Smaller/higher wattage coil and you don't. I have a single battery Pico I've been running mine on for 2 days now (gone through about 4 tanks of the smaller Diablo). Keep the amp pull down and the battery lasts longer, but you can still get good flavor/vapor production with the right type of coil.
You can build for a higher resistance to save on batteries. Use steam engine and try to find the highest amount of heat flux while staying above .3 ohms. I would suggest you try 8 wraps of 26g Kanthal/2.5mm ID
I go through 4 or 5 tanks a day on the 5ml tank so I use it constantly but the batterie burns up twice as fast as with my other single coil tank. I really like this tank I just need a bigger batterie capacity so I can chain vape.
Anyways, what you could try, and I've been thinking about trying for a while. A nice higher ID coil crossed through the middle of the velocity deck with leads twisting around into the posts. Then take a thicker piece of cotton to wick, split it where it comes out of the coil and tuck those in the respective wells so you have each side of the wick filling two holes. Like I said I haven't tried it but it should work in theory with enough cotton.