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Basic principles and classification of EV charger


Basic principles and classification of EV charger

The  EV charger is a charging device specially configured for the battery of the electric bicycle! 

Classification of  EV charger:

It can be divided into two categories with and without power frequency (50 Hz) transformers. Cargo three-wheel chargers generally use chargers with power frequency transformers, which are large in size, heavy in weight, and consume electricity, but they are reliable and cheap; electric bicycles and electric motorcycles use so-called switching power supply chargers, which save electricity and have high efficiency, but fragile.

The correct operation of the switching power supply charger is: when charging, insert the battery first, then add the mains power; If you pull out the battery plug first when charging, especially when the charging current is high (red light), it is very easy to damage the charger.
Commonly used switching power supply chargers are divided into two types: half-bridge type and single-excitation type, and single-excitation type is divided into two types: forward type and flyback type. The half-bridge type has high cost and good performance, and is often used in chargers with negative pulses; the single-excited type has low cost and high market share.
Negative pulse charger
Lead-acid batteries have a history of more than 100 years. At the beginning, the old viewpoints and operating procedures were generally adopted all over the world: the charging and discharging rate is 0.1C (C is the battery capacity) and the service life is longer. In order to solve the problem of fast charging, Mr. Max, an American, announced his research results to the world in 1967, charging with a pulse current greater than 1C rate, and discharging the battery when charging is intermittent. Discharge is beneficial to eliminate polarization, reduce the temperature of the electrolyte, and improve the ability of the plates to accept charges.
Around 1969, some scientific and technological workers in our country successfully produced various brands of fast chargers according to Mr. Max's three laws. The charging cycle process is: high current pulse charging→cut off the charging path→discharge the battery briefly→stop discharging→connect the charging path→high current pulse charging...
Around 2000, someone applied this principle to the electric vehicle charger. During the charging process, the charging path was not cut off, and the battery was short-circuited with a small resistor for an instant to discharge. Since the charging path is not cut off during short circuit, an inductor is connected in series in the charging path. Generally, the short circuit is 3-5 milliseconds within 1 second (1 second = 1000 milliseconds). Since the current in the inductor cannot jump, the short circuit time is short, which can protect the power conversion part of the charger. If the direction of the charging current is called positive, the discharge will naturally be negative, and the term "negative pulse charger" has appeared in the electric vehicle industry, and it is said that it can prolong the battery life and so on.

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