The two most important points of lithium battery assembly process.
Many people believe that welding lithium battery cells together is equivalent to a lithium battery? Isn't this easy to do? The application of lithium batteries in the market is gradually becoming more and more widespread, and many businesses that are optimistic about the lithium battery industry have begun to purchase and sell. However, in order to obtain more profit margins, assembling lithium batteries has become the best choice for major businesses. It's easy to assemble lithium batteries, but it's not as simple as friends imagine to make them work well and last for a long time!
Due to the fact that the lithium battery market is in a period of development, personal assembly and manufacturing technology is not yet fully perfected. In order to ensure safer production, systematic technical learning is essential. To learn more about lithium battery technology, please pay attention to the official account. Two important points for assembling lithium battery packs are:
1、 Battery cell
2、 Spot welding
These two points are not up to par, either the battery life produced is very short, or the range deteriorates quickly, and the consequences of virtual soldering and leakage soldering are even more serious. Using three no battery cells and assembling batteries to deceive people, they create so-called lithium batteries that can only be used at the time and cannot even handle lead-acid batteries. If they use good battery cells to make batteries that are not as long-lasting as our ordinary battery cells, they don't care if you can use them for a long time and deceive you without negotiation. If you really want to make lithium batteries safe, stable, long-lasting, slow to decay, and not use three no battery cells, it's not that simple.
Before assembling lithium battery cells into a battery pack, precise pairing of voltage/resistance/capacitance is often required to maximize the effectiveness of each battery cell; The result of no precise pairing is that the battery pack will output the worst battery cell (or string) to the outside world, which is the barrel effect.
Many people think that the purchased battery cells are pre packaged by distributors (some self proclaimed "manufacturers") without the need for testing, and can be directly installed. Leaving aside the full inspection for now, at least you need to conduct random checks, otherwise the mentality of seeking quick success and instant benefits will only make you constantly provide after-sales service for batteries in the future.
Never assemble any battery pack with the mentality of cutting corners. The necessary auxiliary materials must be used and go through a series of steps such as capacity sorting, spot welding, testing, aging, etc.
Application example of 16 channel 5V10A lithium battery detection and capacity balancing instrument
The inconsistency of lithium battery parameters mainly refers to the inconsistency of capacity, internal resistance, and open circuit voltage. Using inconsistent battery cell strings together can result in the following issues:
1) Capacity loss occurs when individual cells form a battery pack, and the capacity follows the "bucket principle". The capacity of the worst cell determines the overall capacity of the battery pack.
In order to prevent overcharging and overdischarging of the battery, the logic of the battery management system is set as follows: during discharge, when the lowest cell voltage reaches the discharge cut-off voltage, the entire battery pack stops discharging; When charging, stop charging when the highest cell voltage reaches the charging cut-off voltage.
Take two batteries connected in series as an example. One battery has a capacity of C, while the other has a capacity of only 0.9C. Series connection, where two batteries pass the same amount of current.
When charging, the battery with a small capacity must be fully charged first, reaching the charging cut-off condition, and the system will no longer continue charging. When discharging, batteries with small capacity will inevitably release all available energy first, and the system will immediately stop discharging.
In this way, small capacity cells are always fully charged and discharged, while large capacity cells continue to use a portion of their capacity. There is always a portion of the capacity of the entire battery pack that is idle
2) Life loss, similarly, the lifespan of a battery pack is determined by the cell with the shortest lifespan. Most likely, the battery with the shortest lifespan is the one with the smallest capacity. Small capacity battery cells, always fully charged and discharged, with excessive output, are likely to reach the key point of their lifespan first. When the lifespan of a battery cell comes to an end, a group of battery cells welded together also come to an end.
3) As the internal resistance increases, cells with higher internal resistance generate relatively more heat when the same current flows through them. The high temperature of the battery accelerates the degradation rate and further increases the internal resistance. Internal resistance and temperature rise form a pair of negative feedback, accelerating the degradation of high internal resistance cells.
The above three parameters are not completely independent. Cells with deep aging have higher internal resistance and more capacity decay. Separate explanations are just to clarify their respective directions of influence.
