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An A – Z of Batteries – Q, R and S

Written on August 25, 2016 at 9:10 am

In this article we continue our A -Z of all things battery with the letters Q, R and S, taking a look at quiescent voltage, reverse charging and sulphuric acid as we continue to explain everything you ever needed to know about the automotive battery.


Q is for Quiescent Voltage

Quiescent Voltage

The quiescent voltage is the theoretical open circuit voltage of a cell in a 12v battery at full charge. As a 12V vehicle battery is generally comprised of 6 cells, the value per cell if fully charged will be 2.10V, which multiplied by six gives the total voltage of the battery. If a battery is not fully charged, the quiescent voltage will fall, making it harder for the battery to deliver the voltage needed to start the engine. Generally speaking, reading the voltage of a single cell will be a good indicator of the overall battery health. A fully working battery in a correctly functioning system will charge during vehicle use in order to maintain the correct level of power.


R is for Reverse Charging

Reverse Charging

Apart from their ability to deliver the high level of surge power needed to start an engine, one of the key reasons that lead acid batteries have become such a vital component of the modern automotive vehicles is the possibility to recharge them during the normal operation of the vehicle, in a process known as reverse charging. As a general definition, reverse charging is the process by which an electrical battery can be charged, discharged into a load, and recharged many times. It is this process that has led to the lead acid battery frequently being referred to as an “accumulator”, as it accumulates and stores energy through a reversible electrochemical reaction.

As long as the battery is properly looked after, this process will be able to occur for a large number of cycles, hence the long life of a typical car battery. If the battery is not properly looked after or is too old, however, the conditions inside will deteriorate and eventually prevent reverse charging from being effective. As a rule, it is generally recommended to replace a car battery after about five years of standard use in normal conditions.


S is for Sulphuric Acid

Sulphuric Acid

Sulphuric acid, the liquid substance frequently referred to as battery acid, is the key to how an automotive battery works. A car battery consists of a number of cells, each of which houses two electrode plates – one negative (lead), one positive (lead dioxide) – suspended in a solution of sulphuric acid (PbSO4). The discharge process is driven by the conduction of electrons from the negative plate back into the cell at the positive plate in the external circuit, and the charging process by the reverse. At full discharge, the electrolyte loses much of its dissolved sulfuric acid and becomes primarily water.

Whatever the vehicle, buying the correct battery and maintaining it properly will guarantee that it lasts as long as possible. At Manbat, we stock a vast range of vehicle batteries for cars, motorcycles and LCV’s , as well as industrial and marine applications. With twelve branches nationwide stocking a full stock of Varta, Numax and Lucas batteries to cover almost every vehicle part number available, you can be sure we have the battery you need, when you need it. To find out more, fill in our online contact form or give us a call on 01743 218500.

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