If you're looking for a reliable and cost-effective way to store energy in your home or business, you may want to consider lead-acid batteries. Lead-acid batteries were the world's first rechargeable battery. They have been powering cars, motorcycles, boats, and other vehicles since 1859. They are also commonly used in backup power systems, solar systems, and other applications that require energy storage.
How Lead Acid Batteries Work
The lead-acid battery works through a chemical reaction that takes place between the lead plates and the sulfuric acid electrolyte. Before we understand how it works, we need to understand its structure.
A typical lead-acid battery consists of three main components:
- Lead Plates: These plates are made of lead (Pb) and are responsible for the battery’s ability to store and release electrical energy.
- Electrolyte: The electrolyte in a lead-acid battery is a mixture of sulfuric acid (H₂SO₄) and water. This electrolyte allows for the chemical reaction that generates electricity.
- Separator: The separator is a porous material that keeps the positive and negative plates from touching each other while allowing ions to pass through.
When the battery is discharging (giving power), the lead plates react with the acid, creating lead sulfate and releasing energy in the form of electrons, which flow out to power devices like your car or lights.
When you charge the battery, the process is reversed. The lead sulfate turns back into lead and lead dioxide, and the acid is restored, storing energy for later use.
So, the battery works like a rechargeable system: it stores energy when charging and gives it away when discharging, powering whatever you need.
Types of Lead Acid Batteries
The two main types are Flooded Lead Acid (FLA) and Valve-Regulated Lead Acid (VRLA), with VRLA being further divided into Absorbent Glass Mat (AGM) and Gel.
Flooded Lead Acid Batteries
The traditional ones are flooded lead acid batteries (FLA). They have fluid in them that you can see, and you need to check the level from time to time and add water if necessary. They are reliable and cheap, costing around $100 - $200, but you have to maintain them by checking the fluid level, and they can overflow if not handled properly.
Valve-Regulated Lead Acid (VRLA)
Valve-Regulated Lead Acid (VRLA) batteries don’t require maintenance because they’re sealed. You don’t need to worry about adding water. VRLA batteries come in two types:
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AGM (Absorbent Glass Mat) batteries: These are more compact and handle vibrations well. They charge faster and are good for situations where you need quick power. They’re a bit pricier, price is $150 - $300，but they last longer and are often used in cars and backup systems.
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Gel batteries: These use a gel inside to hold the liquid. They’re great for things like solar power systems because they’re very stable in hot or cold weather and handle deep discharges better. But, they are a bit expensive, costing $200 - $400. They need to be charged carefully.
Deep Cycle Lead Acid Batteries for Solar Systems
If you're on a budget, lead-acid batteries are a good choice for a solar system.
Flooded lead-acid batteries are the cheapest type and are suitable for off-grid solar systems that do not require frequent deep discharges, but they have a short life, are not very efficient, and are sensitive to extreme temperatures, especially cold weather .
AGM batteries are more convenient to maintain than flooded batteries, and their efficiency is about 90%. They are more expensive than flooded batteries, but much cheaper than lithium batteries, and are especially suitable for cold climates.
GEL batteries are ideal for systems that require deep discharge. They can withstand more discharges without significantly affecting life. Although they are more expensive than flooded and AGM batteries, they also last longer and have an efficiency of about 90%, is best suited for off-grid or grid-connected solar systems.
Are Lead-acid Batteries Better than Lithium Batteries For Solar Energy Storage?
The answer is no, lithium batteries are better than lead-acid batteries in the field of energy storage, and they are being used on a large scale in solar energy. Lithium batteries have the following advantages:
If you look at lifespan, lithium-ion batteries tend to last a lot longer—around 10 to 15 years—while lead-acid batteries last just 3 to 5 years. This means lithium-ion can handle 3,000 to 5,000 charge cycles, whereas lead-acid batteries only last for about 500 to 1,200 cycles before their performance drops off.
In terms of efficiency, lithium-ion batteries are much better—they can be 95% efficient, meaning less energy is lost when charging and discharging. On the other hand, lead-acid batteries are only about 80 to 85% efficient. Another big difference is energy density—lithium-ion batteries are far more compact and lighter because they store 150 to 250 Wh per kilogram, while lead-acid batteries store much less, about 30 to 50 Wh per kilogram.
Are Lead-acid Batteries Cheaper than Lithium-ion Batteries?
Yes, lead-acid batteries are cheaper than deep-cycle lithium-ion batteries. Lead-acid batteries are cheaper, taking a common 100 Ah, 12V battery as an example, the price of lead-acid batteries is only 1/3 to 1/2 of that of lithium-ion batteries. For example, the price of a lead-acid battery is about $100 to $300, while a lithium-ion battery of the same capacity will be between $600 and $1000.
Frequently Asked Questions about Lead Acid Batteries
How do I know when to charge my lead acid battery?
You can use a voltmeter or a hydrometer to measure the voltage or the specific gravity of your lead acid battery, respectively. These are indicators of the state of charge of your lead acid battery, which is the percentage of the available capacity of your lead acid battery. The higher the state of charge, the higher the voltage or the specific gravity. The lower the state of charge, the lower the voltage or the specific gravity. You can use the following table to compare the state of charge, the voltage, and the specific gravity of your lead acid battery:
| State of charge (%) | Voltage (V) | Specific gravity |
|---|---|---|
| 100 | 12.7 | 1.265 |
| 75 | 12.4 | 1.225 |
| 50 | 12.2 | 1.190 |
| 25 | 12.0 | 1.155 |
| 0 | 11.9 | 1.120 |
As a general rule of thumb, you should charge your lead acid battery when the state of charge drops below 50%, or the voltage drops below 12.2 V, or the specific gravity drops below 1.190. You should also avoid discharging your lead acid battery below 20%, or the voltage below 11.9 V, or the specific gravity below 1.120, as this can damage your lead acid battery and reduce its lifespan.
How do I charge my lead acid battery?
You can use a charger that is designed for lead acid batteries and that matches the voltage and current specifications of your lead acid battery. You should also use a smart charger that can adjust the charging voltage and current according to the state of charge and the temperature of your lead acid battery. A smart charger can optimize the charging efficiency and prolong the battery life by using a three-stage charging algorithm, which consists of bulk, absorption, and float stages.
- Bulk stage: The charger delivers a constant and high current to the lead acid battery until the voltage reaches a predetermined level, usually 14.4 V. This stage restores about 80% of the capacity of the lead acid battery.
- Absorption stage: The charger reduces the current and maintains the voltage at a constant level, usually 14.4 V, until the current drops to a predetermined level, usually 0.1 A. This stage restores the remaining 20% of the capacity of the lead acid battery and equalizes the charge of the individual cells.
- Float stage: The charger reduces the voltage and maintains a low and constant current, usually 13.6 V and 0.05 A, to the lead acid battery. This stage maintains the full charge of the lead acid battery and compensates for the self-discharge.
How do I store my lead acid battery?
Store the lead-acid battery in a cool, dry place away from direct sunlight, rain, dust and fire. Disconnect the lead-acid battery from the charger and load, and unplug the cables and connectors from the terminals.
Conclusion
Lead-acid batteries are one of the oldest and most widely used types of rechargeable batteries in the world. They have many advantages, such as low cost, high capacity, long cycle life and wide compatibility. They are also easy to install, operate and maintain, and are safe and reliable. Although it is not particularly suitable for solar systems compared to lithium batteries, if your budget is not sufficient, lead-acid batteries can also provide a reliable and cost-effective energy storage solution for your home or business.
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