Electric car chargers make our transportation tools more convenient to walk. As for the battery as a "convenient power source", it has always been widely used by people. Before 2003, ordinary people used it directly. As the popularity of electric vehicles in my country continues to increase, more and more batteries are closer to people’s lives. But people don’t know much about the battery: how to damage the battery too quickly, whether the battery with reduced capacity can be repaired, how to maintain the battery, etc., and so on. The discussion is as follows for readers' reference. Electric vehicle chargers share the reasons for damage to electric vehicle batteries.
Electric vehicles generally use maintenance-free lead-acid batteries, and the electrolyte is colloidal, divided into 24V, 36V, 48V and 60V. 36V and 48V are more on the market, and 24V and 60V are less. 24V is two cells, 36V is three cells, 48V is four cells, and 60V is five cells of 12V. The single cells are connected in series; each cell is 12V and consists of 6 series series, every 2V and every other positive Negative plate and colloidal electrolyte. The reasons for battery damage are very complicated, which can be roughly divided into the following 5 types:
1. "Overcharge" causes damage to the battery.
"Overcharge" is a phenomenon that causes damage to the chemical and physical properties of the battery caused by overcharging the battery.
"Overcharge" is the first reason for the charger. Current electric vehicle chargers have a safe charging voltage setting. The charging voltage is generally set within 1.2 times the battery standard voltage. For example, for a 48V battery, the charging voltage is set within 57.2V. During the process of discharging the battery, the voltage will gradually drop. When the battery is recharged, the red light of the charger will light up, indicating that when charging is in progress, when electric energy is continuously input to the battery, the voltage will continue to rise until it is close to or equal to The green light of the charger will light up when charging voltage, at this time, charging stops or trickle charging. If the charger voltage component fails, the charging will not stop, the charging current will be continuously input to the battery, the voltage will continue to rise, the result of the increase in voltage will aggravate the thermal reaction of the electrolyte, and the battery shell will be deformed ( Expansion), the heavy will cause the battery to be charged.
Secondly, the "overcharge" is caused by the imbalance of the voltage between the batteries. As mentioned above, the battery pack is composed of 2-5 12V batteries. When the batteries are just shipped from the factory, the voltage of each battery is very close to the battery, but after a period of use, the voltage between the batteries will be different, namely The so-called "differential pressure". The electric vehicle charger charges the battery packs connected in series at the same time when charging. The battery with higher voltage will be fully charged first, and the battery with lower voltage will be fully charged afterwards or even be charged all the time, because the charger is charged with the overall voltage Or stop charging, so the battery that is fully charged first will be in an "overcharged" state. When the "pressure difference" is small, the battery will not be affected much. When the "pressure difference" is large, the battery that is often "overcharged" will also produce an intensified thermal reaction of the electrolyte until the battery is charged.
2. "Loss of water" damages the battery.
"Water loss" is one of the basic reasons for the decrease in battery capacity. Most electric vehicles use maintenance-free lead-acid batteries. Many users will say that this kind of battery is sealed and maintenance-free. Why is there a phenomenon of "water loss"? The reason is very simple. Water is an important component that participates in the electrolysis reaction of the battery. Once the battery is overcharged, discharged with high current, increased internal resistance, short-circuited, etc., it is easy to generate heat and form water vapor. The water vapor is in the sealed battery box. Most of them will be retained, but a very small part will be lost (determined by the density of the battery shell material). Over time, the battery will appear "water loss". Generally speaking, an electric vehicle battery will have a "water loss" state after more than 6 months of use. The greater the motor power, the more serious the "water loss" state.
3. "Loss of electricity" causes damage to the battery.
"Power deficit" is a phenomenon that damages the battery plate coating caused by forced over-discharge when the battery power is insufficient and the voltage is low. You should know that there is a standard range for the working voltage of any on-board electrical appliance. Electrical appliances beyond this range are easily short-circuited or even burned. Under this range, electrical appliances cannot start or work normally, and even affect the service life. This is the case for on-board electrical appliances and batteries. Many users often charge every few days when using electric vehicles, and some of them travel more than 60% of the nominal mileage of the new battery every day. It is important to know that a decrease in battery capacity will lead to insufficient battery voltage (undervoltage), and insufficient voltage will not be effective. Meet the basic voltage supply of on-board electrical appliances. When the voltage drops, the user is still using the electric vehicle, and the battery cannot provide the normal voltage. Therefore, the battery will be under-voltage due to the load of the on-board electrical appliances. "Loss of electricity" will gradually peel off the lead layer of the battery plate until the plate is damaged.
4. The vulcanization of the electrode plate causes the battery to be damaged.
What is battery vulcanization? White hard lead sulfate crystals are formed on the plate, and it is very difficult to convert into lead sulfate, which is an active material, during charging. This is sulfation, or "sulfurization" for short. The reason for the formation of this lead sulfate is that lead sulfate particles dissolve in the electrolyte and become saturated when they are left for a long time after overdischarge or discharge. These lead sulfate recrystallize when the temperature is low, but precipitate in crystalline lead sulfate. In this way, the once-precipitated particles grow and develop again and again due to temperature fluctuations, and the crystal grains are enlarged. This kind of lead sulfate has poor conductivity, high resistance, low solubility and dissolution speed, and it is difficult to recover when charging. Therefore, it becomes the cause of reduced capacity and shortened life. Sulfuration is the main crux of the reduction in battery capacity, but the damage to the battery plates by high current is a greater crux of the reduction in battery capacity of electric vehicles.
5. The high current discharge caused by starting, accelerating and overloading damages the battery.
The instantaneous current when an electric vehicle starts and accelerates is very large, generally reaching 20A-50A. According to the power of the electric vehicle motor, the normal discharge current is generally controlled within 10A. Because the instantaneous current is too large, the electrolysis reaction will increase sharply, and the electrode plate coating will inevitably be affected to a certain extent. Over time, the electrode plate lead layer powder will gradually fall off due to the instantaneous high current pulling, and the electrolyte will turn black (lead powder To), the battery will be scrapped. Overload means that the load is overweight during the driving of the electric vehicle, such as excessive cargo and people. Overload will increase the discharge load of the battery. Long-term high-current discharge will directly affect the coating of the plate and accelerate the process of plate softening. In addition, bad road conditions will also make electric vehicles brake and start smoothly. Such as potholes, red lights, roadblocks, etc. These are all factors that cause high current discharge. It is also worth mentioning that the greater the power of the electric vehicle motor, the shorter the service life of the battery. This is because the greater the motor power, the greater the discharge current and the greater the damage to the battery.