Is this a lithium or LiFePO4 battery runtime calculator?

Yes for DC packs—enter Ah, V, and load. Use DoD about 0.8–0.9 for many LiFePO4 packs. It is an energy-balance screen, not a BMS model.

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.

Calculation mode

Battery capacity

Nameplate capacity. Wh mode divides by voltage to get Ah.

Battery voltage (V)

Required for Wh capacity or watt loads. DigiKey-style current path works without V when load is in amps.

Load

Average draw. Watts path uses I = W ÷ V.

Battery chemistry (sets DoD / η defaults) Matches OEM runtime screens that ask chemistry—then tune DoD like Omni’s discharge safety margin.

Usable depth of discharge (DoD, 0–1) 1.0 = full nameplate (ideal). Lead-acid often 0.5; many LiFePO4 packs ~0.8–0.9.

Path efficiency η (0.5–1) Include converter/wiring losses if known. Default 1.0 for ideal DC screen.

About this calculator

This battery runtime calculator (also called a battery run time calculator, battery life calculator, or DC battery backup 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

Assumptions: constant average load; Peukert / high C-rate capacity loss is not modeled (real hours can be shorter than this screen). Temperature and pulsed loads also matter—treat as planning only.

Continue Your Calculation

Need UPS inverter backup minutes instead? Continue in the UPS Runtime Calculator (link updates from your inputs).

UPS runtime →

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
	200 W	6 h
	200 W · DoD 0.8	≈ 4.6 h
	200 W	12 h
	500 W · DoD 0.8	≈ 7.3 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).

Peukert note: This calculator uses a linear energy balance (like DigiKey/Omni capacity ÷ current screens with a safety/DoD factor). It does not apply Peukert’s law—high discharge rates reduce available Ah, so field runtime can be shorter.

Ah — amp-hour capacity (mAh ÷ 1000; Wh ÷ V).
DoD — usable fraction of nameplate capacity (chemistry presets above).
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 converter: ampere hour to watt hour calculator. Ah ÷ hours → A: Ah to amps calculator. 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.

How long will a 100Ah battery last with a 200W load?

At 12 V ideal: hours ≈ (100 × 12) ÷ 200 = 6 hours. With LiFePO4 planning DoD 0.8 and η 0.95 ≈ 4.6 hours. Use the 100 Ah · 12 V · 200 W or LiFePO4 quick example above. At 24 V the same 100 Ah lasts about twice as long at the same watts.

Is this a lithium / LiFePO4 battery runtime calculator?

Yes for DC packs—enter Ah, V, and load. Use DoD ≈ 0.8–0.9 for many LiFePO4 packs (shallower than lead-acid 0.5). It is still an energy-balance screen, not a BMS or Peukert model.

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.

Is this a battery run time calculator or battery backup calculator?

Yes for DC packs. Battery run time calculator and DC-oriented battery backup calculator searches map here (Ah × V ÷ W with DoD/η). If you mean UPS wall/inverter backup minutes, switch to the UPS runtime calculator.

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. Use the dedicated ampere hour to watt hour calculator, or select Wh as capacity unit here and enter voltage.

How do I calculate battery runtime from capacity and average current?

Hours ≈ (Ah × DoD × η) ÷ I—the same capacity ÷ average current idea used on DigiKey-style battery life screens, plus optional DoD/η. Example: 100 Ah ÷ 5 A ≈ 20 hours at DoD 1.0. Peukert is not modeled.

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. Use the chemistry presets (lead-acid / LiFePO4) to seed DoD, then fine-tune.