The above diagrams show the operation of a typical battery used in electric (and internal combustion) vehicles using a lead-acid battery as an example. Since Volta, who invented the battery in 1800, most batteries and accumulators, including those used in vehicles, are built on a similar principle - they have one or more interconnected cells, each consisting of two metal electrodes made of different materials separated by electrolyte. In the case of a lead-acid battery, lead dioxide forms the positive electrode, lead dioxide forms the negative electrode, and sulfuric acid forms the electrolyte. The electrodes and the battery as a whole are made so as to increase the surface area where the two main chemical reactions can take place whereby the battery generates electricity in a closed circuit as shown in diagram 4.20b. As we can see from this schematic picture and chemical reaction formulas, as electricity flows through the circuit (in the form of electrons) in the battery, the electrolyte is lost, in the place of which water and PbSO4 are formed. This results in a decrease in the electromotive force of the cells and a decrease in the potential difference at the battery terminals. Unlike batteries, however, in batteries this process can be reversed thanks to the appropriate selection of materials, electrodes and electrolyte. This happens when we connect an appropriate charger or rectifier, which, thanks to a higher voltage than that at the battery terminals, will force the current to run in the opposite direction, which in our illustrative battery will literally cause the opposite course of the described chemical reactions, because PbSO4 will be decomposed back into lead and dioxide lead. By the way, the amount of energy needed to charge the battery is slightly higher than the amount we gain from it, mainly due to thermal losses on the internal resistance of the battery as current flows through it.

Practical aspects:

Writing theoretically about lead-acid batteries, we would also like to draw your attention to several important practical aspects related to their charging, in particular their sulphation and overcharging. Before we describe what these phenomena are, however, we want to emphasize that there is a simple way to prevent both sulfation and overloading - all you need to do is use a timer, a dedicated charger / charger and get into the habit of regular charging. Therefore, it is necessary to know that a lead-acid battery should be fully charged, never fully discharged and always charged after use, and when it is standing unused, disconnect it from the vehicle's circuit and charge it periodically (e.g. with a timer). In everyday use, such a habit develops automatically when you use the simple and natural time switches we wrote about. in other entries on this blog (e.g. Ansmann AES1 switch). These types of timer switches not only protect the battery from discharging and overcharging, but also facilitate its daily charging in electric vehicles - just connect the charger cable to the vehicle and press the button on the timer. Recommended by Ansmann AES1 circuit breaker can be purchased from us: Link

Sulphate:

A very important practical aspect of charging lead-acid batteries is the unfavorable phenomenon of their unintentional sulfation. Well, if a battery of this type is not charged sufficiently or is completely discharged without being charged immediately, sulfate crystals are formed in large quantities, which are deposited on the electrodes and reduce the amount of available PbSO4 for the electrochemical reactions described above. The irreversible effects of these processes include increase in internal resistance, extended charging time and significantly reduced battery discharge current (and thus the amount of work we can get from it).

Reloading:

The second, less frequent, but also important problem that can arise when using lead-acid batteries is their overcharging, when they are charged either with too high current or for a very long time. Too much free hydrogen and oxygen are then produced, which either escape from the battery or remain outside the chemical cycle, increasing the internal pressure in the battery. This can increase the acidity and corrosivity of the electrolyte and may be manifested by increased voltage at the battery terminals. Although lead-acid batteries are safer than lithium batteries, in extreme overcharging situations, a lead-acid battery may swell from excessive internal pressure, which should be especially careful when disassembling, replacing and disposing of it, because the accumulated gases can cause fire and explosion, during which battery fragments and sulfuric acid are scattered around. (therefore it is recommended to use protective clothing, gloves and full face protection)

Finally, we add that there are various technologies for the construction of lead-acid batteries that reduce the effects of sulfation, overcharging and other adverse effects depending on the application. Batteries sold by GO ELECTRIC with Błyskawica mopeds are among the best and safest technologies, and the attached chargers are dedicated to them.

[The source of the illustrations and the above description include the following items where interested people can find more information:

1) "Electricity and magnetism" by EDWARD M. PURCELL and DAVID J. MORIN (third edition), chapter 4.9 "Electromotive force and the voltaic cell";

2) https://en.wikipedia.org/wiki/Lead%E2%80%93acid_battery

3) https://www.mpoweruk.com/chargers.htm]