# Lead-Acid Battery > Electricity kept in lead and acid - Date: 1859 - Era: Industrial age - Domain: [Electricity & Electronics](https://lastcodex.org/en/domains/electricity/) - Rebuild stage: IV (Science & industry) - Difficulty: 4/5 - URL: https://lastcodex.org/en/inventions/lead-acid-battery/ A lead-acid battery stores electricity in plates of lead and lead dioxide standing in dilute sulfuric acid, gives it back as current, and can be recharged hundreds of times. Gaston Planté built the first cell in 1859; with Camille Faure's pasted plates of 1881 it became an industrial product, and it still starts most of the world's cars. ![Lead-Acid Battery · Electricity kept in lead and acid](https://lastcodex.org/_astro/plate.Vip0wrOU_Z2lWarr.webp) ## Legend 1. Positive plate (lead dioxide) 2. Negative plate (spongy lead) 3. Separator 4. Electrolyte (dilute sulfuric acid) 5. Lead strap and terminal post 6. Glass jar ## What it is A lead-acid battery stores electricity as chemistry and gives it back as current, hundreds of times over. Each cell holds lead plates in dilute sulfuric acid and gives about two volts. A car battery is six cells in one case, connected in series for twelve volts. The French physicist Gaston Planté built the first rechargeable cell in 1859: it could be charged again by sending current back through it. In 1881 Camille Faure changed the way the plates were prepared, coating them with lead oxide, so that cells were ready sooner and could be made in factories. The reaction inside is the one Planté used. ## How it works ![A lead grid half filled with brown paste, a wooden spatula beside it](https://lastcodex.org/_astro/v2.BfC0ld69_Z1tmDsM.webp) _A pasted plate: lead oxide paste pressed into a cast lead grid, which holds it in place._ The positive plates (1) carry lead dioxide, a dark brown powder. The negative plates (2) carry spongy grey lead, full of pores so the acid reaches as much metal as possible. Separators (3) keep them apart, and the electrolyte (4), sulfuric acid diluted in water, fills every gap. During discharge the lead and lead dioxide on the plates react with the acid and turn into lead sulfate, while the lead grids carry the current. Electrons leave the negative plate and reach the positive one through the outside circuit, running the lamp or motor on the way. The reaction consumes acid and makes water, so the electrolyte thins as the cell empties: in a starter battery its specific gravity (density relative to water) falls from about 1.265 to about 1.12. Charging runs the reaction backwards. Current from a generator, a solar panel or a mains charger turns the sulfate back into lead and lead dioxide, and the acid returns to the liquid. Near the end, little sulfate is left and part of the current splits water instead: hydrogen bubbles off the negative plates, oxygen off the positive ones. This gassing is why flooded cells lose water and charging rooms need fresh air. Capacity is counted in ampere-hours (Ah): a 60 Ah battery supplies 3 A for about 20 hours, the usual rating period, and less if drained faster. Sulfate left on a discharged plate for weeks can grow into hard crystals that ordinary charging may not reverse, and deep discharges wear out the active material. In one Battery University comparison, a starter battery fully emptied each time lasted 12 to 15 cycles, against 130 to 150 when only 30% of its charge was used. ## How to build Making cells means handling molten lead and strong acid, so this section covers choosing, charging and looking after a bought battery. **Size it for the load.** A cabin runs three 5 W LED lamps for five hours and a 10 W radio for three hours each day: 75 + 30 = 105 watt-hours, about 9 Ah at 12 V. Allow two days without charging (18 Ah) and use no more than half the capacity: you need at least 36 Ah. Choose a 40 to 50 Ah deep-cycle battery: cold also cuts capacity. **Charge at the right voltage.** Use a charger made for that battery's voltage and type (flooded, AGM or gel) and follow the maker's charging profile. At about 25 °C a 12 V flooded battery is typically charged up to between 13.8 and 14.7 V, depending on the model, then held at about 13.5 V; good chargers adjust the charging voltage to the battery's temperature. With a solar panel, put a charge controller between panel and battery. Whatever the charging source, fit a fuse sized for the cable close to the battery's positive terminal, and protect each circuit that feeds a load. Recharge soon after use; never charge a frozen battery. ![A battery hydrometer: glass tube with a rubber bulb and nozzle, a weighted glass float inside](https://lastcodex.org/_astro/v1.D1vu7bvy_Z1f1Xgu.webp) _Squeeze the bulb, draw acid from a cell and see how high the float rides: the denser the acid, the fuller the cell._ **Check the state of charge.** Let the disconnected battery rest at least four hours, ideally a day, then measure across the terminals. As an example, one starter battery at 26 °C after a day's rest reads about 12.65 V when full and about 11.9 V when flat; every model differs, so use the maker's table. With flooded cells, a hydrometer reads each cell: on that same battery, about 1.265 when full and about 1.12 when flat. **Top up with distilled water only.** Add distilled water to the mark after charging, once the battery has cooled; if the plates are uncovered before charging, add just enough to cover them first. Never add acid. Sealed AGM and gel batteries need no water. **Clean, store, recycle.** Brush terminal crust off with baking soda in water, keeping it out of the cells, then dry and grease the posts. Store a battery charged, cool and dry; check its voltage every month or so and recharge it before it falls below about 12.3 V, or the maker's threshold, and at least every six months. Take a dead one back to a dealer or a collection point. > **Safety.** Battery acid burns skin and eyes: wear goggles and acid-resistant gloves, and after a splash rinse with running water for at least 30 minutes and get medical help. Charging releases hydrogen, which a spark or flame can ignite: charge in a ventilated place, never smoke nearby, and switch the charger off before fitting or removing its clips. In a car, disconnect the cable bolted to the bodywork first (on almost every car the negative) and reconnect it last. A short circuit drives hundreds of amperes and can melt a spanner: use insulated tools and take off rings and watches. A car battery can weigh 15 kg or more: keep it upright and lift with your legs. Lead is toxic: wash your hands after handling, never burn a battery or break its case open (on a flooded battery, remove only the filler caps), and keep batteries away from children. ## History and evolution Planté showed his cells to the French Academy of Sciences in 1860: lead sheets separated by rubber strips in dilute acid, formed by reversing the current again and again until their surfaces turned porous. ![A row of glass-jar cells on a wooden stand, joined in series by lead straps](https://lastcodex.org/_astro/v3.BUBCqaot_Z75won.webp) _Racks of glass cells kept lighting stations and telephone exchanges going through peaks and breakdowns._ While charging meant using up primary cells, the batteries stayed in laboratories; dynamos changed that in the 1870s. Faure's paste replaced months of forming with one charge of about sixty hours. Power stations of the 1880s and 1890s kept banks of cells across their mains to take the evening peak. From about 1893 telephone exchanges fed subscribers' lines from a central battery. Around 1900 electric cars, most on lead-acid batteries, made up about a third of the vehicles on American roads. Charles Kettering's electric starter, fitted to the 1912 Cadillac, did away with the hand crank; as it spread to other makes, the starting battery became standard equipment. In the United States about 99% of lead batteries are recycled, and new ones contain more than 80% recycled material. ## Key figures - Voltage of one cell: About 2.1 V at rest when fully charged; six cells in series make a 12 V battery - Acid specific gravity: About 1.265 when charged, about 1.12 when discharged (starter battery, after a 24-hour rest) - Charging voltage: 2.30–2.45 V per cell, then about 2.25 V per cell to hold it full - Recycling: 99% of lead batteries recycled in the United States (industry study, data to 2018) ## Requires - [Battery](https://lastcodex.org/en/inventions/battery/): Chemistry that pushes a current (1800) - [Electric Generator](https://lastcodex.org/en/inventions/generator/): Motion turned into current (1831) ## Leads to - [Wind Turbine](https://lastcodex.org/en/inventions/wind-turbine/): Wind turned into electricity (1887) ## Sources - [Accumulator (1911 Encyclopædia Britannica)](https://en.wikisource.org/wiki/1911_Encyclop%C3%A6dia_Britannica/Accumulator), Encyclopædia Britannica, 11th edition, via Wikisource - [One of the First Rechargeable Batteries, about 1860](https://collection.sciencemuseumgroup.org.uk/objects/co36401/one-of-the-first-rechargeable-batteries-about-1860-lead-acid-rechargeable-batteries), Science Museum Group - [Planté Battery – 1859](https://nationalmaglab.org/magnet-academy/history-of-electricity-magnetism/museum/plante-battery-1859/), National High Magnetic Field Laboratory - [BU-201: How does the Lead Acid Battery Work?](https://batteryuniversity.com/article/bu-201-how-does-the-lead-acid-battery-work), Battery University (Cadex Electronics) - [BU-403: Charging Lead Acid](https://batteryuniversity.com/article/bu-403-charging-lead-acid), Battery University (Cadex Electronics) - [BU-903: How to Measure State-of-charge](https://batteryuniversity.com/article/bu-903-how-to-measure-state-of-charge), Battery University (Cadex Electronics) - [BU-804b: Sulfation and How to Prevent it](https://batteryuniversity.com/article/bu-804b-sulfation-and-how-to-prevent-it), Battery University (Cadex Electronics) - [Battery Charging – Industrial Lead-Acid Batteries](https://ccohs.ca/oshanswers/safety_haz/battery-charging.html), Canadian Centre for Occupational Health and Safety - [Charging safely](https://www.safetyandhealthmagazine.com/articles/charging-safely-2), Safety+Health, National Safety Council (NIOSH advice) - [Lead Battery Industry Issues New National Recycling Rate Study](https://batterycouncil.org/news/lead-battery-industry-issues-new-national-recycling-rate-study/), Battery Council International - [The History of the Electric Car](https://www.energy.gov/articles/history-electric-car), U.S. Department of Energy - [Switches, PBXs and Central Offices, chapter 12: power plants](https://www.telephonetribute.com/switches_survey_chapter_12.html), TelephoneTribute.com - [Lead poisoning and health](https://www.who.int/news-room/fact-sheets/detail/lead-poisoning-and-health), World Health Organization - [Lead–acid battery](https://en.wikipedia.org/wiki/Lead%E2%80%93acid_battery), Wikipedia - [Lead Acid Batteries](https://www.pveducation.org/pvcdrom/batteries/lead-acid-batteries), PVEducation (C. Honsberg and S. Bowden) - [Performance Testing Lead-Acid Stationary Batteries: Myths, Misunderstandings and Mistakes (Battcon 2016)](https://www.vertiv.com/48dea9/globalassets/documents/battcon-static-assets/2016/performance-testing-lead-acid-stationary-batteries-myths-misunderstandings-and-mistakes.pdf), R. Tressler, Vertiv Fact-checked on 2026-10-14. --- The Last Codex · https://lastcodex.org/en/inventions/lead-acid-battery/ · © The Last Codex. Texts, plates and figures: CC BY-NC-ND 4.0.