Driving a DART with an Ultra? IMO this is the one you want:
http://www.lighthound.com/AW-IMR-14500-LiMN-Rechargeable-Lithium-Battery_p_3644.html
It's what came with mine, it's the flat out winner at delivering maximum power.
OF
A little late to reply, but I wanted to agree with you 100% about the AWIMR14500. It may be the single only lithium battery I've found in years that actually provides more than the capacity it advertises. I just ordered one of the Alpha Ultras w/DART core that TET is selling from (dwindling) existing stock the other day. Though I love my UltraLite, the 10440 batteries just don't have enough capacity to be any fun. (Turns out to be too much like work dealing with a bag of batteries and subsequent recharging; I knew this going in, but the tiny size of the UltraLite fogged my brain).
Anyway, I had three brand new AW IMR14500s that Zeki sent me by mistake a month or so ago, that I hadn't gotten around to sending him back, (I actually wanted some more 10440s, not 14500s). When I ordered the Ultra, I took the unused 14500s back out of the mailer (see, sometimes procrastinating pays off), and ran them through a couple of charge/discharge cycles in anticipation of the Ultra arriving, and they are really outstanding cells!
You can safely charge them at up to 1.5A (that's 2.5C, 25 minutes from dead to full), and you can continuously discharge them safely up to 4.8A (that's 8C). They're LiMN chemistry, so no protection circuit is needed. I discharged them at a constant 1A (1.67C), and two of my cells provided more than the rated 600mAh (620 and 633) with the third providing 599mAh. Cell manufacturers typically rate the capacity of their cells at a 0.1C discharge rate, not at the higher discharge rates that we use, so I would expect a significantly lower actual capacity, not a greater one. The Tenergy RCR123A batteries barely provide 400mAh at a 1A discharge rate, and they're manufacturer rated at 750mAh. The IMR10440s are rated 350mAh, actual @ 1A discharge is 200mAh.
So these are really outstanding cells!
I also wanted to mention that the Alpha Ultra is MUCH smaller than the Cera. I want a mini Cera too, but since it's gonna be a year (if ever) before a mini Cera is born... The Ultra easily passes for an e-cig. It works well in combination with a Revo/DART head. It ain't gonna be around very much longer, and TET is selling the last stock for a song. The custom made aluminum case originally cost more than the whole kit costs now. If you've been vacillating about buying one, now is the time. (In fact, they may be out of battery chargers already, though that's an easy item to pick up elsewhere if TET is out of stock). Just a thought.