Ahh, but the were manufactured by somebody, any idea who and is the battery manual or automatic? There are lots of batteries and cartos available, some good, some not so good. Somkeless Image/Volt has what are arguably the best available.
There is a little "technique" to vaping versus smoking. When you inhale or draw on the e-cig do it like you are sucking on a straw rather than forcefully inhaling through it. It is possible, though not likely, that you are literally sucking the liquid out of the carto rather than getting it to vaporize properly in the carto. This effect can be amplified if the battery/carto combination are not really designed to work together, voltage of the battery versus electrical resistance of the carto, which can really add to having all kinds of problems.