Assembly Line

How car batteries are made

A car battery is lead plates in dilute sulfuric acid, a design that dates to 1859.

stations
6
things upstream
18
raw sources
8
steps from the ground
5

The short version

A lead-acid car battery is built from grids of lead alloy cast and pasted with lead paste, which is cured so it hardens. The pasted plates, separated by thin plastic sheets, are stacked into cells inside a plastic case and joined with lead straps. The case is filled with sulfuric acid and charged.

  1. Cast the grids

    Molten lead alloy is poured into molds that make a lattice, the grid that carries the current and holds the paste. Rough edges and casting gates are trimmed off once it cools.

    Goes in
    Lead

  2. Paste the grids

    Lead is ground into an oxidized powder and mixed into a paste with dilute sulfuric acid. The paste is forced into the openings of each grid.

    Goes in
    LeadSulfuric acid

  3. Cure the plates

    The pasted plates rest in a warm, humid chamber so the paste hardens and bonds to the grid.

  4. Stack the cells

    Positive and negative plates are interleaved, with a thin separator between each pair to stop them touching. Groups of plates are welded together with a lead strap.

    Goes in
    Polyethylene

  5. Seal into the case

    The cell stacks go into a plastic case, are connected in series, and the lid is heat-sealed on.

    Goes in
    Polypropylene

  6. Fill and charge

    Dilute sulfuric acid is added and the battery is charged for the first time. That charge converts the paste into lead dioxide on the positive plates and spongy lead on the negative ones.

    Goes in
    Sulfuric acidWater
End of the lineCar battery

Worth repeating

  • Gaston Planté's lead-acid cell was demonstrated in 1859, after Nicolas Gautherot noticed in 1801 that used wires gave a small secondary current.
  • When discharged, both plates turn into lead sulfate, and the acid turns mostly to water.
  • Battery makers treat their paste recipe as a top secret, since it holds the active material of the cell.

Back to the ground

Follow every input upstream and car battery starts as these 8 raw sources.

WaterLead oreSulfurAirCoalZinc oreNatural gasCrude oil

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Sources

Cite this page: "How car batteries are made." Assembly Line, 2026-11-03. https://assemblyline.org/make/car-battery

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