---
title: "What is a Car battery made of?"
description: "Lead and lead dioxide plates in dilute sulfuric acid, in a polypropylene case — mostly lead, by weight. Every component, the material it uses, and the constraint tha"
url: https://atoneplace.net/made-of/car-battery/
site: "At One Place"
---

# What is a Car battery made of?

**What is a Car battery made of?: Lead and lead dioxide plates in dilute sulfuric acid, in a polypropylene case — mostly lead, by weight.**

A lead-acid battery is roughly 60-70% lead by mass, and it is the most recycled consumer product in the developed world — recovery rates above 95% are normal, because the lead is valuable, the collection route through garages is well established, and disposal is tightly regulated. The failure mode most owners meet is sulfation: leaving a battery discharged lets soft lead sulfate recrystallise into a hard form that will not convert back, permanently losing capacity. That is why a car left standing for months needs a maintenance charger, and why jump-starting a deeply flat battery often only buys a few days.

## Component by component

*Every material is a choice, and the third column is the constraint that drove it.*

| Part | Material | Why that material |
| --- | --- | --- |
| positive plates | lead dioxide paste on a lead alloy grid | The lead-acid couple gives about 2.1 V per cell and can deliver hundreds of amps briefly, which is exactly what a starter motor needs. |
| negative plates | porous "sponge" lead | The high surface area lets the reaction run fast enough for cranking current without the plates overheating. |
| electrolyte | sulfuric acid diluted to roughly 35% by weight | The acid is a reactant, not just a conductor, so a discharged battery genuinely has weaker acid — which is why it freezes more easily. |
| separators | microporous polyethylene, or a glass fibre mat in AGM batteries | They stop the plates touching while letting ions through; the AGM mat also holds all the acid, so the battery cannot spill. |
| case | polypropylene | It resists sulfuric acid indefinitely, survives underbonnet heat and is easy to recycle alongside the lead. |

## Other cars and driving objects

- [Car tire](https://atoneplace.net/made-of/tire/) — Several different rubber compounds reinforced with steel and textile cord — closer to a composite than to rubber.
- [Airbag](https://atoneplace.net/made-of/airbag/) — A coated nylon bag inflated by a small solid-propellant gas generator in about thirty milliseconds.
- [Brake pad](https://atoneplace.net/made-of/brake-pad/) — A friction compound of fibres, fillers and resin, moulded and bonded onto a steel backing plate.
- [Windshield (windscreen)](https://atoneplace.net/made-of/windshield/) — Two sheets of ordinary glass laminated to a tough plastic interlayer, which is what stops it falling out.
- [Spark plug](https://atoneplace.net/made-of/spark-plug/) — A ceramic insulator carrying a centre electrode of nickel, platinum or iridium inside a steel shell.
- [Seatbelt](https://atoneplace.net/made-of/seatbelt/) — Woven polyester webbing designed to stretch a controlled amount, plus a locking retractor and a pyrotechnic pretensioner.

## Common questions

### What is a Car battery made of?

Lead and lead dioxide plates in dilute sulfuric acid, in a polypropylene case — mostly lead, by weight.

### What is the positive plates of a Car battery made of?

Lead dioxide paste on a lead alloy grid. The lead-acid couple gives about 2.1 V per cell and can deliver hundreds of amps briefly, which is exactly what a starter motor needs.

### What is the negative plates of a Car battery made of?

Porous "sponge" lead. The high surface area lets the reaction run fast enough for cranking current without the plates overheating.

## Related pages

- [Car tire](https://atoneplace.net/made-of/tire/)
- [Airbag](https://atoneplace.net/made-of/airbag/)
- [Brake pad](https://atoneplace.net/made-of/brake-pad/)
- [Windshield (windscreen)](https://atoneplace.net/made-of/windshield/)
- [Spark plug](https://atoneplace.net/made-of/spark-plug/)
- [Seatbelt](https://atoneplace.net/made-of/seatbelt/)
- [Pencil](https://atoneplace.net/made-of/pencil/)
- [Tennis ball](https://atoneplace.net/made-of/tennis-ball/)
- [Banknote](https://atoneplace.net/made-of/banknote/)
- [Golf ball](https://atoneplace.net/made-of/golf-ball/)
- [Paper](https://atoneplace.net/made-of/paper/)
- [Glass](https://atoneplace.net/made-of/glass/)

## Sources

- Typical range compiled from manufacturer specifications — At One Place (/about/)