I had assumed that the V4L "OMG" was a rebranded smoktek Woo, but I may be incorrect about this.
To borrow some info from a friend who did a tech review (I am pasting it rather than linking, as it is on the vendor's website, out of respect to both you and the vendor):
"...It uses 2 rcr123 stacked with a step down switch. These batts came off at 3.61v hot off the charger. This shouldn't surprise anyone, 3.7v batts come off 4.2v as we all know. 3.7v is the maximum off load voltage these batts are rated for, so 3.61v is still in the safe range...."
"...Off load voltage on this device with 2 freshly charged batts was 6.88v. That's not a typo. Once load was applied things changed, the step down kicked in. For those who keep saying it hits better than the pt, well there's a reason why-
Load with cool cart at 3.3ohms- 5.36v
Load with wow carto at 2.3ohms- 5.32
Load with dual coil carto with tank at 1.5ohm- 5.22v..."
I used it with the smoktek dual and single coil tanks from 1.5ohm to 3.0ohm, though later switched to only 2.5ohm and 3.0ohm for battery life and concerns with stacked batteries. I was able to get 4-6 hours out of them with my frequent chain vaping. I would often swap out after 4 hours to avoid draining the batteries down too low, though. I could see how more moderate vapers could get at least 50% more than that...
To borrow some info from a friend who did a tech review (I am pasting it rather than linking, as it is on the vendor's website, out of respect to both you and the vendor):
"...It uses 2 rcr123 stacked with a step down switch. These batts came off at 3.61v hot off the charger. This shouldn't surprise anyone, 3.7v batts come off 4.2v as we all know. 3.7v is the maximum off load voltage these batts are rated for, so 3.61v is still in the safe range...."
"...Off load voltage on this device with 2 freshly charged batts was 6.88v. That's not a typo. Once load was applied things changed, the step down kicked in. For those who keep saying it hits better than the pt, well there's a reason why-
Load with cool cart at 3.3ohms- 5.36v
Load with wow carto at 2.3ohms- 5.32
Load with dual coil carto with tank at 1.5ohm- 5.22v..."
I used it with the smoktek dual and single coil tanks from 1.5ohm to 3.0ohm, though later switched to only 2.5ohm and 3.0ohm for battery life and concerns with stacked batteries. I was able to get 4-6 hours out of them with my frequent chain vaping. I would often swap out after 4 hours to avoid draining the batteries down too low, though. I could see how more moderate vapers could get at least 50% more than that...