This question has two answers — and most people confuse them:
- Runtime — How long it runs your devices on a single charge
- Lifespan — How many years before the battery degrades
Both matter. Let's cover each.
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Part 1: Runtime (Hours Per Charge)
The Formula
Runtime (hours) = Battery Capacity (Wh) × DOD × Inverter Efficiency ÷ Device Watts
Where:
- •DOD = Depth of Discharge (0.80 for LiFePO4, 0.70 for Li-ion)
- •Inverter Efficiency = 0.85 (15% loss converting DC to AC)
Examples
1000 Wh LiFePO4 station running a 100W device:1000 × 0.80 × 0.85 ÷ 100 = 6.8 hours
500 × 0.80 × 0.85 ÷ 20 = 17 hours
2000 × 0.80 × 0.85 ÷ 60 = 22.7 hours
Quick Runtime Table
| Battery (Wh) | Phone (20W) | Laptop (65W) | Mini Fridge (60W) | TV (80W) | Microwave (1000W) |
|---|---|---|---|---|---|
| 300 Wh | 10h | 3h | 3.4h | 2.5h | 0.25h (15 min) |
| 500 Wh | 17h | 5.2h | 5.7h | 4.3h | 0.4h (24 min) |
| 1000 Wh | 34h | 10.5h | 11.3h | 8.5h | 0.85h (51 min) |
| 2000 Wh | 68h | 20.9h | 22.7h | 17h | 1.7h |
| 3000 Wh | 102h | 31.4h | 34h | 25.5h | 2.55h |
*Based on LiFePO4 (80% DOD) with 85% inverter efficiency.*
Tips to Maximize Runtime
- Use DC output when possible — Skips the inverter, gains 10-15% runtime
- Turn off unnecessary features — Display backlight, Bluetooth, LED indicators
- Avoid running devices at max draw — A laptop on battery saver uses 30W vs 65W
- Don't let it run to 0% — Stop at 10-20% to protect battery health
- Keep it cool — Batteries are less efficient when hot
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Part 2: Lifespan (Years of Use)
What Determines Lifespan
Battery lifespan is measured in cycle life — the number of full charge/discharge cycles before capacity drops to 80% of original.
| Battery Type | Typical Cycle Life | At Daily Use | At Weekly Use |
|---|---|---|---|
| LiFePO4 | 3,000–6,500 | 8–17 years | 57–125 years* |
| Li-ion (NMC) | 500–1,000 | 1.4–2.7 years | 10–19 years |
*Effectively unlimited for occasional users.
What Kills Batteries Faster
- Heat — Storing/using above 40°C accelerates degradation
- Full charge storage — Keeping at 100% for months stresses cells
- Deep discharge — Regularly draining to 0% shortens life
- Fast charging constantly — Generates heat; use slow charge when time allows
Optimal Storage Practices
| What to do | Why |
|---|---|
| Store at 60-80% charge | Least stress on cells |
| Store in cool place (15-25°C) | Heat is the #1 killer |
| Top off every 3-6 months | Prevents over-discharge during storage |
| Avoid leaving plugged in at 100% indefinitely | Some units handle this fine, some don't |
Real-World Lifespan Expectations
Camping use (50 cycles/year):- •LiFePO4 (3000 cycles): 60 years — will outlive the electronics inside
- •Li-ion (500 cycles): 10 years — still decent for occasional use
- •LiFePO4 (3000 cycles): 8.2 years
- •Li-ion (500 cycles): 1.4 years — unacceptable
- •Either chemistry: 25+ years — cycle life is irrelevant; calendar aging matters more
The Bottom Line
- •For occasional use (camping, emergency): Either chemistry lasts many years. Buy whatever's cheaper.
- •For daily use (RV, off-grid): LiFePO4 is the only rational choice.
- •For home backup (rare use): Either works, but LiFePO4 gives peace of mind.
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Calculate Your Specific Runtime
Don't want to do the math? Our Power Calculator computes exact runtime for any combination of appliances, with your specific power station's capacity.
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