18650 lithium battery modification - two pieces: parallel connection or series connection
I. The Core Difference Between Parallel and Series Connections
If you want to expand one 18650 lithium battery into two, first understand the fundamental differences between these two connection methods:
Parallel connection: Connect the positive pole to the positive pole and the negative pole to the negative pole.
The voltage remains constant (3.7V)
Capacity addition (e.g. 2000mAh × 2)
Suitable for devices that require long-term power supply
Series connection: Connect the positive terminal to the negative terminal to form a circuit.
Voltage superposition (3.7V × 2 = 7.4V)
Capacity remains unchanged (it is still the capacity of a single unit)
Suitable for electrical appliances that require higher voltages
II. Select the connection method according to your needs
Make a choice based on the characteristics of your electrical devices:
Electric tools / drones: Usually require high voltage to drive the motor, and the option of series connection is chosen.
Portable power supply / lighting equipment: For longer battery life, choose parallel connection.
Special equipment: When both high voltage and large capacity are required simultaneously, a hybrid connection scheme can be adopted.
III. Safety Modification Precautions
When operating, keep these life-saving details in mind:
Use batteries of the same model and batch, and avoid differences in internal resistance.
Control the temperature during welding (for spot welding is recommended) to prevent damage to the battery cells.
Install protective plates to prevent overcharging and overdischarging
After assembly, test the voltage balance and leave it to stand for 24 hours for observation.
First use in an air-conditioned environment to avoid abnormal overheating
