How to Assemble a Car Battery Using 18650 Cells？

It is a practical and challenging project to make a car battery with 18650 cells. Because of their high energy density and wide applicability, many DIY enthusiasts and electric car modifiers first turn to the 18650 cells. Below, we will explain how to assemble a car battery using 18650 cells in detail.

I. Materials and Tools Preparation

Before assembly begins, ensure that you have these materials and tools:

18650 Cells: Choose enough new, undamaged 18650 cells according to the required power capacity and voltage.

Cell Sorting & Assembling Instrument: This device is used for screening the voltage, internal resistance, and capacity of cells so as to maintain their homogeneity.

Nickel Strip: Pure nickel nickel strip or nickel-plated steel strip that connect between the cells.

Solder Wire, Solder Pen: For welding positive and negative electrodes of the cell.

Insulating Tape: To wrap around the negative electrode of the cell so as to avoid short circuiting.

Battery Slot or Battery Box: These are for cell fixing and ensuring good heat dissipation as well as insulation.

Protection board; this is helpful in protecting battery pack from abnormal conditions such as overcharge/over discharge

Multimeter; this is used for testing voltage/current of a battery pack

Needle-nose Pliers & Scissors; auxiliary tools for clamping batteries (or cutting insulating tape)

II. Screen and Match Battery Cells

Voltage Screening & Internal Resistance Screening – Use Battery Cell Sorter & Matcher instrument for screening battery cells so that voltage difference within 5mV while internal resistance difference within 3mΩ

Capacity Matching – If possible select similar capacity batteries for matching so that consistency of packs increased.

III. Welding & Assembly Of The Battery Cells

Polarity determination on battery cell – there is positive pole at top edge of 18650 battery cell while negative pole is located at bottom edge. Ensure all batteries have the same polarity direction.

Nickel Strip Welding – Use solder pen and solder wire to attach nickel strip on battery cell’s positive & negative electrode. Watch temperature control and duration, so as not to overheat or cold weld the battery cell while welding is executed.

Battery cell assembly: Take out the welded battery cells from their case according to predetermined arrangement. Provide certain space among cells for heat dissipation purpose.

Connect protection board – According to protection plate’s specification as well as wiring definition diagram, connect cells’ positive & negative poles with protective plates. Pay attention to order of connection and correctness.

IV. Insulation and Testing

Insulation treatment 0: To avoid short-circuiting, use insulating tape wrapping around the part that is negative within the cell. The battery slot should also be insulated both inside it and outside it.

Performance test; using a multimeter test voltage/currency of a battery pack in order to satisfy design requirements; otherwise use lithium battery aging cabinet for more performance testing

V. Safety Precautions

Safety of Operation: Put on safety glasses and gloves when assembling in order to avoid injuring your eyes or hands with an exploding cell during this process.

Battery storage: To prevent danger, don’t subject the cell to high temperature or humidity.

Charge and discharge management: Ensure that right chargers and discharging equipments are used during charging and discharging process of the battery pack for prevention of overcharge or overdischarge.

VI. SUMMARY

The above steps enable you to effectively assemble a car battery using 18650 cells. In this process, it is important to choose similar cells, weld well and insulate properly. Through soundness in these areas can one put together a battery pack that performs consistently while being safe and reliable. I wish you good luck with your project!