In recent years, batteries have emerged as the weak point in all kinds of different applications, for example motor vehicles, ground conveyors, and working or lifting platforms. Incorrect battery maintenance, unsuitable charging procedures or changes in user behaviour represent the main problems; these are discussed in greater detail below.
This state is typical in batteries that are only charged using an alternator or an unregulated charger. Using either of these two charging methods it is virtually impossible to achieve over 80% charge because the charging time required for a fuller charge is far too long. Now, if these batteries are never charged fully, then their performance and capacity will be greatly reduced.
Changes in driving habits in recent years (more short journeys) often result in a starter battery being only partially charged. At the same time, the electrical consumers in a vehicle take more and more current out of the battery. These developments mean that a battery will require ever-more frequent external charging.
When a battery is already fully charged and more energy is fed into the battery, this has the effect of causing more intense gassing and an increase in water consumption. The battery will continue gassing until either the charger is switched off or there is no water left. As the temperature increases, the chemical processes in the battery speed up. The gassing voltage drops, and if the charging voltage is not adjusted to take account of the temperature change, then the battery will be overcharged. The danger here is that the grid may become corroded and the battery may age rapidly. If, for instance, the temperature is increased by 10°C, the reaction speed is doubled, which in turn means that the grid corrodes at twice the rate. Intensive gassing also considerably increases the danger of an explosion.
Sealed batteries, i.e. gel and AGM batteries, can become damaged by being overcharged just once. In these types of battery the electrolyte – the acid – is in a bonded form and cannot be topped up.
Discharge results in lead sulphate developing in the battery. If the battery is either not charged or not fully charged, then the lead sulphate will form crystals which grow and thus reduce the surface area of porous lead. These crystals are at best difficult, or at worst impossible, to convert back to lead sulphate. Depending on the state and the design of the battery, within a few days this can lead to a situation whereby the battery is no longer capable of receiving current, and therefore becomes unusable. But even if the battery is recharged immediately and appears to recover fully, there is generally some residual damage that will ultimately have a negative effect on the battery's service life. It is becoming increasingly common to find electronic components in vehicles that continue to consume current even after the engine is switched off. Examples of such "concealed" current consumers include alarm systems and radio clocks.
Storing batteries in a partially-charged state can contribute to premature ageing. This problem often occurs in occasional-use vehicles such as motorcycles, vintage cars or weekend boats, in which batteries stand for prolonged periods without being used. As soon as the charge status of the battery falls to below 50 per cent, the ageing process and sulphation of the battery speed up markedly.