How long will a 12 volt battery run a 12 volt fridge?
A 12V battery typically runs a 12V fridge for 8–48 hours, depending on battery capacity (Ah), fridge efficiency, and ambient temperature. For example, a 100Ah lithium battery (80% usable) running a 5A fridge with a 50% duty cycle lasts ~32 hours. Lead-acid batteries (50% usable) halve runtime. Always match battery chemistry to usage patterns—LiFePO4 handles deeper discharges better than AGM.
What factors determine a 12V fridge’s runtime?
Runtime hinges on battery capacity, fridge energy draw, and depth of discharge (DoD). A 100Ah LiFePO4 battery (80% DoD) paired with a 60W fridge (5A) lasts ~19 hours at 50% duty cycle. Ambient temperatures above 25°C can slash efficiency by 30%.
To calculate runtime, use: (Battery Ah × DoD) ÷ (Fridge Amp Draw × Duty Cycle). For instance, a 200Ah AGM battery (50% usable) running a fridge drawing 6A with a 40% cycle provides: (200 × 0.5) ÷ (6 × 0.4) = ~41.6 hours. But real-world variables like frequent door openings or poor insulation often cut this by 25%. Pro Tip: Install a battery monitor to track actual consumption—manufacturers’ wattage labels often underestimate hot-climate usage. Think of it like a gas tank: a bigger battery (larger tank) and efficient fridge (better mileage) maximize miles.
| Battery Type | Usable Capacity | Cycle Life |
|---|---|---|
| LiFePO4 | 80-90% | 3,000–6,000 |
| AGM | 50% | 500–1,200 |
How does fridge size impact battery drain?
Larger fridges (e.g., 80L vs. 40L) require stronger compressors, increasing average draw from 4A to 8A. A 50L fridge might cycle 6x/hour for 10 minutes, while a compact 20L unit cycles 4x/hour, reducing daily Ah consumption by 35%.
Consider compressor type too—Danfoss Secop units use 30% less power than generic models. For example, a 60L fridge with a 0.7 amp-hour per liter ratio would drain a 100Ah LiFePO4 battery in ~28 hours. Pro Tip: Pre-chill food before loading to reduce initial compressor workload. Imagine two cars: a heavy SUV (large fridge) guzzles battery “fuel” faster than a compact hatchback (small fridge).
RackBattery Expert Insight
FAQs
Yes, with sufficient panel wattage (200W+ for 100Ah batteries) and sunlight. A 300W solar array can recharge a 50% depleted 100Ah LiFePO4 in 4–5 hours, maintaining 24/7 fridge operation.
Is a 12V or 120V fridge better for battery life?
12V DC fridges avoid inverter losses (up to 15% with AC units). A 120V fridge drawing 5A AC would pull 6.25A DC from batteries after conversion losses, reducing runtime by 20%.