I believe the inferno is an Ego clone, with 510 threading, probably around 3.4V regulated. You should be able to use any 510 atty with it. I personally like original Joye 510 attys, 2.2-2.5 ohm, especially for tasting, since a bit higher resistance means cooler and more flavorful vapor. But any regular or LR atty should work. IKNVape LR 1.7 ohm attys are very nice too.
Even if you can't get your DOAs exchanged, you should contact the vendor and let them know. 2 out of 5 dead is not acceptable. But if you had another battery with 510 threading, I would check them on that battery to make sure they actually are dead, or check with a meter to see if the resistance is wildly fluctuating (open circuit, broken coil). They might not be dead, but just making contact with the center post of the atty. I've seen this with a few Joye attys over the years, but Joye attys are pretty much the standard of quality and longevity, and I've used perhaps 100 or more of those with virtually zero issues.
If they really are dead, at least make some noise to the vendor. They probably would want that info anyway, and they may honor the replacement or throw some other free stuff your way. Can't hurt!
