Which is Better: Lead Acid or Lithium Ion Battery? A Comprehensive Comparison

In recent years, the debate between lead acid and lithium ion batteries has gained significant attention, especially for energy storage systems and renewable energy applications. As technology advances, consumers and industries alike are faced with the challenge of choosing between these two popular battery types. In this article, we’ll explore the key differences between lead acid and lithium ion batteries, focusing on performance, efficiency, lifespan, and compatibility, so you can make an informed decision on which is better: lead acid or lithium ion battery for your specific needs.

Understanding the Basics: Lead Acid vs Lithium Ion

Before diving into the comparison, let's first take a look at the basic characteristics of both battery types.

Lead Acid Battery: Developed in the 19th century, lead acid batteries have been the standard for many applications, including automotive, off-grid energy storage, and backup power systems. They are known for their relatively low initial cost and established technology.

Lithium Ion Battery: Lithium ion batteries, particularly lithium iron phosphate (LiFePO4) types, have gained immense popularity in recent years due to their superior energy density, longer lifespan, and higher efficiency compared to traditional lead acid batteries. These batteries are commonly used in electric vehicles, renewable energy storage, and consumer electronics.

Key Differences Between Lead Acid and Lithium Ion Batteries

1. Energy Density and Weight

One of the most significant differences between lithium iron phosphate and lead acid batteries is energy density. Lithium ion batteries are much lighter and more compact, offering a higher energy density, which means they can store more energy in a smaller space. This is particularly important in applications where weight and space are limited, such as electric vehicles and portable energy storage systems.

In contrast, lead acid batteries are bulky and heavy, making them less suitable for mobile applications. Their lower energy density means they take up more space and weight to provide the same energy output as a lithium ion battery.

2. Lifespan and Durability

When it comes to lifespan, lithium ion batteries typically outlast lead acid batteries by a significant margin. A typical lithium ion battery can endure between 7000 and 9000 charge cycles, depending on the quality and usage conditions. In contrast, lead acid batteries usually last around 1000 to 1500 charge cycles before their performance starts to degrade.

This significant difference in lifespan can lead to long-term cost savings with lithium ion batteries, despite their higher initial cost.

3. Efficiency and Performance

Lithium ion batteries are more efficient than lead acid batteries, particularly in terms of energy usage. Lithium ion batteries can be discharged to a much lower percentage of their capacity (up to 80%-90%) without damaging the battery, whereas lead acid batteries should only be discharged to around 50% to avoid damage and reduce their lifespan.

Additionally, lithium ion batteries have faster charging times and higher overall efficiency, meaning less energy is wasted during the charging process. In comparison, lead acid batteries are slower to charge and less efficient, especially as they age.

4. Maintenance and Cost

While lead acid batteries are generally cheaper upfront, they require regular maintenance, such as checking electrolyte levels and ensuring the battery is charged properly to avoid damage. Lithium ion batteries, on the other hand, require minimal maintenance and typically come with a Battery Management System (BMS) that helps protect the battery from overcharging, over-discharging, and overheating.

Although lithium ion batteries have a higher initial cost, their long lifespan, efficiency, and low maintenance requirements can make them more cost-effective in the long run.

5. Safety and Risk of Damage

Lithium ion batteries are generally considered safe when used correctly, but they are more sensitive to extreme conditions like overcharging, extreme temperatures, and physical damage. Overcharging or physical damage to a lithium battery can lead to risks such as thermal runaway, fire, or explosion.

Lead acid batteries, while generally safer in terms of risk of fire, can also pose risks, particularly due to their corrosive acid. However, they are generally less sensitive to environmental conditions and physical impacts compared to lithium batteries.

Can lead-acid batteries and lithium batteries be charged with each other?

Lead-acid batteries and lithium batteries have different charging requirements and characteristics during the charging process, so they cannot be charged directly with each other. Here are some of the main differences when charging the two, and why they cannot be charged directly with each other:

1. Different voltages

Lead-acid batteries: Generally speaking, lead-acid batteries have a lower operating voltage range. The charging voltage of 12V lead-acid batteries is usually around 13.8V - 14.4V (for ordinary 12V lead-acid batteries). For deep-cycle lead-acid batteries, the charging voltage will be slightly higher.

Lithium batteries: The charging voltage of lithium batteries is higher, usually between 3.6V - 4.2V (single cell), and most lithium batteries use 3.2V (LiFePO4) or 3.7V (NCM) as the single cell voltage, and different charging voltages are required depending on the battery type. A typical 12V lithium battery system When charging, the charging voltage is generally around 14.4V - 14.6V.

2. The charging current is different from the charging curve

Lead-acid battery charging curve: The charging process of lead-acid batteries is usually divided into three stages: constant current, constant voltage and floating charge. The charging current is fixed in the constant current stage, and when it is charged to a certain voltage, it enters the constant voltage stage, and finally enters the floating charge stage to keep the battery voltage stable.

Lithium battery charging curve: Lithium batteries usually use the constant current-constant voltage charging method, but their charging process is different from that of lead-acid batteries, especially lithium batteries have stricter protection against overcharging and over-discharging. During the charging process, there will be a built-in battery management system (BMS) to ensure the safety of the battery.

3. Different charger designs

Lead-acid battery charger: The charger design of lead-acid batteries is usually based on the characteristics of their charging curve. The charging current and voltage are preset and suitable for the chemical characteristics of lead-acid batteries.

Lithium battery charger: Lithium batteries require chargers designed specifically for lithium batteries because they have more precise requirements for charging voltage and current. If an unsuitable charger is used, it may cause overcharging, overheating, and even danger.

4. Battery Management System (BMS)

Lead-acid batteries: usually do not have a built-in battery management system (BMS), and most of the management and protection functions rely on external chargers and protection circuits.

Lithium batteries: Lithium batteries usually have a built-in battery management system (BMS), which can control the charging process, prevent overcharging, over-discharging, overheating, etc., and ensure battery safety.

5. Why can't they be charged directly?

Voltage difference: Lead-acid batteries and lithium batteries have different charging voltage ranges. If a lithium battery is charged directly with a lead-acid battery charger, it may cause the lithium battery to be overcharged or damaged; vice versa, charging a lead-acid battery with a lithium battery charger may not be fully charged.

Charging curve mismatch: Different charger designs will lead to incompatible charging processes, and the charging current and voltage may cause battery damage or incomplete charging.

Safety issues: Especially for lithium batteries, because they are very sensitive to charging voltage and current, inappropriate chargers and charging methods may cause battery overheating, fire, or even explosion.

6. Indirect charging (through a suitable converter)

Although direct mutual charging is not feasible, in some cases, charging between different types of batteries can be achieved through adapters or converters. For example:

DC-DC converters: These can convert the voltage of a lithium or lead-acid battery to the required charging voltage of another battery type. For example, converting the voltage of a 12V lithium battery to a voltage suitable for charging a lead-acid battery.

Bidirectional converters: There are systems that can achieve energy conversion between batteries, allowing energy transfer between different batteries, but these require specialized control circuits and management systems.

Can Lithium Battery Be Connected to Lead Acid Battery?

A common question that arises is, can lithium battery be connected to lead acid battery? The answer is no, it is generally not recommended to directly connect lithium ion batteries to lead acid batteries in the same system.

Due to the differences in voltage, charging profiles, and internal resistance, lead acid and lithium ion batteries should not be directly connected or used in parallel. Connecting them could cause one battery type to overcharge or over-discharge, leading to potential damage, reduced lifespan, and safety risks.

If you need to combine both types of batteries in a system, it is crucial to use appropriate battery management systems (BMS), DC-DC converters, or charge controllers designed to regulate the charging and discharging processes of each battery type independently.

If you encounter any issues while choosing a storage system or if you're interested in learning more about lead acid batteries and lithium ion batteries, feel free to reach out to SUNESS.