Most popular first ecigs here, from very short battery life to very long
And I am talking about MANUAL batteries for all of these. Most people here use and recommend manual batteries - less easily damaged or killed by juices leaks, will not turn on accidentally from wind or vibration, more control of your hit
100mah is about an hour of moderate vaping
Joye 510 w/ manual batteries (I use w/ blank cartomizers) - 180mah (Cignot.com, PCC at NoSmokeVA.com)
Joye 510 w/ manual mega xl batteries (I also use w/ cartos) - 280mah but long (128mm w/ carto) (FreedomSmokeUSA.com, only a less roomy metal PCC available)
KR808D-1 w/ standard manual batteries (prefilled or blank cartos) - 280mah and 120mm long 2/ carto (LiteCiguSA.net, Vapor4Life.com, PCC is a non-roomy flat metal pack)
Then the fat battery models - very popular
Ego or Riva 510 w/ 650mah-1300mah batteries and can optionally use hotter power-hungry low resistance attys & cartos
I use both 510 manuals and KR808D-1 manual, have full charging setup at work, NoSmokeVA PCC for the 510 and for holding both 510 and KR8 cartomizers. And I carry a charged Riva 510 battery with me.
Re prefilled - only a tiny convenience since EVERYTHING need eliquid (unless you are a millionaire and want to throw away prefilled cartos every day), Prefilled is not even a convenience if you don't like what is in the cart or carto.
In general I recommend
KNOWN POPULAR MODEL NUMBERS
MANUAL BATTERIES