First off, I wouldn't have an auto battery...too risky to kill with
juice.
Secondly, I don't care too much for pre-filleds plus they usually aren't filled completely full.
Thirdly, I would rather fill my own as it's cheaper and can keep topping off the cartomizer or cartridge.
And last but not least, I hate having to draw on an auto battery so hard. It makes my cheeks hurt after a bit. IMO, autos have too goofy of an airdraw. They are either too light or too tight. Manuals give you the power to control your
vape where an auto doesn't. Plus they have a nice even draw. If you like a tighter draw, put a small piece of take halfway around where the atomizer screws into the battery. For a lighter draw, back the atomizer off by 1/4 turn...just make sure you don't back it off too much or it won't fire.