Understanding when to use PWM vs DC-DC mode

[raccus]

I've been trying to do some research in regards to PWM and DC-DC mode for certain box mods. I understand that DC-DC delivers the battery voltage as a minimum and cannot "step-down" volts. Example, at a full charge, in DC-DC mode, I can only push 4.2++. In contrary, PWM mode can go below battery voltage and will kick on DC-DC mode once the required volts meets the battery minimum. This allows me to run at lower watts/volts when it calls for it.

With that said, I need help understanding the best mode for different coils/tanks. For this example, I am using 30W box mod that has PWM and DC-DC capabilities. I do not have the tanks to test so I'm basing these assumptions strictly on the information i've gathered. With that said, Is it safe to assume the following, given that the box is operating on a full battery?

Subtank mini with .5 coil @ ~25W/3.8V = PWM mode
Reasoning: The coil can run anywhere between 15-30Watts. Despite what's shown on-screen, in DC-DC mode, it will be pushing ~4.2 volts @ ~35watts. This will be too hot for the coil. Therefore, we have to "step-down" the volts to reach our desired wattage.

Subtank mini with 1.2 coil @ ~15W/~4.24V = DC-DC mode
Reasoning: Due to the higher resistance, it will be pulling >4.2v from the battery. Since it wont go below the battery minimum voltage, DC-DC would be best bet.

Arctic tank with dual coil .5 @ 30W/4.2V= DC-DC mode
Reasoning: The dual coils gives this tank the ability to run at higher watts. (minimum 30W). Because of that, DC-DC mode is best.​

 

[Thrasher]

best case scenario dc to dc is basically side stepping the electronics and hoing into mech mode.

With that in mind it will shine best with some subohm rebuildables like a dripper for example.

There is no reason you cant try it with those tanks umm off the top of my head I think .5ohms at 4v is around 30 watts

 

[raccus]

best case scenario dc to dc is basically side stepping the electronics and hoing into mech mode.

With that in mind it will shine best with some subohm rebuildables like a dripper for example.

There is no reason you cant try it with those tanks umm off the top of my head I think .5ohms at 4v is around 30 watts

This may be a dumb question but are there any risks running in DC-DC during a low battery?

 

[Thrasher]

Good question.

As I dont know the mod I dont know. I would assume it has low voltage cutoff no matter what mode its in.

But I dont think the mod will sidestep the safety features so it should be fine

 

[raccus]

Good question.

As I dont know the mod I dont know. I would assume it has low voltage cutoff no matter what mode its in.

But I dont think the mod will sidestep the safety features so it should be fine

Sorry, I should have been more specific. I am using a Sigelei mini 30W.

EDIT: I verified that this box does include low voltage cut-off. I appreciate your help