Ultimate Guide to LiFePO4 Voltage Chart

LiFePO4 (lithium iron phosphate) batteries have gained popularity as an alternative for charging appliances in the last few years. Because of these batteries’ extended lifespan, enhanced safety features, high energy density, and other qualities, solar generators use them.

By being able to read the LiFePO4 voltage chart, you can keep an eye on the battery’s performance and make sure it operates safely.

What is LiFePO4 Battery Voltage

One of the most widely used and secure batteries in solar systems is LiFePO4. They require little to no maintenance and have an incredibly long lifespan.

The voltage of the LiFePO4 battery is typically determined by its level of charge. But because of the non-linear nature of the LiFePO4 voltage chart, a small variation in SoC can result in a large voltage change.

What is LiFePO4 Voltage Chart

The level of charge of a single cell at various voltages, such as 12V, 24V, and 48V, is represented on the lithium iron phosphate (LiFePO4) battery voltage chart (often expressed as a percentage).

Percentage (SOC) 1 Cell 12V 24V 48V
100% Charging 3.65 14.6 29.2 58.4
100% Rest 3.40 13.6 27.2 54.4
90% 3.35 13.4 26.8 53.6
80% 3.32 13.3 26.6 53.1
70% 3.30 13.2 26.4 52.8
60% 3.27 13.1 26.1 52.3
50% 3.26 13.0 26.1 52.2
40% 3.25 13.0 26.0 52.0
30% 3.22 12.9 25.8 51.5
20% 3.20 12.8 25.6 51.2
10% 3.00 12.0 24.0 48.0
0% 2.50 10.0 20.0 40.0

A single LiFePO4 battery normally has a nominal voltage of 3.2V. At 3.65V, the cells are fully charged; at 2.5V, they are entirely discharged.

A fantastic substitute for 12V lead acid batteries are 12V 100Ah LiFePO4 batteries. These are among the safest solar off-grid system batteries. The battery voltage drops to 14.6V when they are completely charged. When completely discharged, it reduces to 10 volts. The voltage drops in relation to battery capacity are shown in the 12V LiFePO4 battery voltage chart below.

Either buy two identical 12V LiFePO4 batteries and link them in series, or buy a 24V LiFePO4 battery. When these batteries discharge to 20 volts, they are fully charged at 29.2 volts.

Larger solar power systems often employ 48V batteries. By maintaining a low amperage, the high-voltage solar system helps you save a lot of money on wiring and equipment.

LiFePO4 Battery Charging & Discharging

The remaining capacity that can be discharged above the entire capacity of the battery pack is indicated by the battery’s SoC (state of charge). Assume you have a 100Ah battery pack with 30Ah remaining for discharge. The SoC in this instance will be 30%.

Put differently, the battery will retain 30Ah even if it is charged to 100Ah and then discharged to about 70Ah. A battery’s voltage affects its SoC and vice versa. The voltage rises when the battery gets charged.

The correlation between the two factors may be seen in the SoC and LiFePO4 battery voltage chart that follows.

SOC (100%) Voltage (V)
100 3.60-3.65
90 3.50-3.55
80 3.45-3.50
70 3.40-3.45
60 3.35-3.40
50 3.30-3.35
40 3.25-3.30
30 3.20-3.25
20 3.10-3.20
10 2.90-3.00
0 2.00-2.50

The charge curve’s current state

The charge curve’s state shows how the voltage of a 1-cell battery changes with charging time.

Charging parameters for LiFePO4 batteries

Basic LiFePO4 battery charging parameters include nominal, maximum/minimum, charging, and float voltages, among other voltage kinds. The battery charging characteristics at 3.2V, 12V, 24V, and 48V are shown in the table below.

Characteristics 3.2V 12V 24V 48V
Charging Voltage 3.5~3.65V 14.2~14.6V 28.4V~29.2V 56.8V~58.4V
Float Voltage 3.2V 13.6V 27.2V 54.4V
Maximum Voltage 3.65V 14.6V 29.2V 58.4V
Minimum Voltage 2.5V 10V 20V 40V
Nominal Voltage 3.2V 12V/12.8V 24V/25.6V 48V/51.2V

LiFePO4 Float, Bulk, and Equalize Voltage

It’s crucial to remember that lithium can only be charged in bulk. The LiFePO4 battery turns off after it is fully charged.

Bulk, float, and equalize are the three voltage types that are most frequently seen.

 

Bulk Voltage: This voltage allows for a quicker charge of the battery. It commonly happens when the battery is fully discharged during the first phase of charging. A 12-volt LiFePO4 battery has a bulk voltage of 14.6 volts.

 

Float voltage: After the battery is fully charged, it is kept at a voltage that is typically lower than bulk voltage. A 12-volt LiFePO4 battery has a float voltage of 13.5 volts.

Equalize Voltage: Equalization is an important process that must be performed regularly to maintain the battery capacity. The 12-volt LiFePO4 battery’s equalized voltage is 14.6V.

Types 3.2V 12V 24V 48V
Bulk 3.65V 14.6V 29.2V 58.4V
Float 3.375V 13.5V 27.0V 54.0V
Equalize 3.65V 14.6V 29.2V 58.4V

Battery Discharge Curve

Discharge is the process of taking electricity out of the battery to charge devices. The link between voltage and discharge time is usually shown on the battery discharge chart.

The 12V LiFePO4 discharge curve at various discharge rates is shown below.

How to Check LiFePO4 Battery Capacity

One of the greatest ways to protect and extend the life of a LiFePO4 battery is to check its capacity. The three easy ways to check if the capacity is being completely depleted are listed below.

Method 1: Use a multimeter to check

Using a multimeter to check the open circuit battery voltage has a moderate level of accuracy. There is one drawback, though. All loads and charges must be unplugged, and the battery must be kept at rest.

The loads and chargers connected to the LiFePO4 battery must be taken out first. Before using the multimeter to measure the open circuit voltage, wait 15 to 30 minutes. You can contrast it with the voltage curve chart or the SoC chart found in your battery documentation.

Method 2: Use a Battery Monitor

This is one of the most accessible and reliable methods to measure battery capacity. All you need to do is connect a high-quality battery monitor to the battery and determine the charge level.

Method 3: Use a Solar Charge Controller

Using the solar charge controller to determine the battery capacity may seem convenient, but it is not a very accurate method. The voltage reading is mainly inaccurate as the measurement is done with loads and chargers attached.

LiFePO4 Voltage Chart FAQs

What effects of voltage will influence the LiFePO4 battery performance?

Voltage affects the LiFePO4 performance by altering the power it delivers, the energy it stores, and the overall lifespan.

  • Capacity:Battery voltage and capacity are directly proportional to each other. This means the voltage increase can increase the battery capacity.
  • Charging: The low charging voltage can reduce the battery capacity. On the other hand, the high charging voltage can lead to overcharging and damage.
  • Discharged:When the LiFePO4 battery is discharged below its recommended level, it reduces its capacity and lifespan.
  • Efficiency: A battery with higher voltage is generally more efficient in supplying more power to the appliances.

How to increase the LiFePO4 battery lifespan?

One of the simple methods to boost the lifespan or charging/discharging rates is by increasing the battery’s Ah capacity. The nylon tape around the cells and keeping the battery at a cool temperature can also improve the lifespan.

Voltage Capacity Charge Cycles Lifespan (Above 80% Original Capacity)
(V) (Ah %) (If charged and discharged to each of these voltages every day) (Charged once a day)
14.4V 100% 3200 cycles 9 years
13.6V 100% 3200 cycles 9 years
13.4V 99% 3200 cycles 9 years
13.3V 90% 4500 cycles 12.5 years
13.2V 70% 8000 cycles 20 years
13.1V 40% 8000 cycles 20 years
13.0V 30% 8000 cycles 20 years
12.9V 20% 8000 cycles 20 years
12.8V 17% 6000 cycles 16.5 years
12.5V 14% 4500 cycles 12.5 years
12.0V 9% 4500 cycles 12.5 years
10.0V 0% 3200 cycles 9 years

What is the minimum voltage damage for LiFePO4?

For 12V LiFePO4 batteries, the minimum voltage damage is approximately 10V. The LiFePO4 battery is likely to suffer irreversible damage if it is discharged below the minimum voltage. Because of this, it’s imperative that you make sure you charge your LiFePO4 batteries safely by using the voltage chart.

Final Thoughts

LiFePO4 batteries are the most economical in the long run, despite not being the cheapest or most accessible option. The LiFePO4 voltage chart makes it easy to determine the battery’s state of charge.