Investing in solar is smart; pairing solar with a lithium battery storage unit is even smarter. While lithium batteries tend to be a higher initial investment compared to lead-acid batteries, their superior performance and longevity make them an ideal choice for off-grid as well as grid-tied applications.
When selecting a battery to complement your solar system, understanding the advantages that lithium batteries provide over lead-acid batteries is essential.
Here are some key advantages lithium batteries have over lead-acid for storing solar energy:
- Lithium batteries are more efficient
- Lithium batteries last longer
- Lithium batteries are cost-effective
- Lithium batteries require zero maintenance
Lithium Batteries Are More Efficient
According to the Institute of Electrical and Electronics Engineers, the roundtrip efficiency of lead-acid batteries is around 70% to 80%. In other words, even if you fully charge a lead-acid battery, you will lose 20 to 30 percent of that energy during the charge and discharge process. So if you purchase a lead-acid battery with a nameplate capacity of 10 kWh, your usable capacity will only be 7 or 8 kWh due to energy losses. In a world where inverters and charge controllers are reaching efficiencies in the high 90s, it is highly desirable that the energy storage system is also highly efficient in order to minimize unnecessary energy losses. Fortunately, most lithium batteries offer 95 percent efficiency and above, with the highest quality lithium batteries providing 99 percent efficiency.
Harvesting all the energy from your renewable energy system is another way in which lithium batteries outperform lead-acid batteries. The low charge acceptance of lead-acid batteries often means that your inverters and charge controllers must reduce the energy that they can harvest so as to not exceed the low-charge currents that lead-acid batteries can accept. Lithium batteries, on the other hand, do not have such a disadvantage since it can be charged at the 1C rate. For example, if your lithium battery has a capacity of 100 Ampere-hours, you can charge your battery with 100A.
Lithium Batteries Last Longer
The cycle life of a battery, or the number of charge and discharge cycles that a battery can complete before the performance begins to deteriorate, is an important parameter in batteries since it determines how long your batteries will last. This is another area where lithium batteries outperform lead-acid batteries since they often last 20 times longer than lead-acid on average. If you discharge your lead-acid battery 100% of its capacity it will deliver about 400 to 600 cycles. A lithium battery on the other hand will deliver 8,000 cycles under the same conditions. This is due in part to the fact that most lead acid batteries are not designed to be deeply discharged and can actually be damaged when discharged more than 50 percent of their total capacity.
Another reason that lead-acid batteries do not last as long is their high sensitivity to being undercharged. If a lead-acid battery is chronically under-charged, it will suffer significant damage and its lifespan can be reduced by up to 80%. This is important since renewable energy sources are naturally intermittent with the end result of the batteries being operated at partial states of charge. With lithium, you do not need to worry about leaving your energy storage system in partial states of charge (e.g., 40 percent, 65 percent - anything other than 100 percent) since cycling lithium batteries at partial states of charge does not harm them in any way.
Lithium Is Cost Effective
With lead-acid batteries, you often have to significantly over-size your battery bank to limit how much you discharge your batteries. As mentioned above, most lead-acid battery manufacturers recommend against discharging their batteries beyond 50 percent. This means that your battery bank has to be 2x larger than it really needs to be to meet your actual energy requirements. Since lithium batteries allow you to use 100% of their nameplate capacity without sustaining any damage, you will save on costs due to not needing to oversize your battery bank.
Additionally, all batteries experience a decrease in both usable capacity and efficiency in temperatures below 32°F. However, lead acid batteries are the most impacted by cold temperatures, as they provide only 70 to 80 percent of their rated capacity at 32°F. Alternatively, lithium batteries can operate with very little losses at this temperature, providing 95 to 98 percent of their rated capacity. The large capacity loss that lead-acid batteries experience in cold weather results in lead-acid battery owners needing to again invest in oversizing their energy storage systems, which can be costly.
Lithium Batteries Require Minimal Maintenence
Lead-acid batteries need to be carefully monitored and maintained. If water levels drop too low, you have to refill them or face significant damage and hazard risk. Many lead acid batteries also produce hydrogen sulfide gas, which is flammable and poisonous, when they are overcharged. Lithium batteries, conversely, require zero maintenance after installation. For example, lithium batteries that use a sophisticated internal Battery Management System (BMS) prevent the possibility of overcharging or discharging. Additionally, lithium batteries do not release any toxic gases as many lead-acid batteries do. While you should monitor any battery you purchase – even lithium – upkeep is reduced significantly with a lithium-based solution.
Lithium batteries are also very space-efficient due to their much higher energy density, or the amount of energy they are capable of storing in a system per unit volume. For example, RELiON lithium batteries typically weigh one-third less and provide up to 50 percent more energy than traditional flooded AGM, or GEL lead-acid batteries. In other words, lithium batteries provide more usable energy in a much smaller and lighter package. If you’re setting up your solar application and find yourself running out of room for batteries, choose lithium batteries to reduce your size and weight constraints considerably.
Compared to lead-acid, lithium offers a more compelling energy storage option in nearly every situation. If you’re unsure about your solar power storage needs, contact us so we can help determine the perfect fit for your application.
Interested in more? Get all the technical specifications you need to find the right lithium solar battery for your application.