A storage battery is a device that directly converts chemical energy into electrical energy. It is designed to be rechargeable, achieving recharging through a reversible chemical reaction. It typically refers to lead-acid batteries, a type of secondary battery. Its working principle is as follows: during charging, external electrical energy regenerates the internal active materials, storing electrical energy as chemical energy. When discharging is needed, the chemical energy is converted back into electrical energy for output, such as in commonly used mobile phone batteries.
The common charging methods for storage batteries are as follows:
(1) Constant current charging
The charging process uses a constant current. This charging method is suitable for battery packs consisting of multiple cells connected in series, and the capacity of lagging cells can be easily recovered. The disadvantages are that the initial charging current is too low, while the charging current becomes too high in the later stages, resulting in a long charging time, excessive gas evolution, significant impact on the plates, high energy consumption, and low charging efficiency. It is rarely used nowadays.
(2) Constant voltage charging
During charging, a constant voltage is maintained. The initial charging current is quite high, gradually decreasing as charging progresses, and finally dropping to only a small current towards the end of charging.
A very small current flows through the battery. This method is relatively simple, produces a small amount of gas during charging, has a short charging time, low energy consumption, and high charging efficiency. The disadvantages are that if the charging current is too high in the initial stages of charging, the battery may be damaged due to overcurrent; if the charging voltage is too low, the charging time will be too long; and it is difficult to fully charge lagging batteries.
(3) Constant voltage current limiting charging
A resistor connected in series between the charging power supply and the battery is called a current-limiting resistor. When the current is large, the voltage drop across it is also large, thus reducing the charging voltage; when the current is small, the voltage drop across the resistor is also small, resulting in less output voltage loss from the charging device. This method overcomes the shortcomings of constant voltage charging and can automatically adjust the charging current to ensure it does not exceed a certain limit, thus limiting the current in the initial stage of charging.
(4) Fast charging
This method involves supplying current to the battery in pulses, and as the charging time continues, the battery experiences a momentary large current discharge (called a negative pulse) that depolarizes the electrodes.
Fast charging requires dedicated charging equipment to provide pulse current and negative pulses to ensure that neither a large amount of gas is generated nor heat is generated during charging, thereby shortening the charging time.
(5) Equalization charging
For a group of batteries operating under float charging, even though all the batteries in the group are under the same conditions during long-term operation, due to some reason,
Each battery has a different self-discharge rate, resulting in some batteries being undercharged and causing an imbalance in the entire battery pack. In this situation, to compensate for the voltage imbalance that occurs during battery use and restore it to the specified range, equalization charging should be used to eliminate the differences between batteries and achieve overall pack balance.
