so with this method, you've not had problems with the juice getting onto the battery?
When using auto batteries, after filling, no matter what I am filling, cart or carto, or how I am filling it, I insert the battery connection of the atty into the opening of a bottle and then blow through the mouthpiece until it stops making the bubbling sound.
I used to use one of the TW 5ml bottles with the opening reamed out to fit a cart/carto into but the 10ml juice and flavor concentrate bottles work perfectly without drilling or reaming them out.
I use a bottle because I a few drops here and a few there add up to quite a bit over time and I hate counting drops.
I will be getting a set of syringes with blunt tipped needles soon so that should help not having to count drops and also make adding the amount needed more accurate making the blow through into a bottle less necessary, although I'll likely still do it just because.