It really does come down to what wattage do you have the IPow2 set at. It's a nice little battery, but 15W is a lot of wattage when you are talking about a Kanger coil (Nautilus would be a nice atty to go on that battery at 15W, though). The adjuster dial is at the bottom of the battery, give it a twist and see what your wattage is set at. In my experience, Kanger coils tend to be OK in the 9W range. If you've been hitting your coils, particularly when dry, with 15W, then you'll pretty much instantly scorch your wick.
If your wattage is set to a reasonable value, the next step is to monitor the coil resistance while you hit the fire button (the resistance is right above the wattage reading). If you have, say, a 1.8 ohm coil installed, the resistance should read approximately 1.7-1.9 ohms, for example. If the resistance is too high or jumping, you probably have a bad connection, which is causing the battery to throw more voltage to make up the read error. Try cleaning the battery terminal, threads inside the connections (battery, atty, and coil), and atty terminal. Reconnect everything and check the results.
If your resistance reading is accurate and you are not overpowering your coils, the final step would be to check actual output voltage. You will need an inline volt meter (some shops will carry these and/or have them available to help troubleshoot your issues) for this step. Connect the battery and atty to the voltmeter and give it a fire. You will need to calculate your target voltage from the voltage/resistance setting, compare that to what is actually being output.
If everything is checking out fine, and you are running low wattage, I am absolutely out of ideas...