18650 Battery Pack

• Cell insulation: Insulate each cell with specialized fish paper. 
• 
  Arrange the 18650 cells according to the series and parallel requirements, preferably using a fixed holder to prevent the cells from moving. 

• Use nickel strips and a welding machine to weld the batteries. In series connections, connect the positive terminal of one cell to the negative terminal of the next cell. In parallel connections, connect the positive terminal of one cell to the positive terminal of the next cell to form the required battery module. 

• Weld the protection board to the main positive and main negative terminals of the cells. If there are communication wires, connect them in a specific order to ensure the welding is secure and not easily dislodged. 

• Wrap the battery pack with PVC or place it in a battery case, securing it with hot melt glue or 3M tape. Ensure the battery has some space for heat dissipation. 

• Use a multimeter to test the voltage and internal resistance of the entire battery pack to ensure normal output.

This is an example of a 12V battery pack made from 18650 cells, following the DIY battery pack process.

1. Preparation

   • Insulate the positive terminal of each cell with fish paper.
   • Use a multimeter to test the voltage of each cell, ensuring their voltage and internal resistance are consistent. It's best to also test the capacity to ensure minimal differences in these three values among the cells.
     
     

2. Design the Battery Pack Configuration

   • This is a 3-series battery pack, resulting in a nominal voltage of 11.1V after connecting in series.
     
     

3. Welding the Batteries

   • Use nickel strips and a spot welding machine to weld the batteries together. In series connections, connect the positive terminal of one cell to the negative terminal of the next cell, linking end-to-end.
     
     

4. Install the Battery Protection Circuit (PCM)

   • Its role is to protect the battery from overcharging, over-discharging, short circuits, and to balance the cells. Connect the PCM to the battery pack, ensuring each connection is secure and reliable. The wiring design should be simple, reasonable, and effective.
     
     

5. Assemble the Battery Pack

   • Place the welded battery pack into a battery case, or use hot melt glue to fix the batteries together. Ensure there is enough space between the batteries for heat dissipation.
     
     

6. Testing and Charging

   • Use a multimeter to test the voltage of the entire battery pack, ensuring the connections are correct. Use an appropriate charger (such as a 12.6V DC adapter) to charge the battery pack.

When choosing a suitable charger for a 12V 18650 battery pack, consider the following key factors:

Key Factors:

1. Voltage and Current Compatibility

   • Ensure the charger supports the charging voltage and current for a 12V battery pack. Generally, the voltage for a 3-series battery pack is 12.6V, so the charger's voltage should be between 12V and 12.6V.
     
     

2. Charger Output Current

   • Typically, the charger's output current should be about one-third of the battery pack's total capacity. For example, for a 24V 18650 6Ah battery pack, the recommended charger current is 2-3A.
     
     

3. Safety Features

   • Choose a charger with safety features such as overcharge protection, short circuit protection, and reverse polarity protection to ensure safety during the charging process.
     
     

4. Display Function

   • Some chargers come with an LCD display that shows the battery's charging status, voltage, current, and other information, making it easier to monitor the charging process. Some chargers have an indicator light that turns from red to green. The charger lights up red while charging and turns green when fully charged.
     
     

Based on our experience, we recommend using the Nitecore i2 Intellicharge, Xtar VC4SL, or contact us for other recommendations.

• UN38.3 Certification
  
  

  • The main test items include safety tests, altitude simulation, thermal tests, vibration, shock, short circuit, overcharge, and forced discharge. This is a necessary certification for the international transportation of lithium batteries.
    
    

• IEC 62133 Certification
  
  

  • The latest standard is IEC 62133-2:2017. The test content includes short circuit, overcharge, thermal runaway, mechanical shock, vibration, external heating, and impact. This certification is commonly required by European countries.
    
    

• UL2054 Certification
  
  

  • A standard developed by UL Solutions, this certification is for battery packs and is an important certification for the North American market. It is very expensive.
    
    

• CE Certification
  
  

  • This is a mandatory certification required by the European Union, mainly referring to CE-EMC certification, ensuring compliance with health and environmental standards. The CE mark is a necessary condition for entering the European market.
    
    

• RoHS Certification
  
  

  • RoHS usually involves destructive testing. Due to the special nature of batteries, we provide a battery directive instead to ensure that lithium batteries do not contain harmful substances such as lead, mercury, cadmium, etc.
    
    

• UL1642 Certification
  
  

  • This is the UL1642 certification for battery cells.

There are indeed significant differences between different brands of 18650 lithium batteries, mainly in the following aspects:

Quality and Performance

• Renowned international brands like Samsung, LG, Panasonic, and Sony typically excel in battery quality and performance. Now, domestic brands like EVE and Lishen also offer good quality cells and are often the first choice for many power tools and energy storage products.
  
  

Application Fields

• Different brands of 18650 batteries may be optimized for different application scenarios. Some focus on power cells, while others focus on capacity cells.
  
  

Capacity and Performance Parameters

• Various brands of 18650 batteries differ in parameters like capacity, internal resistance, and continuous discharge rate. Some have a 1C rate, some have 3.0C, 5.0C, or even 10.0C rates. The main capacity range is between 1200mAh and 3500mAh.
  
  
• The lower the internal resistance, the stronger the battery's discharge capability. It is generally recommended to choose batteries with an internal resistance below 100mΩ.
  
  

Safety Performance

• High-quality brands usually invest more in safety features. For example, Panasonic's 18650 batteries are used by Tesla and have high safety performance.
  
  

Cycle Life

• Different brands have varying cycle lives. For example, imported cells generally have a cycle life of 800 cycles. The first-tier domestic companies' cells have a cycle life of around 500 cycles. Cheaper cells have a cycle life of around 300 cycles.
  
  

Price

• Imported cells from LG, Samsung, etc., are the most expensive. The higher the discharge rate, the higher the cell price.