Charger classification and operation


Charger classification: distinguished by transformers w […]

Charger classification: distinguished by transformers with and without power frequency (50 Hz), can be divided into two categories. Freight three-wheel chargers generally use chargers with power frequency transformers, which are large, heavy, and expensive, but reliable and cheap; electric bicycles and electric motorcycles use so-called switching power supply chargers, which save power and have high efficiency, but Perishable. Commonly used switching power supply chargers are divided into half-bridge and single-excitation types, and single-excitation types are divided into forward and flyback types. The half-bridge type has high cost and good performance, and is often used in chargers with negative pulses; the single-excitation type has low cost and high market share.
Lead-acid batteries have a history of more than 100 years, and they have started to follow the old viewpoints and operating procedures: the charge and discharge rate is 0.1C (C is the battery capacity) and the life is longer. In order to solve the problem of fast charging, American Mr. Max released his research results to the world in 1967, charging with a pulse current greater than 1C, and discharging the battery during intermittent charging. Discharge helps to eliminate polarization, reduce the temperature of the electrolyte, and improve the ability of the plates to accept charge.
Some science and technology workers in China made various brands of fast chargers according to Mr. Max ’s three laws around 1969. The charging cycle process is: high-current pulse charging → cutting off the charging path → briefly discharging the battery → stopping the discharge → connecting the charging path → high-current pulse charging ... Around 2000, some people applied this principle to electric vehicle chargers. During the charging process, the charging path is not cut off, and the battery is short-circuited with a small resistance to discharge. Since the charging path is not cut off during short circuit, an inductance is connected in series in the charging path. Generally, the short circuit is 3 to 5 milliseconds (1 second = 1000 milliseconds) within 1 second. Because 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 positive and the discharge is naturally negative, the term "negative pulse charger" appears in the electric vehicle industry, and it can be said to extend battery life and so on.
In recent years, electric vehicles have generally used so-called three-stage chargers. The first stage is called the constant current stage, the second stage is called the constant voltage stage, and the third stage is called the trickle stage. For the battery from the perspective of electronic technology: the first stage is called the charging current limiting stage, the second stage is called the high constant voltage stage, and the third stage is called the low constant voltage stage. During the conversion between the second and third stages, the panel indicators change accordingly. Most chargers have red lights in the first and second stages, and green lights in the third stage. The conversion between the second stage and the third stage is determined by the charging current. If it is greater than a certain current, it will enter the first and second stages, and if it is less than a certain current, it will enter the third stage. This current is called the switching current, also called the turning current.
When buying a new charger, check the three important parameters of the three-stage charger. The first important parameter is the low constant voltage value in the trickle stage, the second important parameter is the high constant voltage value in the second stage, and the third The important parameter is the conversion current. These three important parameters are related to the number of batteries, the capacity Ah of the battery, the temperature, and the type of battery. Users can generally measure the low constant pressure value of the third stage. The method is to connect the battery to the charger without connecting the battery, and measure the output voltage of the charger with the 200V DC voltage of the digital multimeter. The other two parameters, high constant voltage value and turning current, generally require special tools to measure.
The correct operation of the switching power supply charger is: when charging, insert the battery first, and then add the commercial power; when it is sufficient, cut off the commercial power first, and then pull out the battery plug. If the battery plug is pulled out during charging, especially when the charging current is large (red light), it is very easy to damage the charger.
In addition, it should be noted that: 1, after the green light, then charge for 2-3 hours. 2. The principle is shallow discharge (electricity) and frequent charging (electricity), that is, if the ride is not far enough, it should be charged in time to avoid recharging. 3. If you don't ride for a long time, you should charge it regularly (2-3 months). 4. For a long-term shallow discharge battery, a deep discharge is performed in about 3 months, which is the so-called light recharge, which is beneficial to the activation of long-term immobile substances in the deep part of the battery. The meaning of lighting is to ride until the controller battery undervoltage protection action. 5. After the new battery is put into use for 8-10 months, the battery should be inspected and maintained. 6. Generally, the chargers matching with famous brand cars are screened and usually do not need to be tested, but the non-supporting chargers purchased separately from the market must be tested for the aforementioned three parameters. 7. There is a thyristor charger without a power frequency transformer that directly rectifies the mains electricity to charge the battery. The current can reach 30A and the voltage is adjustable from 12V to 80V. Do not touch the battery before the mains electricity is completely cut off. Customers who use this type of charger for three rounds should pay special attention to safety.

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