How to choose a battery charger?

The importance of batteries for electric vehicles is self-evident. A lead-acid battery with stable quality and high quality should have the following main characteristics: 1. The initial capacity under nominal conditions should reach the nominal value to ensure the initial mileage of electric vehicles; 2. In the case of mass production, each battery (12V) has good consistency and meets the equilibrium conditions for series charging; 3. Statistical analysis is carried out after strict testing, and the charging technical requirements are accurate to ensure neither under-charging nor over-charging; 4. The early capacity decline is small; 5. The internal short circuit of the battery , open circuit, large internal resistance, valve out of control and other hard faults.

In fact, the continuation mileage, battery capacity decline and service life of electric vehicles in the initial and daily use are all related to charging, except for the battery itself. The battery is more often charged and damaged, which is a problem that many electric bicycle manufacturers and consumers are prone to neglect.

1. Correct charging mode

After the battery inputs a certain current, along with the chemical reaction, the positive and negative plates generate charge energy accumulation, and the battery terminal voltage increases accordingly. When the terminal voltage exceeds a certain value, severe hydrolysis, gas evolution and heat generation will occur inside the battery, resulting in water loss or even thermal runaway (the outer shell bulges). The design of the charger should be based on quantitative statistical analysis of the critical value of the terminal voltage. Some battery manufacturers, for commercial reasons, artificially modify or even deliberately increase the critical value, and chargers designed according to this will inevitably lead to overcharging. Although the short-term riding range of electric vehicles has increased, the life of the battery has been greatly shortened. On the contrary, the long-term undercharged state of the battery not only reduces the usable capacity, but also accelerates the passivation of the battery plate and exacerbates the early capacity decline.

It can be seen that the charger design must pass a large sample test of the battery to verify the charging technical conditions of the battery manufacturer, and then establish a reasonable charging mode, so that the battery in service is neither overcharged nor undercharged to prevent excessive water loss. Reduce sulfation and extend battery life.

According to the current situation of lead-acid batteries, the multi-stage charging mode of constant current----limited current and constant voltage----trickle current supplement is an ideal choice, which has been widely recognized by the battery industry. If a certain maintenance and repair function is added while accurately controlling the threshold value, it will play a very important role in ensuring the discharge capacity of the battery and prolonging the service life.

2. Exact parameter control

As mentioned above, in the multi-stage charging mode, the values ​​of current and voltage must be accurately set, and comprehensive compensation should be made with the change of ambient temperature, so that the battery can be overcharged or undercharged in four seasons. The factors that affect the control accuracy are as follows: 1. Reasonable circuit design; selection of components, rejecting fake and shoddy products; 3. Strict testing, each aging, and re-inspection before leaving the factory. The view that the charger can be charged is completely wrong.

3. Quality and long-term reliability

Although the charger is small and the value is relatively low, compared with general electronic products, the quality requirements are very high. First, it is often charged and used frequently; second, the continuous working time is long, the charging current is large, and the safety requirements are high; third, it has obvious heat generation; fourth, some users use harsh environment, environmental temperature, humidity Changes are big, and at the same time, because it is often carried in the car, the anti-vibration design is essential. To ensure product quality, the selection of components and the process flow are very important. From circuit boards, power chips, to resistors and shock-absorbing pads, authentic and high-quality products must be selected. If you blindly emphasize cost and selling price, you will inevitably cut corners, cause hidden dangers in quality, bring product failures and service disputes, and affect the brand and reputation of electric vehicles.