Lithium Battery Voltage Guide
Estimate the approximate state of charge (SOC) of a 12V LiFePO4 battery based on resting voltage.
IMPORTANT: Voltage readings are only approximate. For best accuracy:
- Let the battery rest with no charging or loads for 20–30 minutes.
- Do not measure while solar is charging.
- Do not measure while heavy loads are running.
- A shunt-based battery monitor is far more accurate than voltage alone.
Important: Voltage Sag Under Load
A battery may read higher at rest and lower when an appliance such as a fridge starts running. For example, a lithium battery might read 13.2V at rest, then drop to 12.8V when the fridge compressor turns on. This does not mean the battery has suddenly lost a large amount of charge.
For a better estimate, measure voltage after the battery has rested with no charging and no loads for 20–30 minutes.
Typical LiFePO4 Resting Voltages
| Voltage | Approx Charge |
|---|---|
| 13.5V | 100% |
| 13.3V | 90% |
| 13.2V | 70–80% |
| 13.1V | 50–60% |
| 12.9V | 30–40% |
| 12.8V | 20–30% |
| 12.5V | Very Low |
More Tiny Camper Tools
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- Camping Battery Calculator — Estimate battery runtime and daily power usage.
- Solar Recovery Calculator — Estimate how long solar may take to replace used power.
- Battery Voltage Guide — Understand lithium battery voltage and voltage sag.
- Trip Cost Calculator — Estimate fuel, camping and travel costs.
- Back to Tiny Camper's Toolbox
Results are estimates only and should be used as general guides. Actual camping performance depends on weather, equipment, battery condition and real-world usage.
