The anatomy of a battery

The anatomy of a battery

Of the myriad of commercial vehicle (CV) components, the humble battery is possibly one of the most difficult to evaluate in terms of its quality, as visually, whether premium or substandard, they all look virtually identical. However, with batteries, the phrase “you get what you pay for” is particularly pertinent, because it’s what’s in the case that makes all the difference.

Although absorbed glass mat (AGM) and enhanced flooded battery (EFB) batteries are very much in the spotlight, the traditional starter, lighting & ignition (SLI) battery is still by far the most common aftermarket replacement, not just here in Ireland, but throughout Europe.

From the outset, it is worth clearing up a point of confusion, which is, whether SLI, AGM or EFB, all are lead-acid batteries and the underlying principle remains the same, as within the case are situated six ‘cells’ that each provide 2.1-volts and which, joined in series, provide the 12.6-volts that generally constitute a ‘fully charged’ 12-volt battery.

The anatomy of a battery Lucas EFB

In a typical SLI battery, lead and sulphuric acid/de-ionised water solution (the electrolyte) make up the primary elements within the case, which must be nonconductive (to electricity) and naturally, acid resistant. Each cell consists of lead and lead oxide electrodes in the form of plates, the number, design and quality of which define the performance of the battery.

The lead provides the negative electrode, the lead oxide the positive, which when submerged into the electrolyte causes a chemical reaction that ultimately produces electrons that provide the battery’s power, directed to the conductive positive and negative terminals.

The chemical reaction produced within the cells slowly causes the lead and lead oxide to combine with the acid to become lead sulphate, which gradually reduces the electrons that can be produced and therefore, the efficiency of the battery, as it ‘discharges’. However, when the battery is charged, the lead sulphate is restored back to lead on the negative plates and lead oxide on the positive plates.

When it comes to AGM batteries, the fundamentals remain common to their SLI cousins, apart from the fact that they are termed valve regulated lead-acid (VRLA) batteries because they are sealed and recirculate the hydrogen/oxygen gas produced during recharging within the case, rather than allowing it to escape through a vent and the electrolyte liquid is absorbed into a micro-fibre mat, as opposed to being free to move.

The pure-lead plates within an AGM battery are very thin and, as they are separated by a layer of micro-fibre mat that is also very thin, it is possible to fit several plates into each cell, providing a greater total lead surface area, which reduces internal resistance and boosts the battery’s efficiency.

Premium quality CV batteries such as the Lucas and Numax ranges offered by ECOBAT Battery Technologies (EBT) have the added benefit of encompassing ‘punched plate’ technology on their negative electrodes, which is specifically designed to further increase the efficiency when it comes to the transfer of current and subsequently this reduces power loss.

As the largest lead smelter and therefore the principle supplier of lead ingots to the world’s battery manufacturers, ECOBAT Technologies is also at the forefront in the development of lead and lead alloys. This leading position allows it to engineer the formulation of these key elements to ensure the optimum performance characteristics of the battery.

This area of expertise is also of direct benefit to EBT customers as it is uniquely placed to specify the most appropriate of these key elements when drawing up the specification for both the Numax and Lucas CV battery programmes.

Tags: battery, EFB, AGM, ECOBAT


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