Hey everyone, Micah here. Thanks for the kind words as well as the constructive feedback.
I just wanted to point out a couple things. Regarding pricing, I've tried to make this the most affordable way to get an ebike battery, outside of spot welding one yourself if you already own a spot welder. (If you don't own a spot welder already, then this should still be cheaper than buying one in most cases).
In response to HarryS above, $459 for a 13s4p pack is truly an amazing price. I'm not sure where you can find that outside of a Chinese supplier, since Luna (the best deal on packs with genuine high quality cells like these) sells that pack for around $500 including shipping. So I could be wrong, but I still feel my $379 13s3p pack is a good deal, and over $100 cheaper than any other domestic option with the same high quality GA cells. For someone that needs the higher power output or longer range of 4p then the Luna battery would be a better buy, but my kits were designed for people that need not more than 30A continuous, which I think includes most ebikers. And if higher range is needed, the 13s6p kit I made for 20AH with Panasonic 18650B cells for $549 is a very good deal, in my opinion. The same pack (but with GA) cells would be over $200 more from the above supplier, but who really needs 6p of GA cells? 60A continuous is more than the BMS can handle anyways.
I could have gone with cheaper cells like some have suggested, and thus had cheaper kits, but the whole point of this project was to use high quality cells, not off-brand or cheap cells. But if you think I'm "a grinch" then I of course can't change your mind.
In response to Battman, you're absolutely right that there are other ways to build a battery and other sources for cells. What I've tried to do is a build a kit that gives an affordable and convenient way to get everything you need in one place. Many of these parts are hard to find, especially in small quantities. A first time battery builder is likely to end up with counterfeit cells if they just order from random suppliers in China. Buying things like high quality silicone wire, large diameter heat shrink and connectors in small quantities is hard to find, so you're often stuck buying a meter of heat shrink when you need 10 inches, or a bag of connectors when you need only one. This all makes it more expensive to build a single pack. A casual glance might make someone say "hey, these kits seem expensive" but when you do the math and add in the shipping costs for all the parts you'd have to find on your own (my prices included free shipping) then you realize that this is one of the cheapest and definitely the most convenient way to build a battery. Again, I'm not going to change your mind and I don't intend to, I just want to make sure I get a chance to correct the misinformation.
Oh and it's perfectly fine to solder on the nickel strips attached to the cells, provided you do it correctly and don't hang out on the cells for long periods of time. Every professionally built 18650 pack has the wires soldered to the nickel strip. Here are instructions I've written to show people the proper way to build these packs:
http://www.diybatteries.com/2016/10/22/how-to-build-a-48v-10ah-battery-with-maker-batteries/
as well as video instructions that show the proper way to solder them here: