01-16-2016, 12:15 AM
I was not commenting on your setup as a whole, although there are comments to be made - balancing may be desirable or mandatory for safety depending on the exact chemistry your 18650 uses (18650 is a form factor, not a chemistry specification), likewise with protection - protection is hard to do properly if you don't have the discharge curves and with cheap no-name batteries you never do. I was simply stating that buying el-cheapo batteries is invariably a bad idea for high discharge applications. Depending on the exact chemistry used, it may not be a fire risk but you might have brownouts or considerably shorter lifespan that makes these batteries more expensive than higher quality, well-branded ones. There's a huge amount of information online about this subject, so it's a bit pointless to rewrite it here. Suffice to say that certain communities like vapers (batteries powering atomizers) and flashlighters have done a huge amount of extensive testing on this, the upshot being that you have every opportunity to use their data to select appropriate batteries.
As a matter of simple math, generic chinese 18650s sold as 3000mAh usually turn out to be in the region of 1000mAh. Since they're usually only capable of 1-1.5C and the curve stops delivering much earlier, you're starting to butt up against it if you place a 2+A load on them. Since you're now running them harder and out of balance as well, chances are you're killing the lifespan and total capacity, screwing the curve even more (although I'm not sure if reduced capacity affects C rating for all chemistries - you need to check datasheets).
This isn't a dig at you and I think people posting their DIY projects and results is awesome. I'm sure people will find yours useful. I'm just pointing out that, in the case of batteries for high discharge applications, paying for quality ends up being cheaper in the medium to long term, safer and considerably more hassle-free.
-p
As a matter of simple math, generic chinese 18650s sold as 3000mAh usually turn out to be in the region of 1000mAh. Since they're usually only capable of 1-1.5C and the curve stops delivering much earlier, you're starting to butt up against it if you place a 2+A load on them. Since you're now running them harder and out of balance as well, chances are you're killing the lifespan and total capacity, screwing the curve even more (although I'm not sure if reduced capacity affects C rating for all chemistries - you need to check datasheets).
This isn't a dig at you and I think people posting their DIY projects and results is awesome. I'm sure people will find yours useful. I'm just pointing out that, in the case of batteries for high discharge applications, paying for quality ends up being cheaper in the medium to long term, safer and considerably more hassle-free.
-p
