As energy demands continue to climb and the world continues its quest for more sustainable options, the need for alternative energy sources such as solar energy has also increased. These days, more households and businesses are adopting solar energy setups to satisfy their energy needs.
Most people tend to focus more on solar panels when setting up solar systems. However, the batteries are the powerhouse of the solar setup, as they store electric charges and dispense them when necessary.
Although the sun’s energy is limitless and free for us to use, it is not always available. And in this day and age, we often require 24/7 electricity. Imagine enjoying uninterrupted electricity all day, but at night, when you need it most, it’s unavailable.
Now, that is not a pleasant experience. Still, it’s what we’d have to constantly deal with without solar batteries in a solar installation setup.
Besides compensating for when the sun is unavailable, solar batteries also determine the efficiency and performance of a solar setup. Just as each home has unique energy needs, different batteries are designed to fit these unique needs.
In this article, we’ll discuss the various types of solar batteries, their advantages and disadvantages, and their best uses.
Types of Solar Batteries
There are about four major solar batteries readily available in the market. Each of these batteries has characteristics that make it different from the others and specific use cases based on energy requirements and needs. These batteries include:
1. Lead-Acid Batteries
Lead-acid batteries, also known as deep cycle batteries, have been a part of solar power setups for years due to their affordability. These batteries are known for constantly supplying steady power for prolonged periods. Lead batteries are best used in hybrid or off-grid solar system setups. Common types of lead acid batteries include:
Gel batteries: Gel batteries are sealed lead-acid batteries using gel-like electrolytes. These batteries can perform deep discharges, which makes them ideal for solar energy systems. They perform well in colder regions and are not commonly used in Nigeria.
Flat plate batteries: These lead-acid batteries are ideal for small solar setups with minimal energy requirements. However, they have a shallow discharge capacity, making them unfit for home use.
Tubular batteries: These are commonly used in solar setups due to the tubular design of their positive plates, specifically designed for use with inverters. The positive plate of tubular batteries comprises high-pressure gauntlets that prevent corrosion and ensure a stronger battery life.
Tubular batteries are perfect for hybrid and off-grid systems. They provide a stable power backup system that can handle long power cuts, operate at high temperatures, and integrate well with renewable energy sources. Tubular batteries are also resistant to overcharging, have a low self-discharge rate, and can operate in a wide range of temperatures.
Generally, lead-acid batteries have been tested and trusted for solar system applications over the years. More specifically, tubular batteries have proven to be the best kind of lead-acid batteries, which is why Ecopulse makes use of tubular batteries for applications that require a lead-acid battery.
2. Lithium Batteries
Although they are generally more expensive, lithium batteries are more efficient than lead-acid batteries. This is because of their superior electrochemical properties and higher depth of discharge. Additionally, they can accept higher charge currents without overheating, making them fast-charging.
- Lithium-ion batteries: These batteries have a higher discharge capacity (DoD) than lead acid batteries and a longer lifespan. Lithium-ion batteries also have a more compact build and are lightweight compared to their lead-acid counterparts. They have high energy density, which allows them to store higher amounts of energy within a smaller space.
Lithium-ion batteries also have no “memory effect”, a situation in which continuous charging and discharging causes the battery to develop a lower capacity over time.
- Lithium iron phosphate batteries: In addition to the general advantages they offer, lithium iron phosphate batteries are the best lithium batteries for solar applications due to their stability, safety, and long life span. They can also perform optimally at high temperatures.
3. Nickel-Cadmium Batteries
Although nickel-cadmium batteries require little maintenance, are durable, and do not require complex management systems, they are rarely used in home solar installations due to health and safety concerns. Instead, they are used for large-scale energy storage applications.
4. Flow Batteries
Flow batteries use liquid electrolytes, which are usually non-flammable. This makes them safer than lithium-ion batteries and able to dispense consistent power over extended periods (ranging from hours to days).
In most batteries, a full discharge of the battery’s energy shortens the battery’s lifespan over time. However, with flow batteries, their lifespan is not harmed even when they are frequently deeply discharged.
Essentially, flow batteries are currently the best solar batteries. However, since they are still a new technology, they are much more expensive than lithium batteries. Lithium batteries are more commonly used because they are cheaper and smaller.
Factors to Consider Before Choosing a Solar Battery
Depending on your energy needs and what you hope to get from your solar system, here are key factors to consider before you say ‘yes’ to that battery.
- Depth of Discharge (DoD): The depth of discharge refers to the amount of a battery’s capacity that has been discharged relative to its maximum capacity. For instance, if a battery’s depth of discharge is 50%, half of the battery’s capacity has been used up.
Batteries with higher minimum DoDs are often more beneficial to clients, as they indicate that most of the battery’s capacity is used before recharging. This ensures that the user gets the most out of the battery without adversely affecting the battery life. Lithium batteries often have higher DoDs (90-100%) and are more popular.
The minimum depth of discharge is the minimum level to which the battery can be discharged without adversely affecting its health.
Cost: This is another important factor to consider while selecting batteries. For instance, lithium batteries are more costly initially but offer more benefits to the user over time. Lead-acid batteries, on the other hand, are a bit cheaper and still do the job. However, they do not offer as many advantages as lithium batteries over time.
Round-trip efficiency: This refers to the ratio of energy input to output for a battery. Simply put, the round-trip efficiency is the ratio of the energy you can get from your battery to the amount of energy it took to charge it. For instance, if it took 10kW to charge the battery fully, and you can only use 9kW, it means the battery has a round-trip efficiency of 90%.
Batteries with higher round-trip efficiencies are more efficient because they waste less energy during the charging and discharging process. Lithium batteries have much higher round-trip efficiencies than their lead-acid counterparts.
- Battery life: Solar batteries cycle daily. A cycle refers to the amount of times a battery charges and gets drained. Batteries with higher cycles tend to last for longer periods. Different solar batteries have specified cycles or the number of years of usage. You should consider the battery life when deciding how long to use your solar system.
For instance, if a battery is warrantied for 5,000 cycles or 10-15 years at 60% DoD, it means that if the battery is used at a 60% DoD, after 5,000 cycles, the battery would have lost a significant portion of its capacity.
Maintenance requirements: Batteries with the least maintenance requirements are more beneficial for optimal solar setup utilization.
Capacity refers to the amount of energy a solar battery can hold. For example, Lithium-ion and lithium-iron phosphate batteries have higher capacities than their lead-acid counterparts.
Energy density: A battery’s energy density refers to how much energy is stored per unit mass. Lithium-ion batteries often have much higher energy densities than other batteries.
For instance if a lithium-ion and lithium iron phosphate battery weigh 5kg, the lithium-ion battery will store more energy than its LiFePO counterpart. Li-ion is perfect if you just want to store more energy. However, LiFePO is more tolerant to frequent charging and discharging over time.
The table below compares the important factors of various batteries:
| Factors | Lead-acid batteries | Lithium-ion batteries | Lithium iron phosphate batteries | Nickel-Cadmium batteries | Flow batteries |
|---|---|---|---|---|---|
| Maintenance requirements | Requires maintenance 2 - 3 times yearly | No maintenance | Little to no maintenance | Requires regular maintenance | Requires moderate maintenance |
| Depth of Discharge | 50 - 80% | 80 - 95% | Up to 100% | 80% | Up to 100% |
| Round trip efficiency | 70 - 80% | 85 - 95% | 90 - 95% | 70 - 80% | 75 - 80% |
| Lifespan (Cycles) | 300 - 700 | 500 - 1,000 | 1,000 - 5,000 | 500 - 1,000 | 10,000 - 20,000 |
| Energy density | 30 - 50 Wh/kg | 150 - 300 Wh/kg | 90 -120 Wh/kg | 45 - 80 Wh/kg | 100 |
In addition to these factors, consult trusted solar professionals, such as those at Ecopulse, to determine the perfect battery for your solar needs.
Impact of Battery Choice on Solar System Setup and Performance
Since the battery is regarded as the powerhouse of home solar systems, the choice of battery used in the installation process affects the system’s overall performance. These effects can be seen in:
Capacity of solar setup: Batteries with higher capacities indicate that more energy can be stored, and the solar system can provide power for longer hours, especially during peak usage. The capacity advantage is especially prominent in lead-acid batteries.
Installation and Maintenance: Battery quality also affects the maintenance level required for your solar system. Although lithium-ion batteries cost more initially than their lead-acid counterparts, they generally require less maintenance.
Durability and System Lifespan: Batteries with a longer lifespan have less frequent downtime, reducing maintenance costs. Lead-acid batteries usually have a lifespan of 3-5 years, unlike their lithium counterparts, which have life spans between 10-15 years.
Scalability: The current choice of batteries determines the ease of expanding the solar system as energy needs increase in the future.
Conclusion
The choice of solar batteries affects solar systems’ performance in more ways than one. To get a full picture of the best battery suitable for special applications, professionals must assess some of the factors listed above on a deeper level. Additionally, specific energy requirements would require some extra factors to be considered. Thus, you may need expert opinions from trusted solar energy companies like Ecopulse.