To make a 12V battery pack using 18650 lithium-ion batteries, you will need to connect several of these batteries in series. The 18650 lithium-ion battery typically has a nominal voltage of 3.7V. To achieve a 12V voltage, you need to connect four of these batteries in series.
The basic principle of connecting batteries in series is to connect the positive terminal of one battery to the negative terminal of the next battery, and so on.
This way, the voltage of each battery adds up. Thus, four 3.7V 18650 lithium-ion batteries connected in series will result in a total voltage of 4 x 3.7V = 14.8V. This voltage is slightly higher than the required 12V, but it is generally acceptable since many devices can operate within a certain voltage range.
When connecting batteries in series, keep the following points in mind:
Ensure that all batteries are new or have a similar discharge state to avoid large voltage differences during charging or discharging.
Use appropriate battery protection circuits to prevent overcharging, over-discharging, overcurrent, or short circuits.
Use suitable wires and connectors to ensure a smooth current flow and to avoid excessive heat or resistance.
Finally, follow all relevant safety regulations and guidelines to ensure safety during the assembly and use of the battery pack.
Please note that while making a battery pack can be an interesting project, it also carries certain risks. Be cautious and make sure you understand all relevant safety knowledge and regulations.
Today, we will use idle 18650 batteries to assemble a 12V battery pack.

First, arrange the batteries and add an insulating layer in between to prevent short circuits.


Next, weld nickel strips onto the battery pack, and then wrap the entire battery pack with insulating Kapton tape, and tape it to increase sturdiness.

Now we can install the protection board onto the battery pack. First, attach double-sided tape to the protection board, then solder the protection board wiring.


After soldering, use a multimeter to test the battery pack’s output voltage.

Once confirmed, insulate the entire battery pack, solder the output and charging wires, and finally use a 12V charger to charge the battery pack.

Test if the battery works normally and conduct discharge testing.


Finally, wrap the battery pack with Heat shrink film to make it more secure and apply waterproof glue.



The 12V battery pack assembly is now complete!
Making a 12V battery pack requires a certain level of technical and safety knowledge, but by following the correct methods and precautions, you can successfully create a stable and reliable battery pack. If you are interested in electronics, you can try making a battery pack yourself. However, be aware that improper handling of lithium-ion batteries can be dangerous. Please be cautious and make sure you understand all relevant safety knowledge and regulations.