Sorry, I was being snarky about Yihi and their chips.
If you're vaping a .5 coil at 35w, you should NOT be going thru 6 batteries even if you're chain vaping. You would have to take a puff (5sec) every min for 18hrs with no break to get thru 6 2500mah batteries. Even at half capacity that's 9hrs taking a 5 sec puff every min w/o a break.
Since you're only vaping a .5Ω coil at 35w, you really should look into a DNA40. I would guess you'd be down to 2 batteries a day, maybe 3. I just started using my DNA200 last night but with my DNA40's, I can get thru a day with 1 battery vaping a .11Ω NI200 coil at 20w with temp set to 430°F. That's if I'm just sitting at my desk most of the day (chain vaping at my desk). The DNA40 can go down to 3.2v w/o a noticeable difference in vape and can go lower with decreasing power, kinda like limp mode.
My battery was at 38% or 11.4v when I installed it. I fully charged it and I was down to 70% in a couple of hours. Then I realized that I didn't have the battery capacity set properly in Escribe (home built mod). It was set to the default 8Wh when it should've been 14.43Wh for a 1300mah 3S lipo. I've been vaping with a .11Ω Ni200 at 20w, 440°F and I'm seeing 87%, 12.3v (was fully charged this morning).Of coarse there's two ways this can be and one of them is to use my Opus very little but that is not the case here. Since getting my Opus it has never had the battery below 12.1 volts.
Which ultimately means I have no idea how well the battery in it compares to a DNA 40 with a single 18650 used at the same wattage but if I were to guess I'd say about the same.