Using Protected 18650 with the Vruzend Battery Kit
I am in the process of building a 14s6p 52v 20ah battery for a three wheel 48v hub motor powered STEM Cycle. I bought your battery kit, actually two since the 84 cells exceed the 52 cell limit of a single kit. After much research, including your you tube channel, I decided to buy protected 18650 cells with the button PC board on the positive end. In our situation battery length is not a factor, but with your battery kit end caps will the protected cells be a fitment problem as far as diameter is concerned or in the push-on compression method of installation for the PC board's integrity. I went through Aliexpress, as you suggested in your videos, and purchased their NCR 2017 Original LiitoKala 18650 3400mAh battery 3.7V Li-ion Rechargebale battery PCB Protected 18650B18650 3400 Properties: Color 6PCS.
Thanks in advance, Barry
The dimensions of the kit should still work fine with protected cells, the cap will just sit a bit higher. However, you should know that protected cells generally aren't a great idea for building multicell packs. They can work, but as soon as the protection circuit fires in one cell, it cuts off an entire series string in some cases, which can cause issues with premature "empty" packs. The protection circuits aren't often of very high quality, so if one fails, it can cause problems with others cutting out.
The reason we are using protected versions is that these are being used in a classroom environment with high school students. We want to ensure that in case of an oops, the student and the shop environment are as safe as possible. The reason for using your kit is for ease of packaging groups of cells so they may be assembled, tested, monitored, and maintained/repaired in a learning environment safely by people on a steep learning curve. We actively monitor, and collect/analyze data to verify behavior under specific maintenance processes for best practices. We have your battery book and are trying to be diligent in proper methods based on your common sense guidance. Thanks for your help.
A short while ago I asked about using your battery kit with protected 18650 cells (see above) where you believed there would be no problem. The first bundle of 36 Liitokala 3.7V 3400mA units arrived yesterday, so I assembled a couple with the kit caps. The first went very well, with the output measuring exactly the same with or without the caps. The second went together pretty well and measured properly on the VOM, but upon further inspection the positive end cap split in one of the female interlock channels where it is the thinest. I used the same gentle compression method on both test cells. Hopefully this is a fluke (no pun intended), and the rest will be better behaved. Do you replace faulty caps that fail on first application? I don't see any icon here that enables uploading a picture, but will gladly provide one where possible. Best to you, Barry