I’m building a triple s2. This will be my first multi-emitter build. The emitters are wired in parallel. Curious to know what’s the max amps that I can throw at it? I’m guessing at least 9amps?
If you are using a battery you dont need to worry about it (for XP-L HI in particular). The voltage will climb too high before the emitter is in any danger. You might be able to pull 12 or 15 amps for a few seconds with a really high quality battery and it will be fine.
I would settle for an 9-12A driver. Of course due to heat, max output will be available for just a few seconds, but that’s expected when you build a hotrod 
9A (3A per) on a DTP board is well within the tested limits of the emitter. Cree rate them for 3A, but they use non DTP boards and are probably conservative for maximum lifespan even then.
XP-Ls (HI or otherwise) have a sweet spot around 6A for absolute maximum output, so you could theoretically drive a triple at 18A. However, the proximity of the multiple emitters, along with what is likely a small host would make it risky.
This can all be ignored because with a high drain cell you won’t reach the voltage required to pull 18A (4.1V over LEDs) because of the cell sag, and voltage drop over the driver. Realistically you’d be looking at 10-12A on a full cell from a low resistance triple. That will give you plenty of brightness, and be well within their safezone.
this is really good info guys, highly appreciated and definitely will be taken into consideration for my triple build!
Triple S2? That’s a 1x18650 light.
XPL or XPL HI triple should safely take any amount of amps those cells can provide. FET direct drive should work just fine.
However, be advised that the head of your light will get hot FAST. I suggest using a driver with a temp sensor built in like the H17F to avoid burning yourself on the hot head.