There are more differences to Lithium and Lead acid batteries than similarities. Everything from weight to battery efficiency to life cycle is so different it’s amazing that they are even compared. Even though lead acid batteries have been a common way to store electrical energy for decades, advancements in lithium technology make using lead acid batteries difficult to justify.
How is lithium different from the lead acid batteries that consumers are used to? The difference in weight is immediately noticeable. Lithium batteries contain no lead or fluid, which means significant weight savings. The absence of acid also means they don’t present an environmental hazard if they are tipped over or broken.
The difference in price between lithium and lead acid technologies is significant, but is there a good reason for that? Depending on the type of lithium technology, manufacturing can be very labor intensive. Many lithium manufacturers spend a lot of time ensuring that their quality control is very high, opposed to the high volume and low quality control lead acid manufacturing process. However, most of the difference in cost in lithium technology is due to the high power density of the batteries. Many lead acid batteries are only good for 300-600 cycles, while lithium technology allows for 2000-3000 cycles at a deeper depth of discharge.
One of the most significant differences between lithium and lead acid is how the battery performs during each cycle. A typical lead acid battery is rated to 50% depth of discharge, but the voltage drops during a discharge cycle. Lithium batteries are rated to 80% depth of discharge but will hold a consistent voltage throughout the entire cycle, putting out significantly more power in the same time period.
Lead acid batteries are also 25-40% efficient while lithium technology is 95-98% efficient. This means that lithium technology is much more efficient at moving energy in and out of the battery than a comparable lead acid. It also means that with two batteries that are rated at the same voltage and amp hours, the lithium battery will have a longer run time because of these factors.
Lead acid technology is the most cost effective energy storage system in terms of up front cost but when you combine low efficiency with less available power, the long-term cost of ownership cannot compete with lithium technology. The power density and efficiency of lithium makes it an easy choice compared to lead acid but it is important to remember that like lead acid technology, not all lithium is created equal.