Fast Charging of Rechargeable LiPo Battery

The working principle of lipo batteries is mainly to rely on lithium ions to move back and forth between the positive and negative electrodes. Charging the operating current moves lithium ions from the positive electrode to the negative electrode. It is a rapid process for lithium ions to go out of the material and into the material. It’s a slow process. For graphite materials, when lithium ions come out, it is more than a hundred times worse than when they go in, and the speed difference is two orders of magnitude. Discharging is easier, but charging is harder and slower. Therefore, some companies claim “by improving the positive electrode, how much the battery can be fully charged in 5 minutes”, which is completely unbelievable, because it is not the positive electrode that is charged, but the negative electrode.

Today’s rechargeable lipo battery material system includes graphite and other carbon materials for negative electrodes. Recently, I have wanted to add silicon oxide and fast-charge lithium carbonate to it. They all have different characteristics. When a large number of lithium ions are charged, they first pass through and diffuse in the electrolyte, which makes charging at low temperatures problematic because the electrolyte doesn’t have enough electrical horsepower at low temperatures. The diffusion velocity of the ions needs to be exceeded. This gets more complicated if you want to fast charge during the day.

LiPo batteries have two problems when they need to be fixed. Lithium ions cannot be transported in the electrolyte. However, after lithium ions migrate from the electrolyte to the electrode interface, the entry gate is too small for lithium ions to enter. After entering, the room is too crowded after joining, and it is more dangerous at the door. Accumulation at the door can cause a short circuit. The lower the temperature, the greater the problem.

Consumer products require fast charging. If the charging power of ordinary cars is increased, the charging time will be shortened accordingly. It’s not a big deal to be able to achieve a full charge in a few minutes, but if it is within an hour or even half an hour, whether this kind of fast charging is still meaningful depends on whether the lipo battery and charging infrastructure can do it. meet the requirements. This involves security issues.

In addition to safety concerns, fast charging, including charging modes, can affect battery life. Setting the upper voltage limit of the lipo battery a little higher will reduce its life of the lipo battery. When fast charging, a higher temperature can achieve the effect, but it is also at the expense of battery life. It may not be noticeable when the vehicle is first used, but the effect on the battery will become more noticeable as you use it.

Battery life is also related to the depth of charge and discharge. For example, the battery of a mobile phone stops charging when it reaches 90%, and starts charging when it exceeds 20%, which is better than charging every time it is charged and every time it is turned off. Longer, longer. Therefore, lipo batteries are best in the middle.

To give an example of fast charging, the National Laboratory of the United States has used Nissan Leaf to conduct experiments under different charging conditions and temperatures. This is the difference in fees. Through experiments, it is found that if the temperature can better maintain the temperature of the battery, the voltage can also be controlled better, and the impact will not be too significant. There are two conditions for correct fast charging. One is to control the temperature, and the other is not to boost the voltage, it must be done within the voltage range.

To sum up, in addition to speed, fast charging also cares about safety and battery life. Battery life is closely related to the depth of charge and discharge of the battery. Proper charging and proper fast charging will not affect the battery, but high-rate fast charging of lipo batteries will affect lipo batteries.

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