I started delving into this a bit after I went and bought a few Nitecore batteries from that rainforest shopping place... Anyway.
I found flashlight forums to be a pretty good knowledge base here (yes, flashlight enthusiasts, don't smile and point, waver of noisy lightstick
) Anyway, of particular note was this:
http://lygte-info.dk/review/batteries2012/CommonSmallcomparator.phpIt's a comparator for batteries, with quite a few different 14500s represented, including the TrustFires available from UltraSabers.
From
Schtuperman's Anecdote, I surmise that the current draw of an Emerald/Obsidian saber to be in the neighborhood of .75-.85A (probably in the higher end of that range).
The Keeppower 14500 840mAh (described as "one of the best 14500 on the market." in the tester's conclusion)
It has a discharge graph that looks like this:
This battery would probably give 60-65min of runtime for an Emerald/Obsidian saber. On the down side, it is also 1.4mm longer than the Trustfires.
The Trustfire 14500 900mAh (flame) (the flame descriptor is because there's another Trustfire 14500 900mAh... with a blue wrapper (and is apparently junk)).
The (flame) battery is described as "good for a cheap battery, but the voltage under load is considerable lower than the best batteries.")
The discharge graph looks like this:
As I said, this battery gives about 50min of runtime for an Emerald/Obsidian saber.
The Xtar 14500 800mAh (Black) which is what the picture in the US Parts page is currently (described as "The battery has an acceptable performance, but it is possible to find better performing battery (That are slightly longer)."
It is .1mm longer than the Trustfire and has a discharge graph that looks like this:
My conclusion, unless you want to spend WAY more time than may be profitable trying to find THE perfect saber battery as a replacement for your Trustfire 14500s (adding in the probability that you'll have to modify or replace your battery sled... though I'm thinking about trying to find a HUGE rechargable Li-Ion battery for my stunts...) you might as well get the Trustfires (or Xtars) from US. Ten minutes of runtime for a six-to-nine-fold increase in price ($26 w/o shipping $36 w/... yes, for a single battery) is NOT worth it IMO.