12V Battery Runtime Calculator

Q: How long will a 100Ah lithium battery run a 12V camping fridge?

A standard 40L to 65L camping fridge draws about 15W to 18W on average once cycling. On a 100Ah LiFePO4 battery (providing ~90Ah usable capacity), it will run for 60 to 75 hours continuously without recharging.

Q: What is the difference between AGM and LiFePO4 usable capacity?

AGM batteries can only be safely discharged to 50% Depth of Discharge (50Ah usable from a 100Ah battery). LiFePO4 lithium batteries can be discharged to 90% DoD, delivering 90Ah of real-world energy.

1. Battery Bank Setup

Battery Chemistry

Capacity (Amp Hours)

Inverter Eff. (%)

2. Connected Loads

Quick Add Presets:

Power Draw (Watts)

Run Profile

Power Draw (Watts)

Run Profile

3. Estimated Runtime

Continuous Runtime

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Usable Energy

-- Wh

Avg Current Draw

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Recommended Off-Grid Gear

Tested hardware to match your battery and solar calculations:

→ 100Ah / 200Ah LiFePO4 Lithium Batteries

Grade-A cells, smart Bluetooth BMS, and 10+ year lifespan.

→ 200W Folding Solar Blankets & Panels

Monocrystalline portable solar with built-in MPPT regulators.

→ Pure Sine Wave Inverters (1000W–2000W)

Safe power for camping fridges, laptops, travel ovens, and chargers.

Frequently Asked Questions & 12V Sizing Guide

How long will a 100Ah lithium battery run a 12V camping fridge? +

Under standard ambient temperatures (20°C to 28°C), a typical 40L to 65L single-zone camping fridge draws around 40W to 50W while cooling. Because modern fridges cycle on and off (roughly a 35% to 40% duty cycle once down to temperature), the average draw is about 15W to 18W (1.2A to 1.4A at 12.8V).

On a 100Ah LiFePO4 battery (providing roughly 90Ah or ~1,150Wh of usable power), you can expect between 60 and 75 hours of continuous runtime (around 2.5 to 3 full days) without solar or alternator charging.

What is the difference between AGM and LiFePO4 usable capacity? +

• AGM / Lead-Acid: Should not be discharged below 50% Depth of Discharge (DoD) without damaging cell life and causing voltage sag. A 100Ah AGM only delivers 50Ah usable capacity.
• LiFePO4 Lithium: Safely discharges to 10% remaining capacity (90% DoD) for thousands of cycles while maintaining steady 12.8V output. A 100Ah lithium battery delivers 90Ah of usable power.

How much solar do I need to stay off-grid indefinitely? +

Multiply your daily continuous draw by 24 hours to find daily Wh. Divide that by (4.5 peak sun hours × 0.75 efficiency). A typical 30W continuous load draws 720Wh/day, requiring approximately a 200W to 250W solar blanket or panel to break even.

How much power does an inverter waste? +

Pure sine wave inverters run at 85% to 92% efficiency. Idle inverters also draw 0.8A to 1.5A (10W to 20W) simply being turned on, which burns roughly 15Ah to 20Ah of battery capacity overnight if left switched on.