What size lithium battery do I need to run a 3000 watt inverter?
To run a 3000W inverter, you’ll need a lithium battery bank sized to match your energy demands and runtime. For continuous 3000W output, calculate total watt-hours (Wh) by multiplying power (3000W) by runtime (hours). Factor in inverter efficiency (85–95%) and battery depth of discharge (DoD, typically 80% for LiFePO4). For example, a 48V 200Ah LiFePO4 battery provides 9.6kWh (48V × 200Ah × 0.8 DoD), supporting a 3000W load for ~2.5 hours. Always prioritize lithium chemistries like LiFePO4 for stability and cycle life.
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How do I calculate battery capacity for a 3000W inverter?
Use the formula: Battery Ah = (Watt-hours ÷ Voltage) ÷ DoD. For a 3000W load over 2 hours with 48V LiFePO4 (90% efficiency): 3000W × 2h = 6,000Wh; adjusted for efficiency = 6,666Wh. Divide by 48V: 138.9Ah. Factor in 80% DoD: 173.6Ah minimum. Pro Tip: Add 20% buffer for unexpected loads to avoid premature depletion.
Real-world example: A 48V 200Ah LiFePO4 battery delivers 9.6kWh usable energy. At 3,000W, runtime is ~3.2 hours. Transitioning to runtime needs, how does voltage affect sizing? Higher voltages (e.g., 48V vs. 12V) reduce current, minimizing heat and wiring costs. For 12V systems, 3000W requires 250A—impractical for most lithium batteries. Practically speaking, 48V systems dominate for high-power inverters. Need longer runtime? Double the capacity or reduce load.
| Voltage | 3000W Runtime (1h) | Minimum Ah |
|---|---|---|
| 12V | ~0.8h | 312.5Ah |
| 24V | ~1.6h | 156.3Ah |
| 48V | ~3.2h | 78.1Ah |
Why choose LiFePO4 over other lithium batteries?
LiFePO4 batteries offer 2,000–5,000 cycles at 80% DoD vs. 500–1,000 for lead-acid. They maintain stable voltage under load, crucial for inverters. Thermal runaway risks are 3–5× lower than NMC chemistries. Pro Tip: Pair with a 100A BMS for 48V systems to handle 70A continuous draw safely.
For example, a 48V 100Ah LiFePO4 pack weighs ~45kg—half the weight of equivalent lead-acid. Beyond chemistry, what about scalability? LiFePO4 allows parallel connections without cell balancing issues common in NMC. However, series configurations require matched internal resistance. Transitioning to cost, while upfront prices are higher, LiFePO4’s 10-year lifespan often beats lead-acid’s 2–3 years.
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FAQs
No—automotive batteries prioritize high CCA, not deep cycling. Use deep-cycle LiFePO4 rated for ≥80% DoD.
How long will a 100Ah 48V battery last?
At 3000W: ~1 hour (100Ah × 48V × 0.8 DoD = 3,840Wh ÷ 3,000W). Add more batteries for extended runtime.
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