LiFePO4 Cell Voltage Chart

The lithium iron phosphate battery (LiFePO4) uses lithium iron phosphate as the positive electrode material, graphite carbon as the negative electrode material, and metal as the negative electrode material. In addition to its low cost, high energy density, long cycle life, safety, and stability, it is widely used in electric vehicles, golf carts, forklifts, RVs, floor machines, scissor lifts, aerial work platforms, marine, airport handling, home storage, and industrial and commercial energy storage.

Basics of LiFePO4 Battery Voltage

Here are some basic definitions of LiFepo4 battery voltage.

Nominal Voltage – The battery's nominal voltage is 3.25V. Battery charging and discharging are monitored using the standard voltage.

Storage Voltage – 3.2V-3.4V If the battery won't be used for a long time, it needs to be stored at this voltage. Keeping the storage voltage high ensures that the battery does not lose capacity.

Fully Charged Voltage – The battery is charged to a maximum voltage of 3.65V. The battery may be irreparably damaged if it is charged above this level.

Discharge Voltage – Discharge voltages must be at least 2.5V. Discharging below this voltage is not recommended. Battery damage may occur if it is discharged beyond its limit.

Deep Discharge – There is an insufficient voltage in this case. LiFePO4 batteries can fail completely after deep discharge.

LiFePO4 voltmeter: 1 Cell 12V 24V 36V 48V 72V

3.2V LiFePO4 battery voltage meter

• Nominal voltage: 3.2V

• Charging voltage: 3.65V

• Discharge cut-off voltage: 2.5V

12V LiFePO4 battery voltage meter

• Nominal voltage:12.8V
• Charging voltage: 14.6V
• Discharge cut-off voltage: 10V

The 12 volt is ideal for electric bicycles,trolling motors,marine, aerial work platforms,RV,and home solar panels.

24V LiFePO4 battery voltage meter

• Nominal voltage:25.6V
• Charging voltage: 29.2V
• Discharge cut-off voltage: 20V

The 24V LiFePO4 batteries are perfect for boat trolling motors, scissor lifts, and boom lifts. The energy used by sweepers, floor machines, and RVs.
If you want to buy two identical 12V LiFePO4 batteries in series, you can buy a 24V LiFePO4 battery.

36V LiFePO4 battery voltage meter

• Nominal voltage:38.4V
• Charging voltage: 43.8V
• Discharge cut-off voltage: 30V

36 Volt LiFePO4 batteries are ideal for golf carts, community electric cars, UTVs, and ATVs

48V LiFePO4 battery voltage meter

• Nominal voltage:51.2V
• Charging voltage: 58.4V
• Discharge cut-off voltage: 40V

The 48V system is the best choice for home solar powerwalls, electric golf carts, and aerial work platforms.

72V LiFePO4 battery voltage meter

• Nominal voltage:76.8V
• Charging voltage: 87.6V
• Discharge cut-off voltage: 60V

It is suitable for 72V golf carts, electric cars, 6+ seater tour cars, and outboard motors.

LiFePO4 batteries are characterized by a state of charge (SOC). How does this relate to their voltage?

Battery state of charge (SOC) indicates a battery's charge level relative to its capacity. 0% of the SOC is depleted or discharged, and 100% is fully charged.

DOD is another measure of SOC, calculated as 100 - SOC (100% is fully charged, 0% is depleted). In general, SOC indicates a battery's current state when in use, whereas DOD indicates its useful life after repeated charge and discharge cycles.

The battery management system (BMS) intervenes when a battery reaches a low state of charge (approaching 0%). In the same way, when a battery approaches a high state of charge (approaching 100%), charging is slowed or stopped to protect it.

As an example, a 100Ah battery can discharge 30Ah. This results in a 30% SOC. The battery remains 30Ah after being charged to 100Ah and discharged to 70Ah.

For a lithium battery, the following chart shows the correlation between SOC and LiFePO4 voltage:

Charging Curve

Voltage: Battery voltage is generally regarded as a measure of how fully charged a battery is. When a LiFePO4 battery reaches 3.65V, it is fully charged.

Coulombmeter: Using this device, you can measure how much current flows into and out of the battery and calculate its charge and discharge rates in ampere-seconds (As).

Specific Gravity: SOC must be measured with a hydrometer. Density can be measured by buoyancy of a liquid.

LiFePO4 battery discharge curve

Discharge is the process of extracting electrical energy from a battery to power an electronic device. Discharge curves of batteries show the relationship between voltage and discharge time. In the figure below, the discharge curve of a 12V LiFePO4 battery is shown at various discharge rates.

LiFePO4 Battery Charging Parameters

Recommended charging parameters ensure battery performance, health, and durability. Each user must adhere to these parameters when charging. To ensure efficient energy storage and a longer battery life, make sure that the battery is not overcharged or undercharged. Listed below are the charging parameters for LiFePO4 batteries.

LiFePO4 battery constant voltage, floating charge and equalization voltage

Battery LiFePO4 has three voltage stages: bulk, float, and equalize. In the bulk stage, the battery is quickly charged to a certain voltage using a constant current. Float stage batteries receive a maintenance voltage. This prolongs the battery's life and efficiency. During the Equalize stage, the cells are balanced while an even charge is ensured.

How to Check LiFePO4 Battery Capacity

Regularly checking and monitoring your LiFePO4 battery will ensure long-term performance. The following methods can be used to measure LiFePO4 batteries accurately.

· Using a Multimeter-

Using a multimeter, you can measure battery capacity and voltage accurately.

· Battery Monitor-

With this reliable battery testing method, you can determine the battery's capacity. The battery monitor also predicts the battery's life in addition to evaluating its capacity, voltage, and discharge energy.

· Solar Charge Controller-

The capacity of LiFePO4 batteries is tested by solar charge controllers. This method can be beneficial to solar power systems.

· App Monitoring- 

It is possible to monitor and control LiFePO4 batteries remotely with some batteries. Performance, voltage, and other features can be monitored with smartphone apps.

Battery capacity can be calculated by multiplying discharge current (A) by discharge time (Hours).

Visualization of the structure and working principle of LiFePO4 battery

Structure

The positive electrode of the battery is LiFePO4, connected by aluminum foil to the battery's negative electrode. Lithium ions (Li+) pass through the polymer separator in the middle, while electrons (e-) are blocked. The negative electrode of the battery is connected to the negative electrode of carbon (graphite) on the right by copper.

How it LiFePO4 works

Charging Process:

Oxidation of LiFePO4 releases lithium ions (Li+) and electrons (e-).

Lithium ions (Li+) passing through the electrolyte and separator are received by a negative electrode.

Lithium ions (Li+) are stored in carbon (graphite) in an electrode's negative electrode.

Discharging Process:

The lithium ions (Li+) move from the negative electrode to the positive electrode through the electrolyte and separator.

At the positive electrode, lithium ions (Li+) and LiFePO4 undergo a reduction reaction, releasing electrons (e-).

Through an external circuit, electrons (e-) are released and power a power supply device.

During charging and discharging, lithium ions (Li+) and electrons (e-) cycle in the battery.

Factors Affecting the Cycle Life of LiFePO4 Batteries

· Charging and Discharging

The battery should not be overcharged or overdischarged. It is important to connect and disconnect the charger at the right time. Overcharging and overdischarging will reduce battery cycle life.

· Depth of Discharge

The service life of lithium iron phosphate batteries can be extended scientifically by avoiding deep discharges.

· Working Environment

LiFePO4 batteries should not be used in high or low temperatures to avoid affecting their performance. It is recommended to use a heated LiFePO4 battery if the battery will be used at a lower temperature.

Conclusion

The LiFePO4 voltage charts provide a comprehensive overview of the voltage characteristics, as well as the capacity and life expectancy of LiFePO4 batteries. This chart can be used to optimize the performance and life of LiFePO4 batteries.

Users can use these charts to determine the best voltage level, charge cycle, and life expectancy for LiFePO4 batteries, ensuring optimal performance and longevity.

FAQ

How to tell if my LiFePO4 battery is failing

Batteries don't last forever, of course. You should be able to use it for more than a decade. Your battery may be failing if you notice any of these signs.

· Charging takes unusually long

· Battery won’t charge

· Battery swelling

· When the battery is fully charged but the device shuts down.