finnishsnowmobiler said:
Hi,
I procrastinated many weeks about whether or not to solder 18650 batteries. I tried many combinations (solder, wire and flux / acid) to find the quickest method to solder these cells together. I’m pretty proud of the outcome (less than one second contact time and to tear the connection apart you need really significant forces and the battery can gives up millimeter or two when applying a huge pull)
Items needed: A quality 80w soldering iron Lötwasser (soldering acid) Stranded copper wire, Leaded solder The actual cells
What I couldn’t demonstrate in the video is how I applied pressure to the joint with a wooden block to really maximize the surface area of the contact. Please enjoy the short video!
finnishsnowmobiler,
Sorry man, but you will
never get all of the acid flux out of that stranded copper wire. The remaining acid will slowly destroy the copper. I could see using thick solid copper wire there, instead. You could bend the round wire into a small OMEGA ( Ω ) shape for each cell, for a better contact area. You could even flatten the round wire slightly at the OMEGA by putting it between two small thick metal squares and striking the metal squares
once with a light hammer. Practice helps, with the hammer.
Keep a damp sponge at hand on the table, so you can wipe the soldering iron tip clean, bright and shiny, just before each soldering operation. Solder which has been on the soldering iron tip for more than thirty seconds will be oxidized and dull. The correct process is to apply solder to the soldering iron tip, quickly wipe the tip clean on the sponge, apply fresh solder to the tip, and then make the connection.
To make a rapid solder connection, first use very fine sandpaper (gently) to clean the metal. Wipe away the dust, and apply a little flux. Use the soldering iron to quickly deposit a very thin layer of melted solder on the cell top, and on the copper wire. When ready, place the copper wire on the cell top, refresh the soldering iron tip on the sponge, add solder, and apply the iron to the work. As quickly as you can melt the solder on the cell, the work is done and remove the iron.
The solder left on the work should be smooth and shiny. Clean away excess flux with a stiff brush and liquid. For my favorite flux, the liquid needed is just water.
It helps to practice the work on a dead cell, so you can repeat the practice until proficient. Your "pressure with the wood block" is a good idea for this work.
Materials:
Common lead solder: it is typically 60/40 as a tin/lead ratio. 63/37 solder (SN63) melts faster, at the lowest possible temperature, of all the tin/lead solders. This is the good stuff, if you can get it. 60/40 solder will certainly do the job, though. I do not recommend any flux-core solders.
Flux: I do not know where you are located, but in the USA, LA-CO solder paste flux is non-acid, and the cleanup is done with water only, no chemicals needed. It is even safe for "drinking water" copper pipes. This flux can enable the soldering of many different metals which usually are not soldered. Look at the bottom of this web page (linked below) for RESOURCES/FIND A SELLER.
https://markal.com/products/regular-flux-paste?variant=9204786757679
Best wishes . . .
. . . 8) . . .
