Methinks you might be misunderstanding how a passthrough works. The USB supply only acts to keep the battery charged. (A passthrough with a completely drained battery won't work at all until the battery gets at least some charge in it above it's cutoff level.) Since the passthrough is only there to keep the battery charged, you will never draw more amps off it than the battery in the passthrough can provide. If it's an 1100 mAh passthrough connecting it to a 4 Amp DC adapter will only produce... 1100 mA at best. Can't get out of it more than the internal battery will provide, no matter what DC power source you connect it to.
im sorry, but thats not the type of "passthrough" im talking about. the "passthrough" you are describing isnt actually a passthrough at all. youre talking about a battery that charges with a USB cable, and allows you to vape as you charge. lots of vendors call these passthroughs, but they are not.
a true passthrough is a device that works solely on power from the cable. the cable is not removable, and the unit has no internal battery. here is an example:
Variable Voltage EgO/510 USB Passthrough
what happens with this unit, is the amperage is governed by the adapter you use. the specs on the adapter become your vaping specs. most adapters are 500mAh or 1000mAh (1amp). there are other adapters that are 2amp, 2.1 amp, and higher.
using ohms law, its extremely easy to go over 2.1amps here:
Ohm's Law Calculator
plug in 2.1 under Current. then plug in 4.8 under Voltage. the result is the inability to use any atomizer under approx 2.3 ohms, and still receive its full potential.
steved5600, thank you for your input. however, going over 2.1 amps is almost a necessity. most mods are made with a much higher amperage limit. heck, even the twist is a 2.5 or maybe a 3, i forget. also, the linked passthru is the one i have.