It's not the battery you should be wondering about. It's the wattage of your APV device. If you use that 20W istick with the new Plus, you should be fine. I currently have it sitting on a sigelei 150W using the RBA section. My coil reads at .9 ohms..... and I have it set to 17W.
The OCC's that come with it vary. It says on the side about the wattage range. If I remember right, the .5 OCC is good to 30W according to Kanger. Others may pump it higher. Get a dry hit, turn the wattage down.
This is just WRONG, BAD ADVICE. A 20w iStick is not suitable to use with this tank. It can't operate with the .5 coils and even with the 1.2 coils it will burn them out much sooner than a properly regulated power source.
Even the 30w goes through 1.2 ohm OCC coils faster than any other device we have here. Burns them out sooner. (as tested against Cloupor mini, IPV mini and others)
It's time people admitted the iStick isn't the best thing since sliced bread. MOST of the problems people post about in this forum are directly related to using an iStick with their tank. Please get yourself a good quality device and you will enjoy your vape with your new tank so much more.