I buy the prefilled Njoy tanks I have had no problems with them but one time a tank came that was leaking I wiped it off and connected it to the battery it did a bunch of bubbling then it was clogged when puffing a few times. I tossed the tank and got a different one. That one too didn’t work in the battery but worked in the other battery I have. So I suggest to throw the leaking tank away. It is better to trash $6 tank then a $30 battery! All in all one leaking tank from all I’ve bought is not bad. Just remember throwing a tank away is way better than losing a battery.