LINEX

LiFePO4 Battery Voltage Charts: 12V, 24V and 48V

Short answer: A 12V LiFePO4 battery rests at about 13.6V when full and 12.8V at roughly 20% state of charge; a 24V pack doubles those figures and a 48V pack quadruples them. Charging voltages are higher than rest voltages — typically 14.2–14.6V for a 12V pack — and the exact values depend on the BMS and cell configuration.

A voltage chart is the quickest way to estimate state of charge, but only if you know whether you are reading a battery at rest or under load. This page gives the reference tables and the caveats that matter in practice.

State of Charge Chart (Rest Voltage)

Measure after the battery has rested for at least 30 minutes with no charge or discharge. Values are for a 4-cell 12V pack; multiply by 2 for 24V and by 4 for 48V.

State of charge	12V pack	24V pack	48V pack
100%	13.6V	27.2V	54.4V
90%	13.4V	26.8V	53.6V
80%	13.2V	26.4V	52.8V
50%	13.0V	26.0V	52.0V
20%	12.8V	25.6V	51.2V
10%	12.5V	25.0V	50.0V

LiFePO4 holds a very flat voltage curve between roughly 20% and 90%, which is why voltage alone cannot tell you the exact state of charge in that band. A shunt-based battery monitor is more accurate for daily use.

Charging Voltage Chart

Pack	Absorption / boost	Float
12V (4S)	14.2–14.6V	13.5–13.6V
24V (8S)	28.4–29.2V	27.0–27.2V
48V (16S)	56.8–58.4V	54.0–54.4V

These are common ranges, not universal settings. LINEX 48V telecom models, for example, specify a float charge of 51.0V and equalization at 53.3V because they are configured for rectifier-based site power. Always use the values in the model datasheet — a charger set for a 16S pack can overcharge a pack configured for 15S.

Rest Voltage vs Load Voltage

Under load, a LiFePO4 pack reads lower than its rest voltage, and the gap grows with current. A 12V 100Ah battery pulling 100A can drop 0.5–1.0V below its rest value; the same battery at 10A barely moves. This is internal resistance, not lost capacity. If you measure while a load is connected, expect a lower number and do not use it to judge state of charge.

Low Temperature

Charging LiFePO4 below 0°C causes lithium plating and permanent damage. Most BMS units block charging below 0–5°C while still allowing discharge. Voltage also sags more in the cold, so a pack that reads 12.8V at 25°C may read lower at -10°C without any loss of capacity.

What Voltage Cannot Tell You

Remaining runtime — you need capacity in kWh and the load in watts.
Cell balance — a pack can read normal while one cell group drifts.
Health — an aged pack may still reach 13.6V but deliver far less energy.

Battery group sizes: for BCI group numbers, case dimensions in mm and inches, and drop-in replacement checks, see Battery Types & Sizes: A Buyer’s Guide.

Frequently asked questions

What voltage is a 12V LiFePO4 battery fully charged?

About 13.6V at rest after a full charge and a short rest. While charging it reads higher, typically 14.2–14.6V, and it settles back within an hour of the charger stopping.

Is 12.0V empty for a LiFePO4 battery?

Yes, 12.0V at rest is close to empty and 10.0V is the usual cut-off. Unlike lead-acid, discharging a LiFePO4 pack below 10V can trigger BMS protection and shorten life.

Why does my 48V battery read 51V when full?

51.2V is the nominal voltage of a 16S LiFePO4 pack, not its full-charge voltage. A full pack rests near 54.4V; 51.2V corresponds to roughly 20% state of charge. Some telecom packs are configured differently, so check the datasheet.

Can I use these charts for AGM or gel batteries?

No. Lead-acid rest voltages are different (12.7V full, 12.0V at 50%) and they tolerate different charging voltages. Using a LiFePO4 chart for lead-acid will overestimate state of charge.

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