6S1P Drone Battery Using Copper Tabs

[SideWinder]

I have built a 6S1P Li-Ion battery pack using EVE 40PL 21700 batteries. These cells have a maximum discharge rating of 70A and a typical discharge rating of 50A. Because of this, I chose to use copper strips instead of nickel strips. Specifically, I used 10mm wide, 0.1mm thick copper strips with a 0.2mm nickel strip layered on top. For the XT60 connector, I ended up soldering the connection, even though it was something I initially wanted to avoid. However, I had concerns about the strength of the spot welds, so I opted for soldering instead. To minimize heat exposure, I took precautions to keep the battery as cool as possible while soldering.


I would like to share some images of my work and get your feedback. Before building this pack, I benefited from many posts here, and I also got the idea for the copper-nickel sandwich from this platform.

(I won’t leave the battery like this; I will cover it with shrink tubing.)

Spoiler: Rest of the Pictures

 

[Zambam]

What spot welder did you use? I am no expert but notice you have more welds per cell than I normally see. What's your reason for doing that? Are these tabless? I recall reading that there is a "no weld" zone in the center.

 

[SideWinder]

What spot welder did you use? I am no expert but notice you have more welds per cell than I normally see. What's your reason for doing that? Are these tabless? I recall reading that there is a "no weld" zone in the center.

More welds are due to copper sheets used. Spot welding with copper is more difficult compared to nickel strips. So, to ensure strong adhesion and achieve proper contacts between cell and copper, I opted to make more welding points.

Also EVE 40PL cells that I used are using tabless design and there are no “no weld zone” I remember.

 

[SideWinder]

Also I’m using homemade spot welder which have microwave transformer, current controller and timer circuit.

 

[Zambam]

Also I’m using homemade spot welder which have microwave transformer, current controller and timer circuit.

Can you post a pic of your homemade spot welder? Do you know how many amps it is capable of?

Edit: What kind of drone and have you flight tested your battery?