13.6V
100% (Resting)
13.0V
30% SoC
10.0V
0% (Cutoff)
Every LiFePO4 battery owner needs a voltage chart. It's the fastest way to get a rough idea of how much charge is left - pull out a multimeter, check the voltage, and look it up.
But LiFePO4 batteries have a quirk that trips people up: the voltage curve is almost flat for most of the discharge cycle. This guide gives you the chart, explains why it's tricky, and shows you how to actually get accurate state-of-charge readings.
01
12V LiFePO4 Voltage Chart (Resting)
This chart shows the open circuit voltage (resting voltage) for a 12V LiFePO4 battery at each state of charge level. All measurements assume the battery has been disconnected from loads and chargers for at least 15-30 minutes.
| Voltage | SoC | Status |
|---|---|---|
| 14.6V | 100% | Charging |
| 13.6V | 100% | Full |
| 13.4V | 99% | Full |
| 13.3V | 90% | Good |
| 13.2V | 70% | Good |
| 13.1V | 40% | OK |
| 13.0V | 30% | Low |
| 12.9V | 20% | Low |
| 12.8V | 17% | Critical |
| 12.0V | 9% | Critical |
| 10.0V | 0% | Empty |
02
3.2V Single-Cell LiFePO4 Voltage Chart
Every LiFePO4 pack is built from 3.2V cells wired in series. Knowing the per-cell voltage lets you work with any pack size: multiply by 4 for 12V, 8 for 24V, or 16 for 48V.
| SoC% | Cell Voltage (3.2V nom.) |
|---|---|
| 100% (charging) | 3.65V |
| 100% (resting) | 3.40V |
| 90% | 3.35V |
| 80% | 3.32V |
| 70% | 3.30V |
| 60% | 3.27V |
| 50% | 3.26V |
| 40% | 3.25V |
| 30% | 3.22V |
| 20% | 3.20V |
| 10% | 3.00V |
| 0% | 2.50V |
03
The Flat Curve Problem (And What to Do About It)
Here's the thing most voltage charts don't explain: look at the chart above and notice how the voltage barely changes from 90% to 40% SoC. The difference between 13.3V and 13.1V is just 0.2V - but it represents 50% of your battery capacity.
This flat discharge curve is a feature of LiFePO4 chemistry. It means your devices get stable, consistent power throughout most of the discharge. But it also means voltage is nearly useless for estimating SoC in the 20-90% range.
What 0.1V Really Means
A cheap multimeter accurate to ±0.1V is basically useless in this range. You'd need ±0.01V precision to tell 70% from 40%.
Three Ways to Get Accurate SoC
Shunt-Based Battery Monitor (Best)
A coulomb counter like the Victron SmartShunt or Renogy 500A monitor tracks every amp in and out of your battery. It calculates true SoC regardless of voltage. This is the only reliable method for LiFePO4. Costs $50-100.
Built-In BMS with Bluetooth
Many newer LiFePO4 batteries (LiTime, SOK, Redodo) have a built-in BMS with a smartphone app. The BMS tracks SoC internally and reports it via Bluetooth. Accuracy varies by brand, but it's much better than voltage alone.
Voltage at the Extremes Only
Voltage is actually useful at the top and bottom of the curve. Above 13.4V you know you're above 90%. Below 12.9V you know you're below 20%. In between, treat the reading as "somewhere in the middle" and don't try to guess exact percentages.
04
24V and 48V LiFePO4 Voltage Charts
Larger systems use 24V or 48V configurations. The SoC percentages are the same - just multiply the per-cell voltages by 8 (for 24V) or 16 (for 48V).
24V LiFePO4 (8 cells in series)
| Voltage | SoC | Status |
|---|---|---|
| 29.2V | 100% (charging) | Charging |
| 27.2V | 100% (resting) | Full |
| 26.6V | 90% | Good |
| 26.4V | 70% | Good |
| 26.2V | 40% | OK |
| 26.0V | 30% | Low |
| 25.6V | 17% | Critical |
| 20.0V | 0% | Empty |
48V LiFePO4 (16 cells in series)
| Voltage | SoC | Status |
|---|---|---|
| 58.4V | 100% (charging) | Charging |
| 54.4V | 100% (resting) | Full |
| 53.2V | 90% | Good |
| 52.8V | 70% | Good |
| 52.4V | 40% | OK |
| 52.0V | 30% | Low |
| 51.2V | 17% | Critical |
| 40.0V | 0% | Empty |
05
Cycle Life vs Depth of Discharge
How deep you discharge your LiFePO4 battery each day has a massive impact on how long it lasts. Shallower cycles mean exponentially more total cycles before the battery degrades.
| Depth of Discharge | Estimated Cycles | Years (Daily Use) |
|---|---|---|
| 100% DoD | ~3,000 | ~8 years |
| 80% DoD | ~4,500 | ~12 years |
| 50% DoD | ~8,000 | ~22 years |
| 30% DoD | ~10,000+ | ~27+ years |
06
How to Measure LiFePO4 Voltage Accurately
Getting an accurate voltage reading requires the right conditions. Here's the correct procedure:
Disconnect Everything
Turn off all loads (inverter, fridge, lights). Disconnect your solar charge controller. The battery must have zero current flowing in or out.
Wait 15-30 Minutes
The battery needs time to settle. After heavy discharge or charging, the voltage will drift for several minutes. 15 minutes is the minimum; 30 minutes gives a more accurate reading. For precision testing, wait 2-4 hours.
Measure at the Battery Terminals
Place your multimeter probes directly on the battery terminal posts, not on cable lugs or fuse holders. Set your multimeter to DC voltage. You need at least 0.01V resolution (two decimal places) for this to be useful.
Compare to the Chart
Match your reading to the chart above. Remember: if you're in the 13.1-13.3V range, the best you can say is "somewhere between 40-90%." That's the flat zone and voltage won't tell you more than that.
07
LiFePO4 vs Lead-Acid Voltage: Don't Mix Them Up
If you're switching from lead-acid to LiFePO4, throw out your old voltage assumptions. The same voltage reading means very different things for each chemistry. For a full breakdown of the differences beyond voltage, see our LiFePO4 vs AGM comparison.
| Feature | 12V LiFePO4 | 12V Lead-Acid (AGM) |
|---|---|---|
| Full (resting) | 13.6V | 12.73V |
| 90% SoC | 13.3V | 12.62V |
| 70% SoC | 13.2V | 12.32V |
| 50% SoC | 13.15V | 12.10V |
| 30% SoC | 13.0V | 11.81V |
| 0% (empty) | 10.0V | 10.5V |
| Nominal voltage | 12.8V | 12.0V |
| Voltage curve shape | Flat (hard to read) | Sloped (easy to read) |
08
LiFePO4 Charging Parameters by Voltage
When setting up your charge controller or charger for LiFePO4, use these parameters. If your controller has a "Lithium" preset, use it. If not, manually enter these values:
| Parameter | 12V | 24V | 48V |
|---|---|---|---|
| Bulk/Absorb voltage | 14.2-14.6V | 28.4-29.2V | 56.8-58.4V |
| Float voltage | 13.6V | 27.2V | 54.4V |
| Low-voltage cutoff | 12.0V | 24.0V | 48.0V |
| Absorption time | 0-30 min | 0-30 min | 0-30 min |
| Equalization | Disabled | Disabled | Disabled |
09
CC/CV Charging Stages Explained
LiFePO4 batteries charge using a two-stage process called CC/CV (Constant Current / Constant Voltage). Understanding these stages helps you set up your charger correctly and know what your battery is doing at each point.
Stage 1: Bulk / Constant Current (CC)
The charger pushes its maximum rated current into the battery while the voltage gradually rises toward 14.2-14.6V (for 12V). This is the fastest phase and gets the battery to roughly 90-95% SoC. Most of the charging time is spent here.
Stage 2: Absorption / Constant Voltage (CV)
Once voltage hits the target (14.6V), the charger holds voltage constant while current tapers down. The battery slowly fills from ~90% to 100%. This stage is shorter for LiFePO4 than lead-acid (typically 0-30 minutes vs. 2-4 hours). Some chargers skip this stage entirely for LiFePO4.
Float: Not Needed for LiFePO4
LiFePO4 batteries have very low self-discharge (about 2% per month), so they don't need a float charge to stay topped off like lead-acid batteries do. If your charger forces a float stage, set it to 13.5-13.6V. This keeps the battery full without stressing the cells.
10
Frequently Asked Questions
What voltage is a fully charged 12V LiFePO4 battery?
A fully charged 12V LiFePO4 battery reads 14.6V while charging. Once removed from the charger and rested for 15-30 minutes, it settles to 13.4-13.6V. This resting voltage is the true "full" reading. Do not expect to see 14.6V without a charger connected.
What voltage is a dead LiFePO4 battery?
A 12V LiFePO4 battery is considered empty at 10V (2.5V per cell). However, you should never let it get that low. The built-in BMS will disconnect at 10V to protect the cells. Set your low-voltage cutoff to 12.0V (about 9% SoC) to preserve battery lifespan.
Why does my LiFePO4 battery voltage stay the same?
LiFePO4 chemistry has an extremely flat discharge curve between 20-90% SoC. The voltage only changes by about 0.4V across this entire range (13.0V to 13.4V for a 12V battery). This is normal and actually a feature - it means stable power output. Use a shunt-based battery monitor for accurate SoC readings in this range.
Can I use a lead-acid voltage chart for LiFePO4?
No. Lead-acid and LiFePO4 have completely different voltage curves. A lead-acid battery at 12.4V is about 50% charged, but a LiFePO4 battery at 12.4V is nearly empty (about 14%). Using the wrong chart will give dangerously inaccurate readings. Always use a LiFePO4-specific chart.
How long should a LiFePO4 battery rest before measuring voltage?
Wait at least 15-30 minutes after disconnecting all loads and chargers. Some manufacturers recommend up to 2-4 hours for the most accurate reading. The voltage needs time to stabilize - a battery under load reads lower, and one just off the charger reads higher than the true resting voltage.
What is the nominal voltage of a 12V LiFePO4 battery?
12.8V, which is 4 cells in series at 3.2V per cell. This is higher than the 12.0V nominal of lead-acid batteries, which is why LiFePO4 delivers more usable energy at the same Ah rating.
What is the best float voltage for a 12V LiFePO4?
13.5-13.6V, but LiFePO4 doesn't truly need float charge. Its low self-discharge (about 2% per month) means float mainly keeps the battery topped off for connected loads, not to prevent sulfation like lead-acid. If your charger forces a float stage, set it to 13.5-13.6V to avoid unnecessary stress on the cells.
How can I tell if my LiFePO4 battery is going bad?
Signs include reduced runtime despite a full charge, longer charge times than usual, cell voltage imbalance greater than 0.1V between cells, and physical swelling of the battery case. Use a battery monitor to track capacity loss over time. You should expect about 80% of original capacity remaining after 2,000-3,000 full cycles.
Does discharge rate affect LiFePO4 voltage readings?
Yes. A battery discharged at 1C (high current) reads lower voltage than one discharged at 0.2C (low current) at the same state of charge. For accurate SoC readings, always measure open-circuit voltage after letting the battery rest for 10-15 minutes with no load connected.
What is the low voltage cutoff for a 12V LiFePO4?
Most BMS units disconnect at 10.0-10.5V (2.5V per cell) to prevent permanent cell damage. Some quality BMS units have a recovery voltage set slightly higher than the cutoff. Never repeatedly discharge to the BMS cutoff point — it stresses the cells and shortens overall lifespan. Set your inverter or load cutoff to 12.0V for best longevity.
Sources
- Voltage data: Based on EVE LF280K cell datasheets and corroborated against Footprint Hero, Clever Solar Power, and DIY Solar Forum community measurements
- Charging parameters: Victron Energy MPPT Solar Charger manual and Battle Born Batteries charging guide
- Lead-acid comparison: Trojan Battery Company voltage charts for flooded and AGM batteries
This content is for informational and planning purposes only. Always consult a licensed electrician or qualified professional before making electrical installations or purchasing decisions. See our terms of use.