Need more info.
What strength cigarettes does he smoke and how many per day
What is the longest time is he away from power for charging each day
How willing would he be to use a stronger long-charge model that does not look like a cigarette
Does he have any technophobia or infirmities that would make it hard for him to fill his own cartridges with juice
Those answers will help others recommend which choice is better
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In general....
These are the most popular starters on this forum
100mah is enough charge for about 1 hour of moderate
vaping
Slim mini ecigs (a bit thicker than a cigarette, 100-128mm long)
Joye 510 or KR808D-1 short model (180-220mah)
Joye 510 mega xl (128mm long w/ carto) or KR808D-1 standard model (280-320mah) (120mm long w/ carto)
The most popular fat battery models (650mah and up, and able to optionally use the hotter low resistance atomizers and cartomizers that please vapers who want a stronger throat hit)
Ego or Riva 510 (best shop for these especially Riva 510 is Liberty-Flights.com and press the 20% off)
I recommend using all of them with cartomizers. There are prefilled cartomizers for KR808D-1 (which juice is added to so several days or more use can be gotten with each). The 510 models mostly have blank cartomizers and ship with atomizer+cart which is another way of
vaping (general cartomizers provide a more consistent experience)
I do not recommend a Ego-T or 510-T tank version for someone who is not going to get on this forum himself to solve problem - many people have issue with tanks
Stores for JOYE 510 manual are LiteCigUSA.net, Liberty-Flights.com (but you would have to look elsewhere for a the 280mah Joye mega xl kits)
Store for KR808D-1 manuals: Vapor4Life, SmokelessImage, maybe Bloogplanet (if they now have manuals)
Ego or Riva 510 as well as Boge cartomizers: Liberty-Flights.com
And these all need eliquid unless somebody is made of money in which case they could just use prefilled cartomizers and throw 1, 2 or more away every day.