If you love your cartomizer and do not believe that they cannot be refilled and you do not wish to make the switch to an atomizer which is a bit easier to refill just keep reading. Most electronic cigarettes with cartomizers are sold and advertised as disposable, however, they can be refilled but it does take some effort. Some people actually refill the cartomizer ten times before tossing them and buying new ones.
There may be another way to refill your cartomizer, however, this is the most common and easiest way to ensure you actually get the e-liquid in the proper place and do not cause any damage.
Remove the battery from the cartomizer. It is never a good idea to refill your cartomizer or even your atomizer while the battery is in place. You always take a chance of getting e-liquid in the battery which will completely ruin the battery. If you plan to use a different flavor from what you used previously or different from the pre-filled cartomizer, then you should clean the cartomizer prior to refilling. If not you are not going to enjoy the flavor you will receive and you not enjoy the experience at all. You will honestly ruin your cartomizer if you mix flavors.
The Refill Method
You have to remove the plastic end of the cartomizer. This is best accomplished using a sharp item like a thumb tack, paper clip or other item that can fit into the hole and allow you to pull it off. Some cartomizers tops will come off very easy; however, a few manufacturers have glued these ends on just a bit to discourage users from refilling. It may take a bit but it will come off. If you do break the top, then of course you will have to throw it away or you can add another cap from a different cartomizer or even get an atomizer that will fit on the end. Once you have the plastic end off, look and see if there is a small rubber ring over the top of the filler material. Some companies add this as well to ensure the e-liquid stays in place. If there is a ring, it will also need to be removed.
Now, that you have everything removed, you should be able to see the filling material. Take a look and check out the filling material. You do not want to refill if you see any dark spots as this is burned and will not provide a nice flavor when vaping.
Hold your cartomizer at a bit of an angle and slowly drop the e-liquid into the hole. Do not let the drops go into the hole in the center of the filling material. It is best to let the drops slowly slide down onto the filling material. Rotate the cartomizer and slowly drop in the juice until the filling becomes saturated. If you overfill, use a paper towel to absorb any extra. Replace the rubber ring and the plastic end. Wait a few minutes to allow the wick to absorb the e-liquid and then screw in the battery.