aethyr wrote:I did another experiment.
Theories are subjugated by laws, you experiments don't change the laws of physics, or what happens to a heated cell. Manufacturers experiments have been done under laboratory conditions by engineers and the standards have been set. There's no value to experiments with no standards that fly in the face of everything the manufacturers have learned and discovered using the LAWS of physics. Soldering cells is a bad idea. Period.
If there was a dime for every bloke that came here knowing better I could afford a whole new bike.
Actually, laws of physics simply state the behavior and theory attempts to explain why something behaves as it does. For example, Newton's law of gravity states that anything with mass will attract to each other with a force dependent on their mass and distance between them. That law doesn't attempt to explain WHY particles attract to each other based on mass and distance, only that it does. Various theories exist to try to explain why. Theories and laws work together
Nothing I've done contradicts whatever the engineers have done. Specific heat and thermal capacity is physics/chemistry. As an engineer myself, I know what we publish to the public and what we engineer are often quite different, for many reasons, both legal and from an engineering standpoint. We often over engineer beyond the specs of the product and if some area hasn't been over engineered, we simply say don't use or do something to that area.
For example, it could very well be that soldering for under 5 seconds is perfectly fine, but 10 seconds becomes questionable, depending on temp and wattage of the iron. Its better from a legal and engineering standpoint to simply say: "don't solder", because you can't control HOW people solder and all the different soldering variables. And since battery safety mechanisms are based on heat and pressure response, its difficult to engineer the battery to be safe AND handle high, prolonged soldering temps. Therefore, a cell simply has no over engineered heat tolerance and so they have to disavow any heat application to the cell as part of its published specs.
Second, I'm not entirely convinced they've done a lot of experiments on soldering vs welding. If you look at the datasheets for sony or samsung, they publish various torture tests - overvolting, shorting, dropping, high temps, low temps in great detail. Do they publish that level of detail for soldering vs welding? No, they don't. They simply say don't solder.
I've found only one statement that only briefly explains why not to solder http://www.hurt.com.pl/prods/bat/_li_ion/ncr18650ga.pdf
Do not directly solder to the battery.
Soldering directly to the battery could melt the separator or damage the gas release vent or other
safety mechanisms. This may cause the battery to generate heat, smoke, catch fire, or explode
Note, there is nothing about how soldering will damage to the cell chemistry and cause capacity loss, but rather that it could compromise the safety mechanisms that are heat sensitive. Now that's a valid issue, and I will try to test this. In fact, I plan to cut open a cell, apply soldering heat to the cap and measure the temperature and observe any damage to the gaskets and venting mechanisms.
But I thoroughly do not believe that the battery chemistry can be harmed from proper, quick soldering because of the very laws of physics which dictate how heat distributes and is stored in a material.
In the end, I'm simply showing my findings. If you don't ever want to solder, don't. As for me, I have high discharge cells that need more than a single strip of nickel to transmit that current, so I needed to solve this in some way. And I fully admit I could be wrong and my pack will blow up.