Operation and charging of lead-acid batteries

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 the negative electrode sulfuric acid electrolyte. The electrodes and the entire battery are made in such a way as to increase surface area where 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, and in its place 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. Contrary to 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. Incidentally, the quantity the energy needed to charge the battery is slightly higher than that which we gain from it, mainly due to thermal losses on the internal resistance of the battery during the current flow 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. However, before we describe what these phenomena are, we want to emphasize that there is a simple way to prevent both sulphation and overcharging - just use a timer, a dedicated charger / charger and get into the habit of regular charging. Therefore it's necessary to know your lead acid battery should be fully charge, never allow it to be completely discharged and always charge it 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 simple and natural-to-use timers, which we wrote about in other posts on this blog (e.g. Ansmann AES1 switch). These types of timers 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 us, Ansmann AES1 circuit breaker can be purchased from us: Link

Sulphation:

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 quantity work we can get from him). 

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 then be especially careful when disassembling, replacing and disposing of it, because the accumulated gases may 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 gloves protection on face)

Finally, we will add that there are different technologies for building lead acid batteries that they reduce the effects of sulfation, reloading and other unfavorable phenomena depending on the application. Batteries sold by GO ELECTRIC with Błyskawica mopeds are among the best and the safest technologies, and the included chargers are dedicated to them. 

[The source of the illustration and the above description is, inter alia, 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–acid_battery

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