Just a li-ion performance consideration I've run into using cheap 18650 lithiums that other folks have noted with Thundersky cells too. My batteries are spec'd for 1.5C, but only provide 1C at less than 50F.
The internal resistance of the 2003 Thunder Sky TS-LP8581A 100 AH
cells in my electric motorcycle was always high enough to cause
embarrassingly slow hill-climbing in cold weather unless I kept them
near full charge in winter. It gradually increased by about 50% to
become VERY embarrassing in cold weather. I noticed that on Thunder
Sky's web site the maximum current rating of the equivalent TS-
LCP100AHA cells is now much higher. I phoned Dennis Doerffel of
REAPSystems to ask for his views about this, and he said that there
was indeed a great improvement. He also said he had some new cells in
stock. I have now bought a new set from him. They are a vast
improvement even on what the previous cells could do when they were
new. They will easily give over 100A at half charge and a temperature
of about 2 deg.C. The old ones would give no more than 15A under
these conditions, even when they were new, although they would give
over 100A on a warm summer day. The internal resistance of the old
cells varied by a factor of about 3 between the best and worst, and
it also increased considerably over the first minute or so after a
load was applied. The new cells are all almost identical and also
their resistance does not increase with time after a load is applied.
I think Thunder Sky have abolished the only real drawback that
their batteries had.