Spring Issue, Bolt Issue, Vibration Issue, Battery Life, Amp Issue
I have not purchased any kits yet because I saw a video of users having the batteries slip out of the trays and the zip ties not being strong enough to keep them together and not being able to handle enough amps. A few modifications you could do would be to just remove the springs and use straight metal contacts which would eliminate batteries getting pushed out with zip ties right? or perhaps you could make 2 adapter plates with 4 bolts to hold down a pack on the ends? Anyways the real reason why I have not bought the kits yet is I want to know how you know when a battery cell is bad. Because while the design is cool with not having to solder/spot weld, if the batteries are connected in series/parallel, how do you know what battery is bad since if you put the tester contacts on the ends it will read the voltage of all the cells right? Let me know, thanks. Also I have heard of people taking batteries out of old laptop battery packs. Why exactly would those batteries work when the laptop says they are not holding a charge anymore. Are you saying that what goes bad is the laptops charging circuit? and the 18650s inside them last indefinitely? How many years do they last? Id like to be a good customer of yours, thanks.
The reinforcement plates to provide pressure are called sandwich plates and they are a part of the build process for vibration-heavy environments: https://vruzend.com/adding-sandwich-plates-to-ensure-continuous-connections/
People sometimes salvage cells from laptop batteries because it is much cheaper than buying new cells. Often laptops die before the batteries, and people throw the whole thing out together. So recycling centers fill up with laptop batteries that still have some life left. While these cells can be salvaged sometimes, they are low power and not great for things like e-bikes unless you use a lot of them. They are better for high parallel count packs like DIY powerwalls, or low power applications.
To determine if a cell is bad, you'd need to remove the parallel connections to the cells. This is true whether you use the Vruzend system or spot weld or any other battery connection method. It's just that with Vruzend kits, it is much easier to remove connections since they are not permanent.