Be very careful in any dealings with K2 (formerly Peak battery).
They have repeatedly understated the internal impedance of their previous 26650 cell offerings
to say it nicely.
The prior model cells were sampled, tested using professional instrumentation, and returned room temp I/R numbers in excess of 20mohms @50% SOC. Many cells were tested, with similar results.
Their salesman skirted the I/R results when confronted with the numbers.
Now take on the other hand; LifeBatt
What you have here is a 3x overpriced Taiwanese assembled cell, that may contain some percentage of Phostech licensed powder
the remaining could be dandruff for all we know. The pricing, as we've surmised, has to do with the three year warranty offered (as long as you buy their BMS). The problem is that you'd be required to deal with a person named Don Harmon (douchebag extraordinaire) in the event of a problem, and that's where it will go south
There is some history on this noted on this at another EV forum.
These are very good performing cells, delivering well within their stated impedance and capacity numbers. Isn't it funny? the product appears great, it's the company pitchman who is a trainwreck and can't keep his stories straight.
My advice? go with Headway cells from Victoria. They're relatively cheap, they appear to meet their cycle life numbers, and there is plenty of published data about various builds using them. The I/R numbers are somewhat high for EV use, so put a few more in parallel.