How long will a 100Ah lithium battery run an appliance that requires 400W?
A 100Ah lithium battery (12.8V nominal) can theoretically power a 400W appliance for 3.2 hours under ideal conditions. However, real-world factors like inverter efficiency losses (10–15%), depth of discharge limits (80% recommended for lifespan), and voltage sag reduce runtime to approximately 2–2.5 hours. Pro Tip: For continuous 400W loads, use a lithium battery with ≥150Ah capacity to account for efficiency losses and safety margins.
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What determines lithium battery runtime for high-wattage appliances?
Runtime hinges on energy capacity (Wh) and load efficiency. A 12.8V 100Ah LiFePO4 battery stores 1,280Wh (12.8V×100Ah). Divide this by the appliance’s wattage (400W) for theoretical runtime: 3.2 hours. Real-world variables like inverter conversion losses (85–90% efficiency) and BMS protections reduce usable energy by 15–25%.
Practically speaking, lithium batteries maintain voltage better than lead-acid during discharge, but their low internal resistance doesn’t eliminate efficiency losses in power conversion. For example, a 400W microwave running via a 90% efficient inverter pulls 444W (400W ÷ 0.9) from the battery—cutting runtime to ~2.9 hours before DoD limits. Pro Tip: Always derate battery capacity by 20% for cyclic applications to avoid premature aging.
How does voltage affect 100Ah battery performance?
Nominal voltage defines energy storage potential. A 12V 100Ah lead-acid battery holds 1,200Wh, while a 12.8V LiFePO4 version stores 1,280Wh—6.7% more energy. Higher voltage systems (24V/48V) reduce current draw, minimizing resistive losses in cables and connectors.
| Battery Type | Voltage | Usable Wh (80% DoD) |
|---|---|---|
| LiFePO4 | 12.8V | 1,024Wh |
| Lead-Acid | 12V | 720Wh |
For 400W loads, a 24V 100Ah LiFePO4 battery (2,560Wh) would last 5.1 hours theoretically—double a 12V system’s runtime. But what if your appliance only accepts 120V AC? You’ll need an inverter regardless, introducing ~10% loss. Pro Tip: Match battery voltage to your inverter’s DC input range to avoid boost/buck conversion penalties.
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FAQs
Yes—parallel connection doubles capacity to 200Ah, extending 400W runtime to ~4–5 hours. Ensure both batteries share identical voltage, age, and chemistry to prevent imbalance.
Do lithium batteries lose capacity over time with heavy loads?
All batteries degrade, but LiFePO4 retains ≥80% capacity after 2,000 cycles at 100% DoD. Avoid sustained loads above 0.5C (50A for 100Ah) to minimize heat-related aging.