5V or 6V could melt the cart. Even 3.2V will sometimes put little dents in the cart. Carts on HV are generally not recommended. But that said, the correct way to fill a cart which has stock fluval filler in it (like course cotton) is simply drip slowly onto the filler until it is juicy but not pooling on top, perhaps use a paperclip to work out air bubbles, and add drops again until it is juicy on top. Put a drop on the atty bridge to get wicking going, and enjoy...for about 5 hits before it starts to get burny. Unfortunately stack carts are far less than ideal for wicking
juice to the atty bridge, and so many many "cart mods" have been created to try to solve this. I've pretty much done them all, with the zero-filler mod being the "best" (still not great and high maintenance). I think I can speak for pretty much all vets when I say that we either drip or use cartomizers. In fact I most often use a carto with a drip tip...its the vape I like best...at least today it is.
Tank cart/atty systems are the current mass-produced version of the zero-filler mod, and I think people are using them at higher wattage, but I don't have this technology yet. I personally have not used an original stock cart in 18 months, at least. A 2.5 ohm Boge soft-tip carto on an eGo is really good to me. For you, I suggest trying some 3-3.4 ohm cartos on your 5V PV...its a great combo on my 5V passthrough. And I don't think your carts will hold up well with 5 or 6V unless you are using at least a 3.5 ohm atty. Everyone is different, but even a regular 2.4 ohm 510 atty on a 5V PT is a bit on the hot side for me, but if I do that, then I will definitely be dripping, not using a cart.
Good luck!
