Precautions for parallel connection of lithium-ion batteries
When connecting lithium-ion batteries in parallel, battery consistency is a crucial factor. Poor consistency in parallel lithium-ion battery packs can lead to issues such as failure to charge or overcharging during the charging process.
This would significantly damage the structure of the lithium-ion battery, affecting the lifespan of the entire battery pack. Therefore, lithium-ion batteries connected in parallel in a lithium-ion battery pack are mostly of the same capacity and produced in the same batch.
If you want to connect lithium-ion batteries in parallel, you should pay attention to maintaining the consistency of the batteries. It is best to meet the following requirements: the voltage difference of lithium-ion battery cells ≤10mV, the internal resistance difference ≤5m, and the capacity difference ≤20mA.
Features of parallel lithium-ion battery pack charging
The overall voltage remains unchanged, but the capacity of the lithium-ion battery packs will increase, the internal resistance will decrease, and the power supply delay time will be extended.
The core concept of parallel charging lies in the magnitude of the current after parallel connection and its application. According to parallel theory, the main circuit current is equal to the sum of the currents in each branch. Therefore, for n parallel lithium-ion batteries already combined into a battery pack to achieve the same charging efficiency as a single battery, the charging current should be the sum of the currents of the n lithium-ion batteries. Under Ohm's law: I=U/R, this design is reasonable.
However, the internal resistance of the batteries will change after parallel connection. According to the formula for parallel internal resistance, the total internal resistance of two parallel lithium-ion batteries is equal to the ratio of the product of the internal resistances of the two batteries to the sum of their internal resistances. The parallel resistance decreases as the number of parallel batteries increases. Therefore, the efficiency of parallel charging of lithium-ion batteries can be achieved with a current less than the sum of the currents of n parallel lithium-ion batteries.
If you purchase a lithium-ion battery pack that is connected in parallel, there aren't many things to pay attention to when charging it; just charge it according to the normal charging method. However, if you've manually connected multiple individual lithium-ion batteries in parallel to create a lithium-ion battery pack, then you need to pay attention to the installation of the protection board. Properly installing the protection board will minimize any damage to the lithium-ion batteries during charging.
