Solar Batteries for South Africa

 

Types of Solar batteries

There are several types of batteries that can be used in solar power systems, each with their own advantages and disadvantages. Some of the most common types of batteries used in solar systems include:

1. Lead-acid batteries: These are the most widely used type of battery for solar systems, as they are relatively inexpensive and have been used in a variety of applications for many years. There are two types of lead-acid batteries: flooded batteries (which require periodic maintenance) and sealed batteries (which are maintenance-free).

2. Lithium-ion batteries: These batteries have become increasingly popular in recent years, as they offer a higher energy density and longer lifespan than lead-acid batteries. They are also lighter and more compact, making them easier to install and transport.

3. Nickel-cadmium batteries: These batteries were commonly used in solar systems in the past, but have largely been replaced by other battery technologies due to their high toxicity and environmental concerns.

4. Flow batteries: These batteries use two tanks of electrolyte solution to store energy, which allows for larger storage capacities and longer lifespans than other battery types. They are still relatively expensive and less commonly used in solar systems, but may become more popular as technology improves.

In South Africa the choice of battery for a solar system will depend on a variety of factors, including the system's energy requirements, available space, budget, and performance needs. Only Lead acid and Lithium ion batteries are feasible at the moment.

 

Which type of solar battery is best?

Lead acid battery advantages:

1. Cost: Lead-acid batteries are typically less expensive than lithium ion.

2. Availability: Because lead-acid batteries have been used in a variety of applications for many years, they are widely available and easy to find.

3. Safety: Lead-acid batteries are relatively safe to use and handle, as they do not contain highly toxic materials and are not as prone to thermal runaway.

4. Maintenance: While flooded lead-acid batteries do require some maintenance (such as topping off the electrolyte solution), they are generally easy to maintain and service.

5. Recyclable: Lead acid batteries are mostly recyclable, the lead is 100% recycled and the ABS casing can also be recycled.

 

Lead acid battery disadvantages:

1. Shorter lifespan: Lead-acid batteries have a shorter lifespan than some other types of batteries, typically lasting between 3-5 years. See the section below on how to design to maximise the lifespan of a lead acid battery.

2. Limited depth of discharge: Lead-acid batteries should not be discharged below a certain level, as this can damage the battery and shorten its lifespan. Check on the battery spec sheet, the rule of thumb is that a lead acid battery should not be discharged more than 70% of its total charge. This means that 10kWh of lead acid battery does NOT equal 10kWh of lithium ion batteries, because you can only sustainably discharge 30% of a lead acid battery, so 10kWh of a lead acid battery means that you have 3kWh of USABLE energy. You could use the full 10kWh but then your battery life will be severely impaired. A lithium battery can be 100% discharged.

3. Heavy and bulky: Lead-acid batteries are relatively heavy and bulky, which can make them difficult to transport and install. Stands for lead acid batteries are hard to find. It may be difficult to install lead acid batteries above the ceiling and below the roof because they weigh so much.

4. Lower energy density: Lead-acid batteries have a lower energy density than lithium ion batteries, which means that they may not be able to store as much energy in the same amount of space. In SA this is not normally a problem unless you live in an appartment.

5. Worth Stealing: lead acid batteries are often stolen in SA, especially from cellphone towers. Lead acid batteries can be sold at any scrap yard, while lithium ion batteries are harder to sell (although worth more per kg).

 

Lithium ion battery advantages in a solar system

1. High energy density: Lithium-ion batteries have a higher energy density compared to lead-acid batteries, which means they can store more energy in a smaller space. This is not a huge factor in South Africa but if you live in an appartment it may be.

2. Longer lifespan: Lithium-ion batteries typically have a longer lifespan than lead-acid batteries. While the lifespan of a lead-acid battery is typically around 5 years, the lifespan of a lithium-ion battery can be up to 15 years or more, depending on the specific chemistry and usage.

3. Higher efficiency: Lithium-ion batteries are more efficient at storing and releasing energy than lead-acid batteries. This means that less energy is lost during the charging and discharging process, resulting in higher overall efficiency of the solar system.

4. Faster charging: Lithium-ion batteries can be charged faster than lead-acid batteries, which can be beneficial for solar systems that rely on intermittent sources of energy such as solar panels.

5. Lower maintenance: Lithium-ion batteries require less maintenance compared to lead-acid batteries. Lead-acid batteries require regular maintenance such as checking the water levels and cleaning the terminals, while lithium-ion batteries do not require any regular maintenance.

6. Smaller size: Lithium-ion batteries are smaller and lighter compared to lead-acid batteries, which makes them easier to install and transport.

7. Scalability: Lithium-ion batteries can be scaled up or down depending on the energy storage requirements of the solar system, making them more flexible and adaptable than lead-acid batteries.

 

Lithium ion battery disadvantages

1. Cost: Lithium-ion batteries are generally more expensive than lead-acid batteries.

2. Safety concerns: While lithium-ion batteries are generally safe, they can be more volatile than lead-acid batteries.. If the battery is damaged or overheats, it can catch fire or explode. This is why it is important to choose a high-quality lithium-ion battery with built-in safety features.

3. Limited lifespan: Lithium-ion batteries have a limited lifespan, typically around 5-10 years. After this time, they may need to be replaced, which can be costly.

4. Limited capacity: Lithium-ion batteries have a limited capacity, so you may need to install multiple batteries to meet your energy needs. This can also be expensive.

5. Battery Management: usually Lithium-ion batteries require a BMS (Battery Management System), which is often built into systems. If it is not, then it can be an additional cost.

Where can I buy batteries for solar applications?

You can buy batteries directly from the wholesalers but beware that there are dangers! If you are just replacing an old battery, then you have little to worry about. If you are creating a solar system, then it might be safer to get a solar installer to design the system for you.

1. Mantech Electronics - This is an electronics store that sells a variety of batteries, including lithium-ion batteries, at competitive prices. www.mantech.co.za

2. Voltex - This is a distributor of electrical and lighting products that sells lead acid and lithium-ion batteries at reasonable prices.

3. Sustainable.co.za - This is an online store that specializes in eco-friendly and sustainable products, including lithium-ion batteries for solar energy storage.

4. Battery Centre - This is a retail chain of battery stores that sells a variety of batteries, best known for car batteries but also including lithium-ion batteries.

5. Takealot.com - This is an online retailer that sells a variety of products, including lithium-ion batteries from various brands, at competitive prices. Beware that the warranty may be different for different sellers.

6. Stolen batteries- this is obviously the cheapest but we do not recommend this.

7. Second hand batteries - not recommended unless you have the equipment to ascertain the condition of the battery. Second hand batteries may be an option for high theft risk areas, where it is likely that the battery will be stolen in a few months anyway.

8. Solar installers sell batteries, check for one in your area.

 

 

How to design a system to have low life cycle battery costs?

The rule of thumb is get 50% more battery capacity than you think that you need. If you want to be completely off grid, then get 100% more battery capacity than you think that tyou will need.

1. Proper sizing: Sizing the battery bank properly is critical to ensure that the batteries are not overworked or underutilized. Overworking batteries will shorten their lifespan, while underutilizing batteries will result in a higher cost per kWh of energy stored.

2. Choosing the right battery type: Different battery chemistries have different lifespans and costs, so choosing the right type of battery is critical. For example, lithium-ion batteries typically have a longer lifespan than lead-acid batteries and can be more cost-effective over the long term.

3. Optimize charging: Overcharging or undercharging batteries can reduce their lifespan and increase maintenance costs. By optimizing the charging profile, you can reduce battery degradation and extend the lifespan of the battery.

4. Proper maintenance: Proper maintenance of the battery bank is critical to ensure that the batteries last as long as possible. Regular inspections, cleaning, and testing can help identify issues before they become major problems.

5. Using energy-efficient equipment: Energy-efficient equipment such as inverters, charge controllers, and appliances can help reduce the energy consumption of the system, which can help reduce the size and cost of the battery bank.

6. Minimizing deep discharges: Deep discharging batteries can significantly reduce their lifespan, so minimizing deep discharges is important. By sizing the battery bank correctly and optimizing charging, you can reduce the frequency of deep discharges.

Graph of life cycles for a lead acid battery vs depth of discharge

From the above graph you can see that if you completely discharge a lead acid battery (and this is for a deep cycle battery), then you can expect 300 cycles, this is about a year of use. If you install 3 times the batteries that you need and only discharge to 30% of the total capacity of the batteries, then you can expect 1500 cycles, or 5 times the life. Pay 3 times more but get 5 times more.

 

Lithium batteries are known to be dangerous, are they dangerous for solar applications?

Lithium-ion batteries have been known to pose some safety risks (especially Samsung Galaxy Note7 on airplanes), they can be used safely in solar applications with proper installation, operation, and maintenance procedures in place.

Here are some of the safety risks associated with lithium-ion batteries and how they can be mitigated in solar applications:

1. Overcharging: Overcharging lithium-ion batteries can cause them to overheat and possibly catch fire or explode. To prevent overcharging, solar systems must be equipped with charge controllers that are designed to protect the batteries from overcharging.

2. Short circuits: Short circuits can occur if the positive and negative terminals of the battery are connected, causing the battery to overheat and possibly catch fire or explode. To prevent short circuits, solar systems must be designed with proper wiring and connections that are secure and free from damage.

3. Thermal runaway: Thermal runaway occurs when the battery overheats and begins to self-heat, which can cause a chain reaction that leads to an explosion or fire. To prevent thermal runaway, solar systems must be designed with proper cooling and ventilation systems that allow heat to dissipate from the battery bank. This can be a problem in South Africa if you install your batteries above your ceiling as it gets really warm and can prevent your batteries from cooling.

4. Physical damage: Physical damage to the battery, such as punctures or dents, can cause the battery to leak or catch fire. To prevent physical damage, batteries should be installed in a secure location that is protected from impact or damage.

5. Improper handling: Improper handling of lithium-ion batteries, such as dropping or crushing them, can also cause them to leak or catch fire.

When installed and maintained properly, lithium-ion batteries can provide a safe and reliable energy storage solution for solar applications.