How long will a 100Ah battery run a fridge?

A 100Ah battery’s runtime for a fridge depends on the fridge’s power consumption, battery voltage, and discharge depth. For a 12V 100Ah lithium battery (1.2kWh usable energy at 80% depth of discharge) powering a 150W fridge running 8 hours daily, the battery lasts approximately 1.6 days. Lead-acid batteries with 50% discharge depth reduce runtime to ~1 day. Actual duration varies with inverter efficiency (10–15% loss), ambient temperature, and fridge compressor cycles.

How long will a 48V 100Ah battery last?

What factors determine fridge power consumption?

Fridge compressor cycles and ambient temperature critically impact energy use. A 10°C room temperature increase can double compressor runtime. Modern inverter fridges use 30% less energy than conventional models through variable-speed compressors.

Deep Dive:
A typical 150L household fridge draws 100–200W when active, but only operates its compressor 30–50% of the time. Over 24 hours, this creates an average consumption of 1–1.5kWh. Pro Tip: Use a kill-a-watt meter for exact measurements—manufacturer labels often list peak rather than average wattage. For example, a 12V/100Ah battery (1.2kWh usable) powering a 1.2kWh/day fridge would theoretically last 24 hours, but real-world inefficiencies reduce this by 15–20%.

How does battery voltage affect runtime?

Voltage determines energy capacity—a 24V 100Ah battery stores twice the energy of a 12V equivalent. Higher voltage systems reduce current draw, minimizing energy loss in cables.

Deep Dive:
Energy (Wh) = Voltage × Amp-hours. A 12V/100Ah battery provides 1.2kWh, while 24V/100Ah delivers 2.4kWh. When powering a 100W fridge:
– 12V system: 1.2kWh ÷ 0.1kW = 12h theoretical runtime
– 24V system: 2.4kWh ÷ 0.1kW = 24h

However, what many overlook is Peukert’s Law—higher current draws (from lower voltages) reduce effective capacity. At 12V pulling 8.3A (100W ÷ 12V), a lead-acid battery might only deliver 90Ah instead of 100Ah. Pro Tip: Use lithium batteries for high-current applications—they maintain >95% capacity even at 1C discharge rates.

*With 10% efficiency loss

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How does depth of discharge impact battery lifespan?

Shallow cycling prolongs battery life—discharging lithium to 20% instead of 80% depth can triple cycle count. Lead-acid batteries degrade rapidly below 50% discharge.

Deep Dive:
A lithium iron phosphate (LiFePO4) battery cycled to 80% DoD achieves 3,000–5,000 cycles, while 100% DoD reduces this to 1,500 cycles. For a fridge running 24/7, this translates to:
– Conservative 50% DoD: 8–13 years lifespan
– Aggressive 80% DoD: 4–6 years

But why does this matter for runtime calculations? Each cycle effectively “spends” battery longevity. Pro Tip: Oversize your battery bank by 30%—this allows maintaining 70% DoD while meeting daily needs, dramatically extending service life.

What inverter losses occur in DC-AC conversion?

Inverter efficiency typically ranges 85–95%, with losses increasing under low loads. A 1,500W inverter powering a 100W fridge may waste 20–30W idling.

Deep Dive:
Modern pure sine wave inverters achieve peak efficiency (93–95%) at 70–90% load. At 10% load (e.g., 100W on 1,000W inverter), efficiency drops to 85–88%. For a 12V/100Ah system:
Total energy: 1.2kWh × 85% efficiency = 1.02kWh usable
Runtime for 1.2kWh/day fridge: ~20 hours

Real-world example: A 12V/100Ah battery with 90% efficient inverter powers a fridge consuming 1.5kWh daily. Adjusted energy: 1.2kWh × 0.9 = 1.08kWh. Daily deficit requires recharging every 17 hours. Pro Tip: Use DC-powered fridges when possible—they avoid 10–15% inverter losses entirely.

How do temperature extremes affect performance?

Cold reduces battery capacity (3% per °C below 20°C), while heat accelerates degradation. Lithium handles -20°C to 60°C but charges poorly below 0°C.

Deep Dive:
At -10°C, a lead-acid battery’s capacity drops 40%—a 100Ah battery effectively becomes 60Ah. Lithium fares better, retaining 80% capacity at -20°C. However, charging below freezing requires heated lithium batteries. For Arctic applications, calculate runtime at 50–60% rated capacity. Conversely, 35°C ambient temperatures halve lead-acid lifespan but only reduce lithium cycle life by 20%.

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