Introduction to the use of lithium batteries

All lithium batteries, whether they are in the past or in recent years, including: polymer lithium batteries, lithium iron phosphate batteries, etc., are very afraid of internal short circuits, external short circuits, and overcharging. Because the chemical nature of lithium is very active and it is easy to burn. When the battery is discharged and charged, the inside of the battery will continue to heat up, the gas that appears during the activation process will expand, the internal pressure of the battery will increase, and the pressure will reach a certain level. , It will break, causing leakage, fire, or even explosion. In order to alleviate the danger of lithium batteries, technicians have added ingredients that can inhibit the activity of lithium (such as cobalt, manganese, iron, etc.), but these do not essentially change the danger of lithium batteries. So be very careful when using it! 1) Charging: The safe working voltage range of lithium battery is 2.8~4.2V, lower or higher than this voltage range, the lithium ions in the battery become very unstable, and even cause accidents. In order to ensure that the battery is in a safe range, a special charger is required. These chargers will automatically adjust the charging method according to the current state of the battery. Three stages are commonly used in lithium batteries. ①Activation: Before the charger starts charging, it will supply the battery with a small current, and test the battery voltage change at the same time, and gradually increase the current until the set value. This process can be regarded as a kind of activation or detection charging. ②Constant current and variable voltage charging: The charger charges the battery with a constant current. As the battery voltage increases, the charger increases the charging voltage at the same time to speed up the charging speed. ③Variable current and constant voltage charging: When the battery reaches the 4.2V cut-off voltage, the battery will only charge about 70% of the power (not full). At this time, the charger continues to charge the battery with a constant voltage and a gradually decreasing current. When the value is less than 0.1A, the battery is still charged and the battery voltage continues to rise before stopping the charging. This way the battery is overflowing. The charging current proposal in the general industry is 2C charging, that is, 2 spares of battery capacity. For example, your battery is 2200mAh, 2C charging is 2200mAHX2Cu003d4400mAh, and the charger is adjusted to 4.4A. To charge a 350mAh battery, that is, 350mAhX2Cu003d700mAh, the charger adjusts the charging current to 0.7A. And so on. Of course, many batteries currently support high-current charging, and all support up to 5C. Let’s talk about balance. This is an intelligent operation that is unique to the use of series charging for batteries above 1S. In order to obtain a higher voltage output, we use multiple batteries in series, so when charging, there are two ways: ① series charging: for example, 3S (11.1V), the charger is connected in series with 11.1V voltage at the same time The 3 batteries are charged. (For example: IMAXB6) ② Parallel charge: For example, 3S (11.1V), the charger separately charges each cell with 4.2V voltage. (For example: UNAA6) Obviously, the parallel charging method is independently controlled by each cell. It is the same as charging a single 1S battery. However, serial charging may encounter a situation. For example, one of the three batteries has reached the 4.2V cut-off voltage, while the other two have not reached the cut-off voltage. What should I do? At this time, the voltage balance of the 3 cells is required. A typical B6 is this way, it will discharge the high-voltage battery, and then charge the whole group, and finally reach a balance and fullness. Knowing this charging process, you can understand the difference between a charger of about 10 yuan and a charger of hundreds of yuan. Inexpensive chargers only rely on a few switching tubes to achieve cut-off voltage control, which is either dissatisfied or overcharged. A good charger uses a single-chip microcomputer to test the battery status synchronously to control the switching of the charging mode. 2) Discharge: Pay attention to over-discharge during discharging. The safety voltage of lithium battery is 2.8~4.2V. If the voltage is lower than 2.8V, the lithium ion will enter the attenuation state. Once attenuated, it will not be activated and cannot be charged. But our old model friends say not to be lower than 3.6, there may be misunderstandings! We have to distinguish two voltages: ①: load voltage: when the battery is under load, such as when an airplane is flying ②: no-load voltage: when there is no power output. For example, during a flight, the battery voltage may be at 3.3V, but after a few minutes after being unplugged, the voltage will rise to about 3.6. In the past, there was no two-way transmission in the old model friends, so you can’t see the battery voltage in flight. It is basically measured after getting off the plane, so don’t be lower than 3.6V and have been passed down. To be correct, the load voltage should not be low It is more reasonable at 3.2V. Occasionally over-discharging once and a half is actually not so terrible. As long as the load is not less than 2.8, it is basically safe (depending on the battery quality, batteries lower than 3.2V are easy to over-discharge. There are some batteries, A few tenths of a second, so I suggest not to try it lightly) 3) Storage: A lot of new chickens, throw things into the box after playing the plane. Or some model friends are accustomed to recharging their batteries, and they can fly anytime when they want to fly! , These two habits are very undesirable. The best storage voltage of lithium battery is 3.7~3.8V. Lithium ions are in the most stable state in this state. Any battery has the characteristic of self-discharge (leakage). If the battery is almost dead, if you leave it like this for a month, it may all be discharged. Leaving overflowing electricity is the most damaging battery. After leaving it for 3 days or 1 week, the battery will start to bloat. You will find that the flight is weak, but the measured voltage is normal. Therefore, current chargers, such as B6, have a special storage mode. The charger will automatically discharge or charge according to the battery voltage, and stop the battery after it is at 3.8V. Disclaimer: Some pictures and content of articles published on this site are from the Internet, if there is any infringement, please contact to delete. Previous: Introduction to Ni-MH battery performance indicators