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All colleagues unite and focus their efforts to write a new chapter of developmentCharging methods of four types of electric vehicle chargers
所属分类： Industry News
发布时间：2020-07-13
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Electric vehicle charger Are you familiar with the common methods? Here’s a detailed guide to four ways to charge an electric vehicle!
1. Electric vehicle charger—Float charging
For batteries that are used intermittently or only during AC power outages, the charging method is float charging. For example, in stationary applications, a voltage of 2.15 to 2.2 V is applied across each individual cell, with continuous charging conducted at a very small current. The charger is connected in parallel with the battery; the charging current primarily compensates for self‑discharge losses, typically ranging from about 0.3% to 1.0% per 10-hour rate. Under normal operating conditions, the charger supplies the load, and during short periods of high demand, the battery provides the necessary power. In such cases, the battery automatically resumes charging as its terminal voltage drops.
2. Electric vehicle charger—Equalization charging
For battery packs composed of numerous individual cells, such as stationary lead‑acid batteries, periodic equalization charging is required after a certain period of operation. This is because, during routine charging under identical conditions, the active materials on different parts of the plates experience varying degrees of charge, leading to an imbalance in the electrochemical reactions. Furthermore, given that individual cells may exhibit differences in their charge–discharge characteristics, some cells can become undercharged. Therefore, after normal charging is completed, the battery should be recharged for 1 to 3 hours at a current corresponding to approximately the 20‑hour rate. This type of charging is also referred to as overcharging. In general, when batteries are operated under consistent conditions, performing regular equalization charging as part of routine maintenance is beneficial.
The interval between equalization charges varies according to each user’s specific requirements; some stipulate that it be performed once every three or six months. In recent years, with advances in battery design and manufacturing technologies, the performance differences among batteries have become relatively minor, leading to a trend toward longer intervals for equalization charging.
3. Electric vehicle charger — constant-voltage, current-limited charging
Constant‑voltage current‑limiting charging is primarily used to address the drawback of excessive charging current in constant‑voltage charging (the same method as constant‑voltage charging) by inserting a series resistor—known as the current‑limiting resistor—between the charging power supply and the battery being charged, thereby automatically regulating the charging current.
When the charging current is too high, the voltage drop across the current‑limiting resistor becomes significant, thereby reducing the charging voltage; conversely, when the charging current is low, the voltage drop across the resistor is minimal, and the voltage loss at the charger’s output is also small. In this way, the charging current is automatically regulated to remain within a specified limit. This method is currently widely used for the initial charging of maintenance‑free batteries and for topping up ordinary batteries.
4. Electric vehicle charger — constant-voltage charging
Constant‑voltage charging involves charging each individual cell at a fixed voltage—typically the number of cells in the battery pack multiplied by 2.5 V. Its main characteristics are as follows: at the beginning of charging, the current is relatively high, and both the battery’s electromotive force and the electrolyte’s specific gravity rise rapidly; as charging progresses, the current gradually declines, leaving only a very small current near the end of the cycle. This method features short charging times and low energy consumption; after about 4–5 hours, the battery can typically reach 90%–95% of its rated capacity. With an appropriately selected charging voltage, the entire process can be completed in as little as 8 hours, and it requires no continuous supervision, making it widely used for topping up batteries.
The drawbacks of constant‑voltage charging are as follows: due to the excessively high initial charging current, when charging a deeply discharged battery, the initial current can rise sharply, easily leading to overcurrent in the battery and damage to the charging equipment; during the charging process, because the charging current cannot be adjusted, this method is unsuitable for initial charging or desulfation charging; furthermore, since voltage variations during charging are difficult to compensate, it is challenging to achieve full charge for batteries whose capacity recovers slowly.