Lithium iron phosphate voltage is very flat between about 20% and 90%, so read it at rest: no charging or loads for 30+ minutes. Under load or on charge it can read 0.2–0.5 V off. For accuracy, use a shunt battery monitor.
| SOC | 12V | 24V | 48V |
|---|---|---|---|
| 100% | 13.6 | 27.2 | 54.4 |
| 99% | 13.4 | 26.8 | 53.6 |
| 90% | 13.3 | 26.6 | 53.2 |
| 70% | 13.2 | 26.4 | 52.8 |
| 40% | 13.1 | 26.2 | 52.4 |
| 30% | 13.0 | 26.0 | 52.0 |
| 20% | 12.9 | 25.8 | 51.6 |
| 17% | 12.8 | 25.6 | 51.2 |
| 14% | 12.5 | 25.0 | 50.0 |
| 9% | 12.0 | 24.0 | 48.0 |
| 0% | 10.0 | 20.0 | 40.0 |
Values are typical for a rested pack; cells vary by brand and temperature. Your BMS normally cuts off near 10–10.5 V (12V pack) to protect the cells.
| SOC | Volts |
|---|---|
| 100% | 12.7 |
| 90% | 12.5 |
| 80% | 12.42 |
| 70% | 12.32 |
| 60% | 12.2 |
| 50% | 12.06 |
| 40% | 11.9 |
| 20% | 11.58 |
Lead-acid should not go below about 50% (≈12.06 V) regularly. That is why the battery bank calculator uses 50% usable for AGM and ~90% for lithium.
Safety: These are general estimates, not a design. Follow your equipment manufacturer's instructions and local electrical code, and consult a qualified electrician for anything connected to shore power, a house, or high-current batteries.
About 13.6 V at rest right after charging (14.2–14.6 V while charging). It settles to around 13.3–13.4 V after a few hours.
Roughly 13.1–13.2 V at rest. Because the curve is so flat, voltage is a poor gauge in the middle; a shunt monitor counts amp-hours instead.
Many users stop around 12.0 V (about 10% left) to leave a reserve; the BMS low-voltage cutoff is usually around 10–10.5 V.
Yes, multiply the 12V numbers by 2 for a 24V (8-cell) pack and by 4 for a 48V (16-cell) pack.
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