How Long Will A 100Ah Lithium Battery Typically Last?
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A 100Ah lithium battery typically lasts between 10 to 20 hours under a 5-10A load, depending on factors like discharge depth, temperature, and device efficiency. For instance, a 100Ah LiFePO4 battery supporting a 10A load provides ~10 hours at full discharge but closer to 8-9 hours when limited to 80% depth of discharge (DoD) for longevity. Real-world runtime may drop by 15-30% due to inefficiencies.
What Are Battery Amp Hours (Ah) & How They Affect CapacityWhat determines the runtime of a 100Ah lithium battery?
Runtime hinges on load current, discharge depth (DoD), and battery chemistry. Using the formula Runtime = Capacity (Ah) / Load (A), a 5A device draws ~20 hours at 100% DoD or ~16 hours at 80% DoD. LiFePO4 cells maintain stable voltage for longer runtime compared to lead-acid.
Technically, lithium batteries’ discharge curves are flatter, retaining usable voltage until ~90% depletion. Pro Tip: Avoid full discharges—limiting DoD to 80% extends cycle life by 2-3x. For example, a 100Ah LiFePO4 battery powering a 12V RV fridge (average 8A draw) lasts ~12.5 hours (100Ah ÷ 8A = 12.5h), reducing to ~10 hours with 80% DoD. High ambient temperatures (>35°C) accelerate degradation, while cold (<0°C) temporarily lowers capacity by 20-30%.
| Load (A) | 100% DoD Runtime | 80% DoD Runtime |
|---|---|---|
| 5 | 20h | 16h |
| 10 | 10h | 8h |
| 20 | 5h | 4h |
How does temperature affect a 100Ah lithium battery’s performance?
Extreme heat or cold reduces efficiency. At -10°C, capacity drops ~30% temporarily, while >40°C environments accelerate aging by 50%.
Lithium batteries operate optimally between 15-25°C. Cold temperatures slow ion movement, causing voltage sag—producing 70-80% of rated capacity until warmed. Pro Tip: Insulate batteries in sub-zero climates but avoid overheating. For example, a solar setup in a desert (45°C daytime) might see a 100Ah battery degrade to 70Ah within 2 years. Conversely, consistent 20°C storage preserves 95% capacity after 5 years.
Why does discharge depth (DoD) matter for lifespan?
Shallow discharges reduce stress. A 100Ah battery cycled at 50% DoD (50Ah used) achieves ~4,000 cycles, versus 1,500 cycles at 100% DoD.
Depth of discharge directly impacts cycle life due to electrode expansion/contraction. LiFePO4 cells tolerate deeper discharges (up to 90% DoD) but perform best at ≤80%. Think of DoD like bending a paperclip—each full discharge “bends” the battery slightly, weakening it over time. Pro Tip: Use a battery monitor to track DoD and avoid cycles below 20% state of charge (SoC).
| DoD | Cycle Life (LiFePO4) | Effective Capacity |
|---|---|---|
| 100% | 1,500–2,000 | 100Ah |
| 80% | 3,000–3,500 | 80Ah |
| 50% | 4,000–5,000 | 50Ah |
How do high-power applications shorten runtime?
Peak loads drain batteries faster. A 100Ah pack powering a 1,200W inverter (100A draw) lasts ~45 minutes at 80% DoD versus 10 hours for 100W loads.
High current draws induce voltage drops, triggering premature low-voltage cutoffs. For instance, an electric trolling motor drawing 30A reduces runtime to ~2.6 hours (100Ah ÷ 30A = 3.33h; 80% DoD = 2.66h). Pro Tip: Parallel batteries for high-drain devices—two 100Ah units in parallel provide 200Ah, doubling runtime while halving per-battery stress.
How to Charge Two Batteries in Parallel – Safety & Best PracticesABKPower Expert Insight
FAQs
No—real-world output is ~92-95Ah due to conversion losses. High loads or low temperatures further reduce usable capacity.
Can I mix old and new 100Ah batteries?No—capacity mismatches cause imbalance. Even identical models degrade differently over time, risking overcharge/overdischarge in parallel setups.