Battery Runtime Calculator
Estimate how long a battery will last from capacity and load—instant battery life / runtime for DC packs (Ah, V, A or W). Not a UPS inverter model.
Calculator
Quick: Ah + load amps → hours. Advanced: mAh/Wh, watts load, DoD, efficiency, or reverse Ah sizing.
About this calculator
This battery runtime calculator (also called a battery life calculator) estimates hours from DC capacity and load. It is not an APC/Eaton UPS selector and not a multi-day solar autonomy tool. For UPS inverter packs use UPS runtime; for Ah procurement use UPS battery sizing. Browse the power calculator hub.
Calculation Results
≈ 20.00 hours (20 h)
100 Ah · 5 A · DoD 1.00 · η 1.00
Formula: hours = (Ah × DoD × η) ÷ I
Idealized estimate—Peukert effect, temperature, and pulsed loads can shorten real hours. Treat as screening only.
Battery runtime quick reference
Ideal hours at DoD 1.0 and η 1.0 (no Peukert). Open a row to load the calculator.
| Pack | Load | Ideal runtime |
|---|---|---|
| 1 A | 7 h | |
| 5 A | 20 h | |
| 60 W | 20 h | |
| 100 mA | 20 h |
Battery runtime formula & explanation
hours = (Ah × DoD × η) ÷ I
With a watt load: hours = (Ah × V × DoD × η) ÷ W (same as converting W to amps with I = W ÷ V).
- Ah — amp-hour capacity (mAh ÷ 1000; Wh ÷ V).
- DoD — usable fraction of nameplate capacity.
- η — DC path / converter efficiency (≤ 1).
- I / W — average load current or power.
Example: 100 Ah, 12 V, 60 W, DoD 1.0, η 1.0 → I = 5 A → 20 hours.
Wh ↔ Ah: Ah = Wh ÷ V. Solar multi-day bank sizing: solar battery bank / autonomy. UPS minutes: UPS runtime calculator.
When to use which battery tool
| Goal | Tool |
|---|---|
| DC pack hours from Ah / V / load | This page — battery runtime |
| UPS backup minutes (inverter + kVA) | UPS runtime calculator |
| Required Ah for UPS target minutes | UPS battery sizing |
| Series/parallel string layout | UPS battery bank |
| Solar days of autonomy (kWh) | Solar battery bank calculator |
Frequently Asked Questions
How do I calculate battery runtime?
Hours ≈ (Ah × DoD × η) ÷ I. With watts: hours ≈ (Ah × V × DoD × η) ÷ W. Example: 100 Ah at 12 V into 60 W ≈ 20 hours at ideal DoD/η.
Is this a battery life calculator?
Yes. Battery life and battery runtime here mean how long a DC pack can power a constant load. Enter Ah/mAh/Wh and A/mA/W above.
How is this different from a UPS runtime calculator?
This page is a DC energy-balance screen. The UPS runtime calculator models inverter efficiency, UPS kVA headroom, and OEM-oriented backup minutes.
How do I convert Wh to Ah?
Ah = Wh ÷ V. Example: 120 Wh at 12 V = 10 Ah. Select Wh as capacity unit and enter voltage, or convert first.
Does depth of discharge change runtime?
Yes. Usable Ah ≈ nameplate × DoD. At DoD 0.5, planned hours are about half the DoD 1.0 ideal case before other losses.