How do lithium-ion and lead-acid batteries compare?
Both ion and lead-acid batteries store energy efficiently, but each has unique advantages and disadvantages. Here are some important comparison points to consider when deciding on battery type:
cost
One area where lead-acid batteries seem to have an advantage over lithium-ion batteries is their cost. Lead-acid battery systems can cost hundreds or thousands of dollars less than similarly sized lithium-ion battery systems - lithium-ion batteries currently cost from $5,000 to $15,000 (including installation), and the range may be higher or Lower, depending on the size of the system you need.
While lead-acid batteries are generally less expensive to purchase and install than lithium-ion batteries, the lifetime value of lithium-ion batteries is comparable. Below, we outline other important characteristics of each battery type to consider and explain why these factors contribute to the overall higher value of lithium-ion battery systems.
capacity
A battery's capacity is a measure of how much energy the battery can store (and ultimately release). While capacity figures vary by battery model and manufacturer, lithium-ion battery technology has been well proven to have significantly higher energy density than lead-acid batteries. This means more energy can be stored in the same physical space in a lithium-ion battery. Because lithium-ion technology can store more energy, it can release more energy to power more appliances for longer.
Discharge depth
A battery's depth of discharge is the percentage of the battery that can be safely drained of energy without damaging the battery. While it is normal to use 85% or more of a lithium-ion battery's total capacity in a single cycle, lead-acid batteries should not be discharged more than approximately 50%, as doing so will negatively affect the battery's service life. The superior depth of discharge of lithium-ion technology means that lithium-ion batteries have a higher effective capacity than lead-acid batteries, especially given the higher energy density of lithium-ion technology mentioned above.
efficiency
Like solar panel efficiency, cell efficiency is an important metric to consider when comparing different options. Most lithium-ion batteries are 95% or more efficient, meaning that 95% or more of the energy stored in a lithium-ion battery can actually be used. In contrast, lead-acid batteries are closer to 80 to 85 percent efficient. Batteries with higher efficiency charge faster, and similar to depth of discharge, increased efficiency means the battery has a higher effective capacity.
life
Batteries are also similar to solar panels in that they degrade over time and become less effective as they age. Discharging the battery to power your home or appliances and then charging it using solar power or the grid counts as one "cycle." Figures vary from study to study, but lithium-ion batteries typically last several times longer than lead-acid batteries, giving lithium-ion products a longer effective life.
