Look for unprotected, safe chemistry 18650 IMR batteries rated 15C for maximum continuous discharge current. Always measure the resistance of coil(s) on an atty before installing them on a mod. For example, with a 1600 mAH AW IMR 18650 (15C x 1.6 AH), you'll be running it at one-third (or less) of that rating with a 0.5Ω coil (which is what two 1.0Ω coils in parallel are). I don't call that "stressing."