Battery charging principle

The discharged battery must be charged before it can be put back into service;

The new battery and the repaired battery must be initially charged before first use;

In order to maintain a certain capacity and prolong the service life of the battery during normal use, it is necessary to carry out some necessary supplementary charging operations such as supplementary charging and balanced charging.

Therefore, the charging operation is an important part to ensure the good performance of the battery during the whole use process and prolong its service life.

According to the purpose of charging, the charging operation of the battery can be divided into initial charging, supplementary charging, desulfurization charging and the like.

Initial charging

The first charge of a new or repaired battery before use is called initial charging;

Purpose: To restore the amount of electricity lost by the partial active material on the plate during slow storage and self-discharge during storage.

Whether the initial charging is appropriate or not is extremely important for the performance of the battery.

The characteristics of initial charging: small charging current, long charging time, and sufficient electrochemical reaction.

2. Supplementary charging

When the battery is used on a vehicle, there is often a phenomenon of insufficient charging, especially for short-distance transportation vehicles, which should be recharged as needed.

Generally, once a month, if there are the following phenomena, you must recharge at any time:

1) The relative density of the electrolyte drops below 1.15;

2) The discharge in winter exceeds 25%, and the discharge in summer exceeds 50%;

3) The lighting is dim and the starter is running weak, indicating that the power is insufficient.

In addition, when the battery is left for more than one month, it should also be recharged; it should be recharged after a large amount of distilled water is added.

3. Cycle exercise charging

The battery is often partially discharged during use. The active substances participating in the chemical reaction are limited. In order to force the active material equivalent to the rated capacity to work, to avoid the active material shrinking for a long time without working, it can be performed every 3 months. Cycle exercise charging.

That is, after the battery is fully charged, the battery is discharged at a discharge rate of 20h, and then sent out after normal charging.

4. Desulfurization charging

When the plate is vulcanized more seriously, "desulfurization charging" can be performed.

5. Balanced charging

During the use of the battery, due to manufacturing, use and other factors, there will be differences in the terminal voltage, electrolyte density, capacity, etc. of each single cell. The method of equalization charging can eliminate this difference.

6. Charging method

To charge the battery, you must select the appropriate method according to the situation and use the charging device correctly. This will increase work efficiency and extend the life of batteries and charging equipment.

Generally, the charging method of the battery has two types of constant current charging and constant voltage charging. In recent years, rapid charging (pulse charging) has also been gradually promoted.

(1) Fixed current charging

During the charging process, the charging current is kept constant, called constant current charging, as shown.

The constant current charging has greater adaptability, and the charging current can be arbitrarily selected and adjusted, so that the battery can be charged in various situations. This method can be used for initial charging, supplementary charging, and desulfurization of new batteries. However, its disadvantage is that it takes a long time to charge and requires constant adjustment of the charging current.

(2) Constant pressure charging

During charging, the charging voltage U remains the same. The charging method is called constant voltage charging, as shown in the figure.

When using constant voltage charging, it is necessary to select the charging voltage: if the voltage is too high, not only the charging current is too large in the initial charging, but also the overcharging phenomenon may occur, causing the plate to bend and the active material to fall off a lot, and the temperature rise of the battery is too high; If the charging voltage is too low, the battery will not be charged.

Constant voltage charging also requires that the battery to be charged must be connected in parallel between the charging power sources. Since the battery is connected in parallel with the generator in the vehicle, the battery is always charged at a constant voltage of the generator (adjusted by the regulator).

The above charging methods are collectively referred to as "regular charging". It takes 60h to 70h to complete an initial charging, and about 20 hours to recharge. Due to the long charging time, it is very inconvenient to use.

(3) Pulse fast charging

Pulse fast charging can greatly overcome the polarization phenomenon generated during the charging process and effectively improve the charging efficiency.

Its charging current waveform is as shown:

The advantages of pulse fast charging are:

1 The charging time is greatly shortened. Generally, the initial charging is no more than 5h, and the supplementary charging is no more than 1h.

2 can increase the capacity of the battery. Rapid polarization can be eliminated due to pulse fast charging. Therefore, the chemical reaction during charging is sufficient, the depth of the reaction is deepened, and the capacity of the battery is increased. Therefore, the new battery can be used without discharging after initial charging, which not only saves energy but also brings convenience to use.

3 has a significant desulfurization effect. Since the pulse fast charging has the above advantages, the advantages are more prominent in the battery concentration, frequent charging or emergency use departments. However, the pulse charger control circuit is complicated, the price is higher than the ordinary charger, and it is not ideal in use, and needs further improvement.

(4) Identification of positive and negative polarity of battery during charging

When charging, connect the positive and negative poles of the battery to the positive and negative poles of the charger. Therefore, it is necessary to correctly determine the polarity of the battery.

The poles of the battery are generally marked with "ten" and "-" marks; or the positive column is painted red. If the label is ambiguous, it can be identified by the following methods:

1 Observe the color of the pole. The used battery positive column is dark brown and the negative column is light gray.

2 Connect the two poles of the battery with a DC voltage meter and judge the positive and negative poles according to the direction of the pointer yaw.

3 Use the electrolyte to identify, connect the two poles of the battery to the wire, insert them into the electrolyte separately (do not touch the two wires), and generate a large number of bubbles around the wire as the negative electrode.