LiFePO4 Voltage Chart: State of Charge for 3.2 V, 12 V, 24 V and 48 V

How this is calculated

Two steps. The reading is pulled back to what the pack would show at rest — add current times internal resistance when discharging, subtract when charging — then divided by the cells in series and looked up on the chemistry's curve.

Worked example. A 12 V LiFePO4 bank reads 13.12 V while a 100 A inverter load runs, and the datasheet gives 0.8 mΩ. The sag is 100 × 0.0008 = 0.08 V, so the resting equivalent is 13.20 V, or 3.300 V across four cells. That lands on 60 percent.

Now the part that matters. A Fluke 117 is specified to ±(0.5% of reading + 2 counts), which at 13.20 V is ±0.086 V. Put 13.114 V and 13.286 V through the same lookup and the answer runs from about 38 percent to about 82 percent. The meter is working perfectly; the chemistry simply refuses to say more.

Quick answers

What voltage is a fully charged 12 V LiFePO4 battery?

About 13.4 to 13.6 V once it has been off the charger for a couple of hours. While charging it sits far higher: Victron specifies 14.2 V absorption and 13.5 V float for a 12.8 V battery.

Why does 13.2 V not tell me the state of charge?

The plateau from 20 to 90 percent is only 0.32 V wide, and a Fluke 117 is specified to ±0.086 V there. Those two numbers put 13.2 V anywhere between 38 and 82 percent charge before drift or cell-to-cell spread is counted.

What is the low temperature charge cut-off?

The EVE and CATL cell datasheets give 0 °C (32 °F) as the minimum charging temperature. Victron sets its own window at +5 °C and states that going below that voids the warranty.

Is a shunt better than a voltmeter?

Yes. A shunt counts amp-hours in and out, the quantity that actually changes. Battery University notes that roughly 80 percent of a LiFePO4 cell's stored energy sits inside the flat part of the curve.

How much does load pull the voltage down?

Victron lists 0.8 mΩ for its 12.8 V 100 Ah and 200 Ah batteries, so 100 A moves the reading about 0.08 V — small in volts, and a quarter of the whole plateau.

Why the flat curve defeats a voltmeter

Lead-acid voltage falls steadily as the electrolyte weakens, which is why reading a bank with a meter worked well enough for a century. Lithium iron phosphate holds close to 3.3 V per cell across most of its usable range and breaks away only at the very top and the very bottom.

Battery University puts the consequence plainly: about 80 percent of the stored energy sits inside that flat profile, so a reading tells you full and low and nothing in between.

That tolerance bar is a laboratory-grade handheld working to its published specification, and it still covers more than half the LiFePO4 band. A cheap meter, a long lead or a pack that came off charge ten minutes ago all widen it further.

Charge, absorption and float setpoints

These go into the charge controller or inverter-charger. Your own battery manual outranks any generic chart, so set from that and use this to check it.

Setting	Per cell	12 V	24 V	48 V
Cell charge cut-off (EVE, CATL)	3.65 V	14.60 V	29.20 V	58.40 V
Absorption, Victron recommended	3.55 V	14.20 V	28.40 V	56.80 V
Absorption, Victron allowed range	3.50–3.60 V	14.0–14.4 V	28.0–28.8 V	56.0–57.6 V
Float	3.375 V	13.50 V	27.00 V	54.00 V
BMS stops charging above	3.75 V	15.00 V	30.00 V	60.00 V
BMS pre-alarm below	3.10 V	12.40 V	24.80 V	49.60 V
End of discharge	2.80 V	11.20 V	22.40 V	44.80 V
Cell datasheet discharge cut-off	2.50 V	10.00 V	20.00 V	40.00 V

Absorption, float, pre-alarm and end-of-discharge rows from the Victron Lithium Battery Smart datasheet; cell cut-off rows from the EVE LF280K specification version B (March 2021) and the CATL 314Ah specification.

Victron asks for at least two hours a month at absorption on a lightly cycled system, so the cell balancers have time to work, and four to eight hours a month on an off-grid bank. That is why a system parked at float all winter drifts out of balance.

Cold weather is the real limit

Charging a cold lithium iron phosphate cell plates metallic lithium onto the anode. The damage is permanent and gives no warning, which is why the charge window is narrower than the discharge window on every datasheet, and why Victron sets its own floor at +5 °C rather than the cell makers’ 0 °C and voids the warranty below it.

Limit	Celsius	Fahrenheit	Source
Charging, cell datasheet	0 to +55	32 to 131	EVE LF280K
Charging, cell datasheet	0 to +60	32 to 140	CATL 314Ah
Charging, battery maker	+5 to +50	41 to 122	Victron Lithium Smart
Discharging	−20 to +50	−4 to 122	Victron Lithium Smart
Discharging, cell datasheet	−20 to +55	−4 to 131	EVE LF280K
Storage, long term	0 to +35	32 to 95	EVE LF280K

Cold costs capacity too. Victron rates a 12.8 V 200 Ah battery at 160 Ah at 0 °C and 100 Ah at −20 °C, half the nameplate. Size for the coldest week; the off-grid battery bank calculator takes that derating as an input.

How LiFePO4, NMC and lead-acid compare

	LiFePO4	NMC	Flooded lead-acid
Nominal per cell	3.20–3.30 V	3.60–3.70 V	2.00 V
Charge limit	3.65 V	4.20 V	2.35–2.45 V absorption
Operating range	2.5–3.65 V	3.0–4.2 V	1.92–2.12 V at rest
Cycle life	2,000 and higher	1,000–2,000	Depends on depth of discharge
Thermal runaway onset	270 °C	210 °C	Not applicable
Voltage as a fuel gauge	Poor	Workable	Good

Chemistry rows from Battery University BU-205; lead-acid voltages from the Trojan Battery user guide.

NMC sloped voltage is why phones show a believable percentage without a shunt, and its lower runaway threshold is why most fixed storage moved to iron phosphate. The trade is set out in the LiFePO4 against NMC comparison.

What a shunt gives you that a meter cannot

A shunt is a precise low-value resistor in the negative battery cable. The monitor reads the tiny voltage across it, converts that to current, and adds up amp-hours in and out.

• It reads correctly under load, so the bank can be checked at seven in the evening rather than in the morning.
• It gives time remaining at the present draw, the number you act on.
• It logs each day's deepest discharge, which sets how long the pack lasts.
• It still needs an occasional full charge to resynchronize, the one job the voltage reading keeps.

Two habits go with it: read at the battery terminals rather than the far end of a cable run, and give the pack two hours off charge and off load before trusting a resting figure. The top table assumes both.

Sources

EVE Power LF280K product specification, version B, effective 23 March 2021. CATL 3.2 V 314 Ah cell specification for energy storage. Victron Energy 12.8 & 25.6 Volt Lithium-Iron-Phosphate Batteries Smart datasheet, and the Lithium Battery Smart manual sections on operation and technical data, revisions current at September 2026. Trojan Battery user guide, Table 7. Battery University BU-903 on measuring state of charge and BU-205 on lithium-ion types. Fluke 114/115/116/117 detailed specifications, direct-current volts, ±(0.5% of reading + 2 counts) on the 6 V, 60 V and 600 V ranges. Figures checked September 2026.

Go deeper

Turn a reading into a bank size with the off-grid battery bank calculator, which applies the cold derating above. The LiFePO4 against lead-acid sizing guide covers what the flat curve costs over a decade, and the inverter-charger sizing guide handles these setpoints from the charger side. The rest sits in the storage section.