LiFePO4 vs Lead Acid battery for solar – 2023 report

LiFePO4 and lead acid batteries are two common types of rechargeable batteries used in various applications. LiFePO4 batteries are widely used in electric vehicles and renewable energy storage systems due to their deeper depth of discharge, longer cycle life, faster charging time, and higher charging efficiency compared to lead acid batteries.

Lead acid batteries are commonly used in automobiles and other applications that require a high power-to-weight ratio. While they may have a shorter cycle life and lower efficiency, they can be a better option when cost is a major consideration.

This article explores the working principles of these batteries and compares their pros and cons.

 

What is LiFePO4 battery and how does it work?

A LiFePO4 battery, also known as a lithium iron phosphate battery, is a type of rechargeable battery that is commonly used in electric vehicles and renewable energy storage systems. It is composed of four main components: a cathode (positive electrode), an anode (negative electrode), a separator, and an electrolyte.

The LiFePO4 battery works by using lithium ions to move back and forth between the anode and cathode electrodes.

During charging, lithium ions move from the cathode to the anode, where they are stored in the crystal structure of the LiFePO4 material.

When the battery is discharged, the process is reversed, with the lithium ions moving from the anode to the cathode and creating an electrical current.

 

What is Lead Acid battery and how does it work?

A lead-acid battery is a type of rechargeable battery commonly used in automobiles, uninterruptible power supplies (UPS), and other applications requiring a high power-to-weight ratio. It consists of a number of lead and lead oxide plates immersed in an electrolyte solution of sulfuric acid.

When the battery is discharged, the sulfuric acid reacts with the lead and lead oxide plates, forming lead sulfate and water. This chemical reaction releases electrons, which flow through the circuit and power the device.

When the battery is charged, the process is reversed, with lead sulfate and water turning back into lead and lead oxide plates and sulfuric acid.

 

LiFePO4 vs Lead Acid battery: Pros and Cons

 

Depth of Discharge

One key difference between LiFePO4 and lead acid batteries is their depth of discharge, which refers to the amount of a battery's capacity that has been used up during a discharge cycle. In other words, it is the percentage of the battery's total capacity that has been depleted.

LiFePO4 batteries typically have a deeper depth of discharge compared to lead acid batteries. This means that LiFePO4 batteries can be discharged to a lower state of charge without damaging the battery or significantly reducing its lifespan.

In general, LiFePO4 batteries can be discharged to 80-90% of their total capacity. This makes them well-suited for applications where longer battery life and deeper cycling are important, such as in electric vehicles, solar power systems, and backup power systems.

In contrast, lead acid batteries should not be discharged below 50% of their total capacity in order to avoid damaging the battery or reducing its lifespan.

Some specialized types of lead acid batteries, such as deep cycle batteries, can be discharged to slightly deeper levels, but they still generally have a shallower depth of discharge compared to LiFePO4 batteries.

 

Cycle life

LiFePO4 and lead-acid batteries have different characteristics when it comes to their cycle life, which refers to the number of charge and discharge cycles a battery can go through before it begins to degrade.

LiFePO4 batteries typically have a longer cycle life than lead-acid batteries. This is because LiFePO4 batteries are better at withstanding repeated charge and discharge cycles without experiencing significant degradation.

Lead-acid batteries can suffer from a shorter cycle life if they are subjected to deep discharges or are not properly maintained. This is because lead-acid batteries are more sensitive to the depth of discharge than LiFePO4 batteries. They can have a longer cycle life if they are not frequently discharged below 50% of their capacity.

Overall, while both LiFePO4 and lead-acid batteries can provide reliable energy storage, LiFePO4 batteries generally offer a longer cycle life and are better suited to applications where frequent cycling is required. Lead-acid batteries may be a better option in situations where the battery will be used less frequently or where cost is a major consideration.

 

Charge Rate

LiFePO4 batteries can be charged at a faster rate than lead acid batteries. LiFePO4 batteries can handle a charge rate of up to 1C, meaning they can be charged at a current equivalent to their capacity in ampere-hours (Ah).

For example, a 100Ah LiFePO4 battery can handle a charge rate of up to 100A. In contrast, lead acid batteries typically have a recommended charge rate of between 0.2C to 0.25C, which means that a 100Ah lead acid battery should be charged at a maximum current of 20-25A.

 

Charging time

Due to their higher charge rate, LiFePO4 batteries can be charged much faster than lead acid batteries. A LiFePO4 battery can be charged to 80% capacity in 1-2 hours, while a lead acid battery typically takes 8-10 hours to reach 80% capacity.

 

Efficiency

LiFePO4 batteries have a higher charging efficiency than lead acid batteries, meaning that more of the energy from the charging source is stored in the battery rather than being lost as heat. This results in faster charging times and less energy waste.

 

Capacity

LiFePO4 batteries typically have a higher capacity than lead-acid batteries of the same size, meaning they can store more energy. This is because LiFePO4 batteries have a higher energy density, which allows them to store more energy in a smaller space.

Additionally, LiFePO4 batteries have a higher usable capacity compared to lead-acid batteries. This means that they can discharge more of their total capacity before they need to be recharged. Lead-acid batteries, on the other hand, have a lower usable capacity and should not be discharged beyond a certain point, as doing so can damage the battery.

 

Safety

One of the advantages of LiFePO4 batteries is their stability and safety. They are less prone to overheating and thermal runaway than other types of lithium-ion batteries, and they are less likely to catch fire or explode.

Lead-acid batteries generate hydrogen gas during charging, which can be explosive in certain conditions. LiFePO4 batteries, on the other hand, do not generate gas during charging and are therefore safer in this regard.

Lead-acid batteries are more prone to leakage than LiFePO4 batteries. This can be a safety hazard in situations where the leaked electrolyte comes into contact with skin or eyes.

Lead-acid batteries contain lead and other heavy metals, which can be toxic if they leak or are disposed of improperly. LiFePO4 batteries, on the other hand, do not contain any heavy metals and are therefore safer for the environment and for human health.

Overall, LiFePO4 batteries generally have a better safety profile due to their lower risk of thermal runaway, gas generation, leakage, and toxic heavy metal content.

 

Energy Density

LiFePO4 batteries have energy density, which means they can store a lot of energy in a relatively small and lightweight package. They are also highly durable and can withstand a large number of charge and discharge cycles, making them a popular choice for applications that require long-lasting and reliable energy storage.

However, lead-acid batteries are heavy and have a relatively low energy density, which means they have a limited amount of energy stored per unit of weight. Additionally, they require maintenance, such as periodic refilling of the electrolyte solution and cleaning of the terminals.

 

Round-trip efficiency

The round-trip efficiency of a battery refers to the amount of energy that can be retrieved from a battery relative to the amount of energy that was put into it.

LiFePO4 batteries typically have a round-trip efficiency of around 92-96%, meaning that almost all of the energy put into the battery can be retrieved. In contrast, lead-acid batteries typically have a round-trip efficiency of around 75-85%, meaning that some energy is lost during charging and discharging.

 

Maintanance

LiFePO4 and lead acid batteries have significant differences when it comes to maintenance.

 

Maintenance of LiFePO4 batteries:

• LiFePO4 batteries require very little maintenance compared to lead acid batteries.

 

• They do not require regular equalization or water refilling like lead acid batteries.

 

• They also have a longer lifespan and can typically last up to 10 years or more, reducing the need for frequent replacement and maintenance.

 

Maintenance of lead acid batteries:

• Lead acid batteries require regular maintenance to ensure they operate at peak performance.

 

• They require regular water refilling, especially in hot climates or during heavy use, to prevent the plates from drying out and sulfation from forming.

 

• They also require regular equalization to balance the voltage of each cell and prevent overcharging or undercharging.

 

• Failure to maintain a lead acid battery can significantly reduce its lifespan, and they typically need to be replaced every 3 to 5 years.

 

In short, LiFePO4 batteries, on the other hand, require less maintenance and are less prone to damage from overcharging.

 

LiFePO4 vs Lead Acid battery: Which is best for solar?

When it comes to solar energy storage, Lithium Iron Phosphate (LiFePO4) batteries are generally considered superior to lead-acid batteries.

LiFePO4 batteries have a number of advantages over lead-acid batteries, including higher energy density, longer cycle life, faster charging time, and lower self-discharge rate. LiFePO4 batteries are also generally more durable, with less risk of damage from deep discharging or overcharging. In addition, LiFePO4 batteries do not produce toxic gases or require maintenance like lead-acid batteries do.

While lead-acid batteries may be less expensive upfront, their lower lifespan and higher maintenance needs can ultimately make them more costly in the long run. Furthermore, lead-acid batteries tend to lose capacity in extreme temperatures, whereas LiFePO4 batteries can operate effectively in a wide range of temperatures.

In summary, while lead-acid batteries may be cheaper upfront, the long-term benefits of LiFePO4 batteries make them the better option for solar energy storage. LiFePO4 batteries offer higher energy density, longer cycle life, faster charging time, lower self-discharge rate, greater durability, and lower maintenance requirements.