Maximizing the capacity/energy efficiency of a battery pack refers to setting all the cells connected in series in the pack to the same SOC even if they have different capacities. Manage the SOC at all times to maximize the output energy of the battery pack. In order to maximize the output energy of the battery pack, all battery cells must be fully charged. That is, the SOC of all batteries must be 100%. If the batteries have different capacities, some batteries will charge/discharge more than others. For example, suppose a battery pack has three cells connected in series, C1>C2=C3. The only way to equalize this pack is to apply a differential charge current to the higher capacity cell (C1). This must also be true when the battery pack is discharging, otherwise when the smallest cell reaches the shutdown voltage, the entire pack stops discharging while the other cells still have capacity remaining, reducing the overall capacity. Over time, the battery with the smallest capacity will degrade faster than the others, accelerating capacity loss over many charge/discharge cycles. By matching the voltage of the batteries in series, more current will be drawn from the high capacity battery. When discharging, it is required to consume some extra voltage through equalization. In the end, when all batteries reach 0SOC, the total power obtained from the battery pack will still increase compared to before equalization. Generally, the quality control of cylindrical lithium-ion batteries (cylindrical cells) is usually good, and the difference in battery capacity does not exceed ±3%. The input capacity is basically more accurate, the difference is not more than a few mAs (milliampere seconds). Therefore, the absolute value of the battery capacity is also basically accurate, and the difference in SOC is within a few percentage points. The chemical properties of lithium-ion materials themselves do not cause battery imbalance, nor do they have a reversible self-discharge mechanism. However, lithium-ion batteries must also go through a process to stabilize performance, and will produce irreversible losses, most of which occur before the batteries leave the factory. A small amount of this kind of irreversible loss will also occur after high-temperature discharge and long-term storage at room temperature, and the maximum proportion of this loss is within 10%. All batteries in storage or in use at the same time have the same probability of this loss, so this situation will not cause battery imbalance problems.see more:12v 500ah lithium ion battery When irreversible loss occurs, it is accompanied by a small amount of reversible loss, and there is a certain proportional relationship between the two. Most of the reversible loss that occurs in the factory has been recharged before the battery capacity is sorted, so this kind of loss is very small, and it is the same for each battery, so it will not cause battery imbalance problems. Another cause of battery imbalance is that the battery has been idle for too long before assembly, and if several batches of batteries with different production times are put into the same battery pack, this imbalance will be aggravated. In this case, batteries with different reversible losses sorted by capacity but not yet assembled will accumulate larger differences over time. Even after being assembled into a battery pack, if the cells in the pack vary greatly (especially if the pack is left for too long), the cell imbalance within the pack will increase over time.