how to make a 3-string 12V lithium battery pack.

I recently put together a 3-string 12V battery pack using 1800mAh 18650 lithium batteries, and I want to share a straightforward method to make it yourself. Follow these steps carefully, and you’ll have a stable, functional battery pack in no time.

Materials Needed

• Three 1800mAh 18650 lithium batteries
• Nickel strips
• Hot glue gun
• Lithium battery protection circuit board (BMS)
• Soldering iron and solder

Step 1: Identify Battery Terminals

The first thing I do is check each battery for its positive (+) and negative (-) terminals. Most 18650 batteries have markings on the top and bottom, so make sure these are clearly visible. Correctly identifying the terminals will make assembly much easier.

Step 2: Arrange Batteries in Series

Next, I arrange the batteries in a series connection:

1. Place the first battery with the positive terminal facing up.
2. Flip the second battery so its negative terminal faces up.
3. Place the third battery with the positive terminal facing up again.

This setup creates a proper series connection, adding the voltages together to get close to 12V.

Step 3: Secure the Batteries

To keep everything stable during soldering, I use a hot glue gun to fix the batteries together. Making sure they’re aligned properly prevents shifting and ensures easier soldering later.

Step 4: Connect the Batteries

Now comes the soldering part. Using nickel strips, I connect the batteries:

• Solder a nickel strip between the positive terminal of the first battery and the negative terminal of the second battery.
• Solder a nickel strip between the positive terminal of the second battery and the negative terminal of the third battery.
• Repeat underneath the batteries if necessary for extra stability.

Tip: Keep a steady hand while soldering to avoid short circuits or damaging the batteries.

Step 5: Mark Battery Voltage Points

It’s helpful to mark the voltage points on the battery pack:

• First nickel strip: 3.7V
• Second nickel strip: 7.4V
• Third nickel strip: 11.1V → serves as the 12V output terminal

This labeling makes it easier to connect the protection board correctly.

Step 6: Connect the Lithium Battery Protection Circuit Board (BMS)

Safety is key, so I always connect a protection circuit board. Here’s how I wire it:

• Solder the 3.7V terminal of the BMS to the 3.7V nickel strip.
• Solder the 7.4V terminal of the BMS to the 7.4V nickel strip.
• Solder the B- terminal of the BMS to the 0V terminal.
• Solder the 11.1V terminal of the BMS to the 12V output terminal.

Once connected, your 12V battery pack is ready to use. This pack provides a stable power supply for various electronic devices.

By following these steps, I successfully built a 12V lithium battery pack from three 18650 cells. This method is simple yet reliable, and I highly recommend it for anyone looking to assemble a compact, efficient battery pack.

If you try it yourself and run into any issues, feel free to leave a comment and we can troubleshoot together.

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