Battery Runtime Calculator – 12V

Q: How long will a 12V 100Ah battery last?

Runtime = (Ah × DoD × Efficiency) ÷ (Watts ÷ Voltage). For a 100Ah 12V battery at 50% DoD, 90% efficiency, running a 100W load: Runtime = (100 × 0.5 × 0.9) ÷ (100 ÷ 12) = 45 ÷ 8.33 = 5.4 hours.

Q: What is a common 12V battery use?

12V batteries are used in: cars and trucks (starter batteries), caravans and RVs (leisure batteries), boats, solar off-grid systems, camping power banks, UPS systems, and backup power for 12V appliances like fridges and lighting.

Q: What depth of discharge can I use on a 12V lead-acid battery?

For 12V sealed lead-acid (AGM, gel): 50% DoD maximum for good cycle life. For 12V lithium (LiFePO4): 80–90% DoD. Discharging a lead-acid battery below 50% repeatedly causes sulfation and permanent capacity loss within 50–200 cycles.

The most common battery voltage for portable and automotive use. Enter your 12V battery's Ah rating, the load in watts, and depth of discharge — get runtime in hours and minutes. Covers lead-acid, AGM, gel, and LiFePO4 12V batteries.

Calculate 12V Battery Runtime

Battery Capacity (Ah)

Battery Voltage (V)

Load (Watts)

Depth of Discharge (%)Lead-acid: 50% max. Lithium: 80–90%

Inverter/System Efficiency (%)

Runtime Results

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Runtime (hours)

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Hours & Minutes

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Usable Energy (Wh)

Formula

Usable Wh = Ah × Voltage × (DoD ÷ 100) × (Efficiency ÷ 100)
Runtime (hrs) = Usable Wh ÷ Load Watts

Common 12V Battery Runtimes at 50% DoD, 90% efficiency

Battery	Usable Wh	50W Load	100W Load	200W Load
12V 50Ah	270 Wh	5.4 hrs	2.7 hrs	1.35 hrs
12V 100Ah	540 Wh	10.8 hrs	5.4 hrs	2.7 hrs
12V 150Ah	810 Wh	16.2 hrs	8.1 hrs	4.05 hrs
12V 200Ah	1,080 Wh	21.6 hrs	10.8 hrs	5.4 hrs

Frequently Asked Questions

How long will a 12V 100Ah battery last?

At 50% DoD and 90% efficiency: 100 × 12 × 0.5 × 0.9 = 540 Wh usable. At 100W load: 540 ÷ 100 = 5.4 hours. At 60W load: 540 ÷ 60 = 9 hours. With lithium at 80% DoD: 100 × 12 × 0.8 × 0.95 = 912 Wh ÷ 100W = 9.1 hours.

What is a common 12V battery use?

12V systems are standard for: automotive (starter batteries, not deep cycle), marine and RV leisure batteries (deep cycle for camping appliances, lights, fridges), caravan solar systems, portable power stations, UPS for small devices, and off-grid lighting. For larger off-grid systems, 24V or 48V is preferred as it reduces current and allows thinner cables.

What depth of discharge can I use on a 12V lead-acid battery?

Lead-acid (flooded, AGM, gel): 50% DoD maximum for typical 300–500 cycle life. Discharging to 80% DoD drops cycle life to under 100 cycles. For maximum life, keep DoD under 30%. LiFePO4 lithium: designed for 80–90% DoD with 2,000–5,000+ cycle life. The higher upfront cost of lithium typically pays back through dramatically longer service life and more usable capacity.