Knowing which battery type suits well your requirements, lifestyle, and wallet is essential if you’re thinking of adding batteries to your PV system, be it an on-grid or an off-grid system.
Therefore, if you are considering buying batteries, what technology should you employ? Should you invest in the most recent lithium-ion batteries? Or continue with the conventional lead acid batteries?
Let’s investigate this in detail and figure out.
Lead-Acid vs Lithium Ion
Lead acid battery
Anode and cathode in lead-acid batteries are made of lead or lead oxide, while sulfuric acid serves as the battery’s electrolyte. Flooded acid, gelled acid, and Advanced AGM (Absorbed Glass Mat) are the three major types of lead acid battery.
Lithium-ion battery
A lithium-ion battery is a kind of rechargeable battery which employs the reversible reduction of lithium ions for storing energy. It is the most common kind of battery for handheld gadgets and automobiles that run on electricity.
Which one to choose for your solar system?
Efficiency
Lead acid batteries are only 80 to 85% efficient based on their type and state. So, if you have a thousand watts of solar electricity flowing into the batteries, you will only have around 850 watts available after the batteries have been charged.
On contrary, lithium batteries possess a high efficiency of 95%. This means you will have 950 watts of power accessible in the same circumstance. A more efficient battery will charge more quickly. Based on the system’s layout, one may also need less solar panels, lower battery size, and a more compact standby generator.
Maintenance
Lead acid batteries have different upkeep needs based on their model. They need to be maintained by periodically having their water levels topped up with distilled water and having the terminals cleaned to avoid corrosion. A lack of ventilation might cause the batteries to overheat and fail. To avoid sulfation, it is also important to check the battery wires and charge level.
Now, you may wonder how difficult it is to care for lithium batteries. To put it simply, there is no maintenance required. They need little upkeep if they are placed properly and kept in a suitable environment (usually between 10°C to 30°C). A battery management system (BMS) is built into all lithium units, and it keeps tabs on the condition of battery cells in terms of heating, load, and lifespan. To sum up, modern lithium batteries need zero maintenance, in contrast to the majority of new VRLA lead acid battery packs.
Depth of discharge
The depth of discharge refers to the extent to which a battery may be emptied of its energy supply without being damaged. While it is a common practise to drain a lithium-ion battery to 85% or higher in a single cycle, lead acid batteries should never be discharged to below 50% to avoid premature failure. Lithium-ion batteries offer a greater effective capacity as compared to lead acid alternatives due to the greater depth of discharge available.
Lifespan
Like solar panels, batteries lose performance and efficiency over time. One “cycle” consists of completely draining a battery to power your equipment, and then fully charging it using renewable energy sources or the grid. Lithium-ion batteries have been shown to outlast lead acid batteries by a significant margin, with some studies finding that they may withstand up to ten times as many charges and discharges before showing signs of wear.
Weight
When compared to lead-acid batteries, lithium-ion batteries are much lighter. Lithium batteries have a far better energy density than lead-acid ones, which means they can store more energy in the same amount of space. If you’re limited on mounting options for your battery pack, this might be a huge help. The higher energy density of lithium batteries allows them to be packed into smaller places.
Environmental sustainability
In terms of their impact on the planet, lead acid batteries fail to impress. Lead acid batteries need more raw materials than lithium-ion batteries to store the same quantity of solar energy. Of course, everyone knows that increasing the use of raw materials will lead to a larger carbon footprint. Also, producing lead acid is an extremely energy intensive process. Even making the battery itself consumes a lot of energy. This results in massive volumes of pollutants being discharged into the environment.
Lead acid batteries now have a better recycling rate than lithium-ion batteries, which bolsters their reputation as environmentally friendly. Lithium-ion batteries aren’t recycled as often as lead acid ones since the technology is still relatively new and the recycling machinery is still being developed, making it expensive. However, recycling rates for lithium-ion batteries are predicted to swiftly overtake those of lead acid batteries as demand and industry for these products continue to rise. The use of recovered lithium is far more cost-effective than mining for more, which means that lithium-ion battery recycling may soon overtake lead acid.
Cost
When compared with lithium-ion batteries, lead-acid batteries are more affordable and simpler to install. lithium-ion batteries are two times more expensive than lead-acid batteries of the same capacity. The initial capital cost of the lead-acid battery is lower than that of the lithium-ion battery, making it more suited for use in PV stand-alone invertors than the lithium-ion battery. However, lithium-ion batteries offer significant benefits over lead-acid battery technology, including increased energy density, lower maintenance requirements, lower environmental impact, and a longer service life.
Head-to-head comparison
| Parameters | Lithium Ion Battery
|
Lead Acid battery |
| Material | Lithium Iron Phosphate | Lead acid |
| Life (years) | 15 | 8 |
| Cycle times | 4000 cycles | Around 1300 cycles |
| Weight | Light weight | 3x the weight of Lithium-ion battery |
| Environmental impact | Positive | Negative |
| Charging time | Fast | Slow |
| Cost | More expensive | Less expensive |
| Efficiency | High | Low |
| Charge/discharge temperature | 0°C – 60°C/ -20°C – 60°C | 0°C – 45°C/-20°C – 45°C |
| Warranty | 3 years | 1 year |
Conclusion
The argument for lithium batteries to replace conventional household batteries, at least eventually, is strong. Lithium has several benefits compared to other materials, including a lower weight, better efficiency, and deeper discharge, but its initial cost is higher. They may soon be ahead of the competition in this area as well since the price of lithium batteries is expected to drop dramatically over the next decade. Lead acid batteries, and especially the VRLA variant, which use technology that has been perfected over the last 150 years, are still a good option for off-grid applications. What you choose will depend on your needs, preferences, and financial situation. Consulting a professional with knowledge of battery systems may help you determine which options provide the most advantages for your needs.