Battery series means the batteries are connected end to end. That is, the anode of the first battery is connected to the cathode of the second battery,and the anode of the second battery is connected to the cathode of the third battery and so on. The purpose is to increase the output voltage. The series voltage is equal to the sum of battery voltage,and the current is equal to the current flowing through each battery. If there is one battery damaged, the entire battery pack will be unusable or voltage dropped.
Battery parallel means the batteries are connected head to head. That is, the anode of all batteries is connected, and the cathode of all batteries is connected. The purpose of parallel capacity is to increase the capacity of battery pack. The parallel voltage is equal to the voltage of a single cell,and the current is equal to the sum of the current of the cell. Although the battery pack's endurance has increased, the damage caused by short-circuit current is more serious.
The characteristics of parallel lithium battery are:the voltage is unchanged, the battery capacity increases,the internal resistance decreases and the power supply time is prolonged. The core of parallel is the magnitude and function of parallel current. Attention should be paid to the consistency of lithium batteries in parallel,because the parallel lithium batteries with poor consistency will fail to charge or overcharge during the charging process, thus the battery structure will be broken and the life of whole battery pack will be shortened.
The difference of battery parallel and series is mainly on the voltage and capacity,for example,the voltage is 3.7V,the capacity is 3000mAh, and take 2 batteries,if series,the battery model will be 7.4V/3000mAh;if parallel, the battery model becomes 3.7V/6000mAh.