Yes you can refill the carts with the liquid flavored ejuice. You will want to change out the filling in the carts sometime. What I found out after starting to vape... You need more batteries, a pcc, extra atomizer, extra carts, cart filler and juice. I have ended up with 2 full 501 kits, a pcc, blue foam filler, car charger, extra carts and keep my juice handy in a bottle buddy. But I can't plug in a charger at my job so I have to have the pcc for work. It does sound expensive but I started vaping in Jan. After all the trial and error, not having the juice or supplies or whatever minor problems I have run into I'm no longer smoking analogs and have not for 14 days. Sometimes I have to work 16 hours straight so I will end up with 2 pccs. I have spent less than $150.00 total on all of this. So after a couple of months I will have actually saved money by not buying analogs. I no longer pre-fill the carts to use later. I was wasting juice that way so I keep them clean and ready to use if I want to change juice flavors.
I hope this helps you out.