How to Estimate Battery Runtime
When this applies
Use this guide when you need a quick autonomy estimate with transparent assumptions before reviewing discharge curves, load variation, or BMS limits.
Tool to use
Runtime from watt-hours or Ah×V, load power, efficiency, and depth of discharge.
Open Battery Runtime Calculator →Steps
- 1Choose whether your known energy basis is watt-hours directly or amp-hours times nominal voltage.
- 2Set the average load power in watts for the period you want to screen.
- 3Apply realistic efficiency and usable depth-of-discharge factors instead of assuming full nameplate energy.
- 4Compute runtime and compare it to your required autonomy target.
- 5Escalate to chemistry-specific discharge and ageing data for real design decisions.
Examples
- Sizing backup time for a small DC control panel.
- Checking whether a battery pack can cover a constant field load through an outage window.
What to avoid
- Treating nameplate energy as fully usable in all conditions.
- Ignoring inverter or conversion losses in AC-backed systems.
- Using a constant-load estimate as if it represented a variable real-world profile.
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Browse all task guides or see the full list on the Generators & Calculators hub.
FAQ
Is this a cycle-life tool?
No. It estimates runtime only and does not model battery ageing or cycle-life tradeoffs.
Can I use it for any chemistry?
Only as a first-pass energy estimate. Chemistry-specific voltage and discharge behavior still matter.