Technical requirements and characteristics of primary charging of lead-acid batteries
2022 May 14 By admin 0 comment

The initial charging method is suitable for new batteries, or batteries that have been overhauled or dry-stored after replacing the plates.
The so-called initial charging is the process of charging for a long time with a small current. How the new battery is initially charged not only directly affects its capacity and life, but also affects the performance of the battery in the future. This shows that the initial charging of the battery is a crucial technology, which is different from the usual charging technology. The following introduces the initial charging technology of the new battery by the constant voltage charging method and the staged charging method.

  1. Characteristics and requirements of initial charging

The new battery can only be initially charged after injecting a suitable amount of qualified standard density electrolyte at a certain ambient temperature. Usually, a dilute sulfuric acid solution with a density of 1.21g/cm³ is injected at 20°C, and the liquid level should be 10mm~15mm higher than the electrode plate. After the new battery is injected with the electrolyte, it will immediately react chemically with the plates to increase the temperature. Therefore, it should be allowed to stand for a few hours after injection, and the battery can be charged only when the temperature of the electrolyte drops below 35°C. Before charging, the lid of the filling hole should be opened, so that the hydrogen and oxygen gas generated during charging can be discharged in time to avoid the expansion and damage of the battery.

Battery charging requires a charger (generator) or a charger (DC power supply). When selecting a charging device, consider its capacity, that is, whether it can provide a certain voltage and a large enough current. The charging should be connected to the circuit, and the polarity of the charger and the battery must not be reversed. The output voltage of the charger should be higher than the rated voltage of the battery, and the charging voltage distributed by the charger to the single battery needs to be 2.5v, and the size of the charging current should be able to be adjusted.

The initial charging of various batteries should be carried out according to the indicators specified in the manufacturer’s instructions (if you want to know more indicators and precautions for battery charging, please visit Tycorun Battery), first pour the electrolyte of the specified density, and adjust the specified The initial charging current value, and then charging according to the specified charging time. If there is no original data reference specified by the manufacturer, it should be ensured that the density of the electrolyte should not exceed 1.22g/cm³. The initial charging current can be calculated as follows:

In the formula: 1 is the initial charging current (A); K is the ratio of the initial charging current, generally taking 4.2-4.7; C is the rated capacity of the battery to be charged (A h); t is the initial charging time (h) ).

According to practical experience, the initial charging current of the battery can use a current not greater than C10 as the initial charging current. Based on the technical data of various manufacturers, the current of C15 is suitable; because the initial charging current of the battery is small, the charging time must be longer. Generally, 70h-90h; the initial charge should be 4.2 to 4.7 times the rated capacity of the battery. And in the process of initial charging of the battery, the charging current and voltage should be recorded every hour as the basis for calculating the charging capacity.

  1. Initial staged charging technology

The initial charge of a new battery can be done in a phased approach. The following will introduce the method and steps of the initial charging of the new lead-acid battery for motorcycles.
(1) Add a certain density of electrolyte to the battery according to the manufacturer’s regulations. At this time, the electrolyte will penetrate into the electrode plate and the separator, and the chemical reaction and heat generation will occur immediately.

(2) The lead-acid battery is placed for 4h-6h after adding liquid, so that the heat generated by the chemical reaction can be dissipated, and the charging can be started when the temperature of the electrolyte is lower than 35℃. In addition, since the electrode plate and the separator absorb part of the electrolyte to lower the liquid level, the electrolyte should be added to the specified height before charging.

(3) In the first stage, the current of C14 is used to charge, and it is charged until the voltage of the single cell rises to 2.4v and the electrolyte starts to bubble.

(4) The second stage is charged with C/28 current until a large number of bubbles emerge from the electrolyte, and the voltage of the single cell can be stabilized at 2.5v, and the voltage will not continue to rise within 2h-3h, indicating that The battery is fully charged and can stop charging.

(5) After the battery is charged for the first time, the density of the electrolyte should be adjusted. If the density is too small, adjust with dilute sulfuric acid with a density of 1.4g/cm³; if the density is too large, adjust with distilled water, and make the liquid level meet the requirements.

Then continue to charge with C/28 current for half an hour to mix the electrolyte evenly, and make a review. If the density is still not suitable, it still needs to be adjusted until the density remains unchanged and meets the specified value. Finally, wipe the battery case clean and you can deliver it for use. Table 1 lists the technical parameters of the initial staged charging of several motorcycle start-up lead-acid batteries.

Table 1 - The technical parameters of the initial staged charging of the lead-acid batteries used for starting several motorcycles
Table 1 – The technical parameters of the initial staged charging of the lead-acid batteries used for starting several motorcycles
  1. Judgment criteria for completion of initial charging

Whether the initial charging is completed, in addition to referring to the charging time, should also be comprehensively judged according to the following actual conditions.
(1) Strong bubbles have emerged from each single battery, which means that it has been fully charged.
(2) The density of the electrolyte has risen to 1.21g/cm³ at the time of injection, and does not continue to rise within 3h, indicating that it has sufficient electricity.
(3) The voltage of each single battery has risen to 2.5V, and it has not continued to rise for 3h, which also means that there is sufficient electricity.

During the initial charging process, the charging current should not be interrupted. If the charging temperature of the battery has a tendency to rise to 40°C, it should be cooled in advance by means of fan cooling, cooling with cold water outside the shell, or appropriately reducing the charging current. If the cooling effect is not large, the charging can be suspended for 3h-4h, but the charging time should be extended at the end so as not to reduce the total amount of electricity that needs to be charged for the initial charging. After the battery is fully charged, screw on the liquid hole plug in time, and at the same time keep the vent hole on the liquid hole plug clean and unobstructed.

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