How long will a 12 volt battery run a 12V refrigerator?
A 12V battery’s runtime with a 12V refrigerator depends on its capacity (Ah), the fridge’s power draw (watts), and system efficiency. For example, a 100Ah lithium (LiFePO4) battery at 80% depth of discharge provides ~960Wh. A 60W fridge draws ~5A hourly, yielding ~19 hours runtime. Lead-acid batteries last 30–50% shorter due to 50% safe discharge limits. Always derate calculations by 15% for inverter/voltage losses.
What factors determine a 12V fridge’s runtime?
Runtime hinges on battery capacity, fridge energy efficiency, and operating conditions. Lithium batteries outperform lead-acid due to higher usable capacity. Ambient temperatures above 32°C can double compressor cycles, slashing runtime by 40%.
Battery capacity (Ah) multiplied by voltage (12V) gives watt-hours (Wh). Divide this by the fridge’s average wattage (e.g., 60W) for theoretical runtime. However, real-world factors like compressor start-up surges (3x rated draw) and nighttime insulation gaps reduce this. Pro Tip: Use a kill-a-watt meter to track your fridge’s actual 24h consumption. For example, a Dometic CFX3 55IM draws 0.8A in ECO mode but spikes to 8A during cooling—a 10Ah battery might only last 6 hours. Always oversize your battery bank by 25%.
How do I calculate battery runtime accurately?
Apply the formula: (Ah × Voltage × DoD) ÷ (Fridge Watts ÷ Voltage). For lithium, use 80% DoD; lead-acid, 50%. Multiply by 0.85 to account for efficiency losses.
Start by converting fridge wattage to amps: 60W ÷ 12V = 5A. A 100Ah LiFePO4 battery delivers 100Ah × 0.8 DoD = 80Ah. Divide 80Ah by 5A = 16 hours. Apply the 15% derating: 16 × 0.85 = 13.6 hours. But what if your fridge cycles on/off? If it runs 50% of the time (e.g., 2A average draw), runtime doubles. Pro Tip: Install a battery monitor with shunt sensors—Victron BMV-712 tracks real-time consumption and state of charge. In RVs, dual batteries with isolators prevent total discharge. For example, two 100Ah AGMs powering a 75W fridge provide ~24h runtime (100Ah × 2 × 12V × 0.5 DoD ÷ 6.25A = 19.2h before derating).
| Battery Type | Usable Capacity | Cycle Life |
|---|---|---|
| LiFePO4 | 80% | 3,000–5,000 |
| AGM | 50% | 500–1,200 |
Does battery chemistry affect fridge runtime?
Lithium batteries provide 60–70% longer runtime than lead-acid due to higher DoD tolerance. They also maintain voltage stability under load, preventing fridge brownouts.
Lead-acid voltage drops as they discharge—a 12V AGM at 50% DoD may output 11.8V, triggering low-voltage fridge shutdowns prematurely. Lithium stays above 12.8V until 80% DoD. Plus, lithium’s 2–3% self-discharge/month vs. lead-acid’s 5–15% makes them better for seasonal use. Pro Tip: For ice-heavy setups, choose lithium—their stable power ensures consistent compressor performance. A Yeti Tundra 45 paired with a Battle Born 100Ah lasts 22 hours, while the same fridge with a VMAX AGM lasts 9 hours. But remember: lithium costs 3x upfront but lasts 5x longer.
How does temperature impact battery performance?
Cold reduces capacity; heat accelerates degradation. Below 0°C, lead-acid loses 30–40% capacity; lithium loses 20% but can’t charge under freezing without heaters.
At 35°C, lead-acid lifespan halves every 10°C rise (per Arrhenius equation). Lithium handles heat better but avoid sustained >45°C. For Arctic camping, use AGM with insulation—their electrolyte won’t freeze until -40°C vs. lithium’s BMS cutoff at -20°C. Pro Tip: Bury batteries in cool soil during desert trips. In a test, a 100Ah LiFePO4 in direct sun at 50°C delivered only 82Ah, while a shaded one provided 95Ah. Always check your fridge’s ambient temp rating—most compressors overheat above 43°C, cycling nonstop.
| Condition | Lead-Acid Capacity | Lithium Capacity |
|---|---|---|
| -10°C | 60% | 80% |
| 40°C | 85% | 95% |
Can solar panels extend fridge runtime indefinitely?
Yes, with proper solar panel wattage and MPPT charge controllers. Panels must offset the fridge’s daily consumption plus 20% for inefficiencies.
A 60W fridge running 24/7 consumes ~1,440Wh (60W × 24h). In sunny regions, a 200W solar array generates ~1,000Wh/day (5h sun × 200W). You’d need 300W to break even. But what about cloudy days? Include a battery buffer—a 200Ah lithium bank stores 2,560Wh, covering 1.7 days without sun. Pro Tip: Use tilt mounts and solar trackers to boost yield by 25%. For example, EcoFlow DELTA Pro + 400W panels runs a 12V fridge indefinitely in summer. Warning: Partial shading on panels can cut output by 80%—keep arrays unobstructed.
How long will a 48V 100Ah battery last?
RackBattery Expert Insight
FAQs
Yes, but avoid deep discharges—car batteries are designed for short bursts, not sustained loads. Deep-cycle marine/RV batteries are safer.
How do I prevent battery drain overnight?
Set your fridge’s low-voltage disconnect 0.5V above the battery’s safe limit (e.g., 11.5V for AGM). Use a thermostat to reduce cycling in cool hours.
Do DC fridges save power vs. AC?
Yes—12V DC fridges avoid inverter losses, using 10–15% less energy. A 12V Dometic uses 45W vs. 60W for a 120V Whynter through an inverter.