My vape mod is at least 7 or 8 years old now and it doesn't seem to be functioning right anymore (like randomly shutting off when I didn't shut it off). I am considering replacing it with the Aegis Solo 3, (external battery only, NOT built-in). I will never buy a mod with a built-in battery. I can't find a straight forward answer anywhere about what battery is safe to use in it. All I find is "use a 18650" which I already know. I find nothing about the mAh. Can anyone tell me what mAh is safe to use in the Aegis Solo 3 external battery vape mod?