Classification of chargers
Distinguished by the presence or absence of an I.F. (50 Hz) transformer, they can be divided into two main categories. Freight tricycle chargers generally use the charger with industrial frequency transformer, large size, weight, power consumption, but reliable and cheap; electric bicycle and electric motorcycle use the so-called switching power charger, power saving, high efficiency, but easy to break.
The correct operation of the switching power charger is: when charging, insert the battery first, then add the mains; after sufficient, first cut off the mains, then pull the battery plug. If you unplug the battery 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 half-bridge and single-excited type two categories, single-excited class is divided into forward and flyback type two categories. The half-bridge type has high cost and good performance, and is often used in chargers with negative pulse; the single-excited type has low cost and high market share.
About negative pulse chargers
Lead-acid batteries have been more than 100 years of history, the beginning of the world generally along the old views and operating procedures: charge and discharge rate of 0.1C (C is the battery capacity) longer life. American Mr. Max to solve the problem of rapid charging, in 1967 to the world announced his research results, with greater than 1C rate pulse current charging, charging interval to discharge the battery. Discharging is good for eliminating polarization, reducing electrolyte temperature and improving the ability of the electrode plate to receive charge.
Some scientific and technical workers in China made a variety of brands of fast chargers successfully around 1969 according to Mr. Maes' three laws. The charging cycle process is: high current pulse charging → cut off the charging path → briefly discharge the battery → stop discharging → turn on the charging path → high current pulse charging ......
Around 2000, someone used this principle in the electric car charger, charging process, not cut off the charging path, with a small resistor to short-circuit the battery momentarily, to discharge. The short circuit is connected in series with an inductor in the charging path because the charging path is not cut off. Generally in 1 second short circuit 3-5 milliseconds (1 second = 1000 milliseconds), because the current in the inductor can not jump, short circuit time is short, can protect the power conversion part of the charger. If the charging current direction is called positive, the discharge is naturally negative, the electric vehicle industry has emerged the term "negative pulse charger", and said that it can extend the battery life and so on.
About the three-stage charger
In recent years, electric vehicles commonly use the so-called three-stage charger, the first stage is called constant current stage, the second stage is called constant voltage stage, and the third stage is called trickle stage. From the electronic technology point of view for the battery: 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 is more appropriate. The second stage and the third stage of conversion, the panel indicator changes accordingly, most chargers are red lights in the first and second stage, the third stage becomes green. The second stage and the third stage of the interconversion is determined by the charging current, greater than a certain current into the first two stages, less than a certain current into the third stage. This current is called the conversion current, also known as the turning current.
Early chargers, including brand-name car chargers, although also change the light, but the actual constant-voltage current-limited charger, and not a three-stage charger. Generally such on a stable voltage value, 44.2V or so, for the then high specific gravity sulfuric acid of the battery is still put together.
About the three key parameters of the three-stage charger
The first important parameter is the low constant voltage value of the trickle stage, the second important parameter is the high constant voltage value of the second stage, and the third important parameter is the conversion current. These three important parameters are related to the number of batteries, related to the capacity Ah of the batteries, related to the temperature and related to the type of batteries. To make it easier to remember, the following is a brief example of a three-stage charger used in the most common electric bicycle (three 12V series-connected 10Ah batteries).
First discuss the low constant voltage value in the trickle stage with a reference voltage of about 42.5V. This value is high will make the battery water loss, easy to make the battery heat deformation; this value is low is not conducive to battery sufficient power. This value should be lower than 41.5V in the south; colloidal batteries should be lower than 41.5V, such as in the south also a little lower. This parameter is relatively strict and can not be greater than the reference value.
Next, discuss the second stage of the high constant voltage value, the reference voltage of 44.5V or so. This value is high conducive to rapid charging, but easy to make the battery water loss, charging the late current down, the result of the battery heat deformation; this value is low is not conducive to rapid battery charging, conducive to the trickle phase conversion. This value is not as strict as the first value, but do not be too high.
Finally, discuss the conversion current, the reference current is about 300 milliamps. This value is high for battery life, not easy to heat deformation, but not conducive to rapid battery charging; this value is low (external line) is conducive to sufficient power, but due to a longer period of high voltage charging, easy to make the battery water loss, so that the battery heat deformation. Especially when individual battery problems, the charging current does not drop below the turning current, it will even involve the good battery is also charged bad. The given reference value has a certain range, plus or minus 50 milliampere or even 100 milliampere are allowed, but not less than 200 milliampere.
At present, there are many high constant voltage value of 46.5V, low constant voltage value of 41.5V, turn current greater than 500 milliampere flyback cheap chargers on the market.
In the case of a charger for four 12V batteries, i.e. a 48V charger, the first two parameters are the aforementioned voltage reference value divided by three times four. The high constant voltage value is about 59.5V and the low constant voltage value is about 56.5V.
If the battery is larger than 10Ah, the third parameter current value will be increased appropriately, for example, 17Ah battery can be as large as 500 mAh.
Buy a new charger to check the three important parameters of the three-stage charger, the user can generally measure the third stage of the low constant voltage value themselves. The method is, without connecting the battery, add mains power to the charger and measure the output voltage of the charger with the 200V DC voltage file of a digital multimeter. The other two parameters high constant voltage value and turn current generally require special tools to measure.
Then add some correct charging methods: 1, after the green light and then charge 2-3 hours. 2, the principle of shallow discharge (electricity) diligent charging (electricity), is not far enough to ride, but also to charge in time to avoid recharging. 3, long-term non-riding, to regularly (2-3 months) charge once. 4, long-term shallow discharge of the battery, about 3 months The battery should be deep discharged once, which is called discharge and then recharge, which is conducive to the activation of the long-term immobile material in the deep part of the battery. The meaning of discharge is to ride until the controller battery undervoltage protection action.
Need to remind customers of several points
1, the general new battery into use after 8-10 months, to check and maintain the battery.
2, the general brand-name car supporting the charger is screened, usually without testing, but alone to the market procurement of non-supporting charger, be sure to carry out the aforementioned three parameters of the test.
3, there is a controlled silicon charger without frequency transformer, direct rectification of utility power for battery charging, the current can be 30A, voltage 12V-80V adjustable, do not completely cut off the utility power before, do not touch the battery, freight tricycle customers who use this type of charger should pay special attention to safety.
