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Multi-cell lithium-ion battery storage technology security risks I
日期:[2012-7-14 9:07:27]   共阅[1139]次

  These imbalances will not only cell tolerance quantity is small, and even may cause severe overcharge, over discharge and other security risks. Let's undertake a careful analysis of these two: The first is for the case of small cell tolerance quantitative;. To third-string battery pack applications, for example, initially, A, B, C three single battery are 100% capacity, but in the long period of use, each battery is produced is not balanced, resulting in a moment, A 80% of remaining battery capacity, B the remaining 40% of battery capacity, C 60% battery remaining capacity; At this time of the battery pack for charging, because over the role of high-pressure protection, when A full 100% battery charger off when leaving, B battery capacity only to 60%, C 80% battery capacity, which appear within the battery pack B cells and C cells are not fully charged phenomenon. In the discharge of the battery pack, due to over voltage protection function, when the B cell is discharged to 0% (ideal value), A will have 40% battery capacity, C batteries and 20% capacity, there A battery and battery pack has not C battery is discharged phenomenon. (Third-string balance after battery charge / discharge capacity changes as shown in Table 1).

  Secondly, for the potential to cause serious over charge, over discharge conditions. Battery pack, for example with 4 strings (single point of over-voltage 4.2V; voltage point of 3.0V; only the total voltage of the battery pack protection, without single battery voltage monitor in Figure 1), the prolonged use , the battery had not balanced. No single case of battery voltage monitoring, discharge, although the battery pack to meet the 12V undervoltage protection settings, but it is 3.6V +3.2 V +3.2 V +2.0 V = 12V, of which a minimum balance battery voltage as low as 2.0V, a serious over-discharge phenomenon. Charge, although a 16.8V over-voltage protection setting to meet, but 4.7V +4.1 V +4.1 V +3.9 V = 16.8V, of which the battery voltage has reached the highest imbalance 4.7V, this is a very dangerous phenomenon of overcharge.

Balanced approach potential resistance

  Understand the reasons causing the battery is not balanced and weaknesses, we have a balanced program in the design of the battery should be considered a proper balance current size, consider balancing the timing of the action, consider the cell balancing accuracy, consider the number of battery with a balanced, considering the overall balanced design thermal problem.

  Now, how economic and reliable solution to multi-cell battery pack in the single problem of imbalance of power tools, electric bicycles, light electric vehicle applications such as the promotion has become increasingly important. There are many ways theoretically balanced, which, resistor (shunt) is a balanced approach is considered the most economical and practical way. In this basis, the latest bump technology made the smart balancing Battery Bleeding-on-Demand (BOD) technology. The balanced technology provides the parameter settings are all designed to balance the battery when considered as part of the overall heat. Restrictions on the balanced application of high heat loss, choose a balanced low current, high voltage start a balanced, lower accuracy and less at the same time balancing the number of batteries to reduce the balance balance heat loss; and heat capacity of the battery pack off the case , you can choose a higher current balance, the balance starts low voltage, high accuracy and balance are more balanced, while the number of batteries to improve the balance of speed.

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