I think the original question was about charging the battery using the built in Micro USB charger. I could be wrong.
That was what my replies were based on. 2 amp charge for an 18650 should be ok in an external charger. If they do not get too hot it is fine.
Many new mods use over 1 amp of input current thru their internal charging circuit. If you only use a 1 amp USB adapter for those problems can arise. Cooked adapter or cooked charging circuit in the
device. Also be sure that you re using a heavy duty USB cable. One for a cell phone may not be adequate for a mod.
Also if the mod needs 1 amp for charging thru the micro USB port and you only use a 1 amp adapter then it will not last and could potentially damage the mod charging circuit when it fails. Not a good idea to run anything at 100% all the time.