Whether reducing the irregularity of your solar power system, or using solar power off-grid, solar storage is vital. But how do you decide between the most common options for solar storage, lead-acid or lithium-ion batteries? Let us examine the pros and cons of each choice, and determine which suits your needs best.
Understanding and Comparing Batteries
When comparing lead-acid and lithium-ion batteries, it is important to understand what you want from the batteries. Remember to consider:
- How much power can be stored (capacity)
- How much power can be used (power rating)
- How long will the battery last
- Battery cost
- The size and weight of the battery compared to its capacity and power rating (energy and power density)
- The amount of capacity available during use (Depth of Discharge)
- The battery’s ability to deal with high temperatures
Although both lead-acid and lithium-ion batteries have considerable diversity within their own categories, we can use these factors to generalize between two battery types.
Lead-acid batteries are robust, resilient and reliable, and have had over a century of use and design as a technology. They require little maintenance and have a long shelf life. And their biggest advantage is cost. Lead-acid batteries tend to be significantly cheaper upfront than lithium-ion, at around $125 per kWH. Unfortunately, the trade-off for the low cost is a shorter life span and a lower power density. Lead-acid batteries are big, bulky, and difficult to use outside of stationary contexts. Additionally, they require proper and careful disposal due to the toxic nature of lead. However, new designs allow for better performance, better energy output, and faster charge times, mediating some of the negative aspects of lead-acid batteries.
Lithium-ion batteries are a much newer technology, and they improve on lead-acid in multiple ways. Their largest advantage is a significantly improved lifespan, with faster charge and discharge times across their capacities. They have an improved Depth of Discharge and lose less capacity to irregular discharging. These batteries are lighter, more compact, easier to install and easier to dispose. Additionally, they perform better both in colder and hotter temperatures than lead-acid. Be prepared to pay for all of these advantages, however, as lithium-ion batteries cost much more upfront than lead-acid. Currently, lithium-ion batteries cost $273 per kWh. Yet, the longer lifecycle of this battery means that despite a higher initial investment, the battery may cost less over its lifecycle. Additionally, lithium-ion batteries require protection circuits and charge controllers, and the higher charge voltage of lithium-ion batteries require accommodation if your equipment is not adjustable or compatible.
Lithium-ion batteries clearly win when it comes to mobile applications, situations where full discharge occurs quickly, and in high-temperature environments. Yet lead-acid work well for low-cost or stationary systems. There is no clear winner, as the battery for you depends on the context and needs of your system. Naturally, things become more complicated when considering subtypes within each category, additional battery types, and individual manufacturers.
When picking the battery for your system, consider the your capacity, voltage, and life cycle needs, as well as costs both for initial investment and across the product’s lifespan. Use this information as a starting point for understanding those differences, and making your solar storage decisions.