Lead-Acid Batteries

Conceivably the most popular application for lead-acid batteries is as the power source for the starter in an automobile. In stationary storage applications, lead-acid batteries are also used to provide uninterruptible power supply (UPS) service to datacenters and even island grid support for small scale distributed renewable energy applications. There are an estimated 95,000 lead-acid battery arrays deployed in the US at utility substations to provide blackout and black start grid support (Eyer & Corey, 2010).  First invented in 1859 by Gaston Planté, lead-acid batteries are the most prevalent form of energy storage today (EPRI, 2003).

               Lead-acid batteries consist of alternating plates of lead (Pb) and lead oxide (PbO₂), that form the electrodes. The electrodes are submerged in a liquid or gel electrolyte solution of sulfuric acid (H₂SO₄). During discharge the lead anode gives up electrons that the lead oxide cathode accepts. This creates the flow of electricity (Figure 1). During discharge both plates begin to accumulate lead sulfate (PbSO₄) (Hammack, 2012). 

Figure 1 basic diagram of a lead-acid battery during discharge.

While charging, the electron flow is reversed and sulfate returns to the electrolyte making it stronger and increasing the charge of the battery (EPRI, 2003). The overall chemical reaction is:

(EPRI, 2003)


The buildup of lead sulfate on the electrodes can limit the ability for the battery to recharge. For this reason lead-acid batteries to be used in deep discharge applications (common for energy storage) must be designed with larger electrodes that are spaced further apart and must also include a reservoir to capture sulfate debris (Hammack, 2012). This results in an increase in size and weight. The bulky nature of lead-acid batteries results in relatively low ratio of energy to size; i.e. a low energy density. This low energy density significantly reduces their appeal for grid scale energy storage (Baxter, 2006).

               Though lead is considered poisonous to humans, its density makes it easy to separate from other materials when a battery is recycled. This ability to easily isolate lead, coupled with the fact that lead-acid batteries are so pervasive, makes lead-acid battery recycling a profitable endeavor such that 96% of all lead-acid batteries are recycled. Even the spent electrolyte is recaptured through acid reclamation. 60% to 80% of each new battery contains recycled lead or plastic (US EPA, 2012).

Works Cited

Baxter, R. (2006). Energy Storage; A Nontechnical Guide. Tulsa, Oklahoma: PennWell Corporation.

EPRI. (2003). EPRI-DOE Handbook of Energy Storage for Transmission & Distribution Applications. Washington DC: EPRI, Palo Alto, CA, and the U.S. Department of Energy.

Eyer, J., & Corey, G. (2010). Energy Storage for the Electricity Grid: Benefits and Market Potential Assessment Guide. Albuquerque, New Mexico: Sandia National Laboratories.

Hammack, B. (2012, July 3). How a Lead-Acid Battery Works. Retrieved January 6, 2013, from Engineer Guy: http://www.youtube.com/watch?v=rhIRD5YVNbs&feature=youtube_gdata_player

US EPA. (2012, November 19). Batteries. Retrieved January 6, 2013, from US EPA: http://www.epa.gov/osw/conserve/materials/battery.htm