Overcharge and overdischarge of local cells in the battery pack

Overcharge and over-discharge of partial cells of the battery pack (slightly damaged cells) For the convenience of analysis and calculation, suppose there are special conditions with the following technical indicators: 1) Battery pack parameters: 100×2V, nominal capacity 100Ah, of which the actual capacity of the first stage is 97Ah , The actual capacity of the remaining 99 segments is 100Ah; 2) The conventional voltage closed-loop control mode of the power supply equipment parameters, in which the floating charge conversion setting voltage is 240.00V (execution erroru003d0, monomeru003d2.400V), and the discharge termination setting voltage is 170.00V (Execution erroru003d0, single unitu003d1.700V). When the system is running between charging and discharging, there are two special time periods, namely (1) The first special period will appear under uniform charging operation, the starting time is 97h, single cell voltage>2.400v, and total voltage< 240.00v (at this time, the power supply device will continue to be responsible), the end time is the total voltage u003d 240.00v (at this time, the power supply device will accurately perform the unified charging float switch). According to the meaning of battery damage, the 97Ah battery was in an overcharged state during this period, and the other 99100ah batteries were in a safe range. (2) The discharge operation will occur in the second special period. The next time is that the battery voltage is <1.700v from 1997, and the total voltage is >170.00v (the power supply will continue to discharge at this time), and its end time is the total Voltage u003d 170.00v (the battery pack will stop unloading at this time). During this special period of time, the 97Ah battery is in an over-released state, while the remaining 99100ah battery is still working within a safe range. The objective existence of these two special periods will inevitably cause the following problems (1) The equipment is perfect, the control is accurate, and the battery can not be damaged. However, the overcharge and overdischarge of the individual batteries are carried out under overall safe operation. In terms of quantity, the damage rate is only 1%, and the damage time is less than 3%. (2) The difference between the actual system and this example is only the size of the difference in capacity. It only changes the length of the special time period and does not affect the existence of the special time period; this example shows that the battery pack is without exception There are inherent safety hazards, which shows that there is an inevitable internal connection between battery damage and battery accidents. (3) The difference in the parameters of the micro-damage battery. The consequence of the micro-damage is the damage to the original structure and the decrease in the capacity of the energy storage battery. This will further increase the battery's monomer. The consequence is the cause of the future micro-damage. Obviously there is a causal relationship between Therefore, it is reasonable to infer that the consequences of battery damage continue to deepen in the process of time and micro-injury, until the battery completely fails. The failure duration may vary with changes in operating conditions, but it will definitely occur after multiple damages. Accelerate the deterioration until an unavoidable failure result occurs. (4) Of course, the loss time with a damage rate of 1% or 3% is not enough to threaten the safety of the entire backup power system and can only be regarded as a numerical method, but as long as the backup power system is repeatedly charged and discharged, this value The method process will repeat. In other words, the micro-damage process is actually the process of the entire backup power system running. Disclaimer: Some pictures and content of the articles published on this site are from the Internet. If there is any infringement, please contact to delete. Previous: How to repair the mobile phone lithium-ion battery by yourself?