Are you always able to come across this kind of video or article？Many news articles and videos are telling you that lithium batteries are not safe; they are prone to catching fire, exploding, and being uncontrollable. But what is the real situation? In Shanghai, China, on the other side of the Pacific, one out of every three vehicles on the road is powered by lithium batteries. Everything seems to be in order, and lithium batteries have already integrated into their daily lives.
In fact, over a hundred years ago, when cars were just invented, people also thought of cars as monsters. They made too much noise and frightened horses, often drawing ridicule and threats from pedestrians and cart drivers. Initially, the manufacturing process of cars was immature, and their quality was unreliable, resulting in frequent stops and starts. Car manufacturers were often mocked and looked down upon. But over a hundred years later, do you still think the same? Can people's lives still function without cars?
Lithium batteries are similar. New species are always rejected at first, with various shortcomings, but they always quickly integrate into our lives. I want to tell you that you don't need to worry too much about the safety of lithium batteries because they are backed by powerful safety technology. Lithium batteries have overcharge protection, and they also have dual protection: the charger itself has overcharge protection, and the Battery Management System (BMS) also has overcharge protection.
The overcharge protection function of the charger can ensure that the entire battery pack is not overcharged, protecting the safety of the battery. The overcharge protection function of the BMS is more detailed; it can monitor the voltage of each individual cell within the battery, preventing each cell from being overcharged, especially when there is a voltage difference within the battery pack, highlighting its importance.
For example, in a group of lithium iron phosphate battery packs, the full charge voltage is 58.4V. When the charger detects that the battery voltage has reached 58.4V, it will trigger the power-off protection. However, if there is a large voltage difference between the individual cells within this battery pack, the power-off protection of the charger will fail. This is because during the charging process, each cell charges at different rates, with varying voltages—some cells may have already exceeded the full charge voltage, while others have not reached it, resulting in the overall battery pack voltage being lower than 58.4V. In this case, the charger will not trigger the power-off protection. If the BMS does not activate overcharge protection for individual cells, a situation may arise where cells that have already reached full charge continue to be charged, which can easily lead to safety accidents.
So, how does the BMS monitor each individual cell? Lithium battery packs consist of multiple cells, connected in series and parallel to meet our voltage and capacity requirements. The BMS connects to the positive and negative terminals of each cell, forming a closed circuit, allowing the BMS to obtain the voltage information of each cell and transmit it to the control circuit for processing. When the BMS detects that the voltage of any individual cell is approaching or reaching an overcharged state, the control circuit will immediately take measures to stop the flow of current, preventing the cell from continuing to charge, thus protecting the safety of the battery. Through the dual overcharge protection of the charger and BMS, we can effectively protect the battery's lifespan and safety, extend the battery's usage time, and reduce the risk of accidents.
Of course, it cannot be denied that lithium batteries still have technical issues waiting to be resolved, but these issues are no longer the main obstacles to their use. With the rapid decline in the cost of lithium batteries and the increasing maturity of technology, lithium-ion batteries are becoming an important energy carrier.
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Published on: Dec 28, 2023
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