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How is a car battery made? Understanding lead-acid batteries

To many automotive enthusiasts, there’s always been a bit of mystery about the humble lead-acid battery found in our vehicles. Sure, most of us probably know the basics – like it contains acid, which creates electricity through a chemical reaction of some sort – but more than likely we’ll happily leave things there and not give our batteries further thought. That is, until we’re stuck on the roadside with a flat battery.

But understanding how batteries are made, plus how they should be used and maintained is absolutely vital to getting the longest life and best performance out of it. Luckily for you, Australian battery manufacturer Century Batteries have produced this handy overview of how a lead acid battery is manufactured.

As you’ll see in the video above, the initial process begins with the manufacturing of battery grids, which are stamped out of a continuous stip of lead. The purpose of these grids are to conduct the electrical current and to provide a structure for the active material to adhere to.

Next, a paste mixture consisting of lead oxide, sulfuric acid and water is applied to both sides of the grids. Expander material made of powdered sulfates is added to the paste to produce negative plates. From there, the fully pasted plates will need to be cured – a process which takes place in a warm temperature and humidity controlled environment for two to four days. During this process, the crystallization growth occurs which binds the paste to the grids.

Once the plates are ready, they are then stacked alternatively (positive, negative, positive, etc) with separators placed between them. The role of the separators are to literally separate the individual plates from each other, to prevent short circuits yet still allow electrical current to flow between. All the negative plates are connected together, and likewise all the positive plates are too – creating a single 2-volt battery cell.

The cells are then properly oriented and inserted into the battery case. The required voltage of the battery will determine how many 2-volt cells are required – so a typical 12-volt battery will require six of these 2-volt cells to be dropped into the case and welded together in a series.

Once all of the battery cells are in place and welded together, the top cover can be permanently heat sealed to the top of the battery. The top cover contains the connected elements, and the terminal posts are formed outside creating an acid tight seall.

From there the battery can be given an initial fill of sulfuric acid (or “electrolyte”) and given a formation charge. During this formation charging period, the battery is connected to an electrical source and charged for 24 – 32 hours depending on the battery type and size.

Once fully formed, the battery is drained of it’s electrolyte and then filled with higher strength acid, the sealing process is completed and following various quality checks, cleaning and labelling – it is ready for service!

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