Ah or Wh, capacity-rating period and cutoff/test conditions. Do not replace an exact model with a chemistry-only assumption.

If the complete product publishes watt-hours, that is usually the cleanest energy input. If it publishes amp-hours, pair the value with nominal voltage. Do not add both representations for the same stored energy.

Describe the bank topology

For identical batteries, count units in each series string and parallel strings. Check that the products are suitable to be connected as proposed; the calculator only performs arithmetic and does not approve mixing battery age, capacity, chemistry, or condition.

Build the load list

Prefer measured average watts at the relevant operating state. If only current is known, record the actual load voltage. Separate direct DC paths from AC inverter paths.

For cycling equipment, measure or estimate active power, sleep power, and representative duty percentage. Keep startup/surge suitability as a separate check because an average-energy result does not approve surge capability.

Record inverter behavior

Use efficiency at the expected load, not merely a headline peak efficiency. Record idle or no-load watts separately. One active inverter’s idle draw is counted once even if several appliance rows use it.

Choose explicit usable factors

Depth of discharge is a planned usable fraction, not a universal chemistry constant. State of health and temperature effects likewise need measurement or the exact product information. Leave values at the ideal 100% only when you want to see the unadjusted energy arithmetic, and label the result accordingly.

Use Peukert data narrowly

Peukert mode needs the rating period and battery-specific exponent. If an exponent is absent, two capacity ratings at different discharge currents may permit a derivation, but the fixed-exponent model remains an approximation. Skip it for a first-pass energy balance or when the current/voltage profile materially varies.

Verification checklist

• Exact battery and inverter model documents recorded
• Capacity basis entered once
• Nominal voltage confirmed
• Average and standby loads measured or sourced
• AC efficiency and idle draw separated
• Cutoff, BMS, continuous and surge current checked outside the estimator
• Wiring, protection, charging, temperature and installation requirements reviewed
• Assumptions exported with the result

When the inputs are ready, open the battery runtime and discharge calculator.