1. Re difference - yes 510's and Egos all have 510 threading. HOWEVER low ohms cartomizers and atomizers (stuff below 2.5 ohm) are not for slim 510. Slim ecigs use standard resistance (like 2.5 to 3 ohms). Only big batteries 450mah+ in size should be using the hotter low ohms (aka LR, low resistance) stuff because the big batteries have beefier electronics to better handle the increased current used by low resistance attachments. Also - some people won't use as low as 1.5 ohms on Ego - some do and most don't have problems but it may damage the battery especially if the battery is a cheaply made clone Ego and not Joye or Janty.
Also - the -T models come with tank atomizers and tanks instead of normal atomizer + cartridges. The 510-T auto model's charging cable may fry other 510 batteries so only use a 510-T charging cable with 510-T auto batteries. If desired, a 510-T tank atty and tanks can be bought separate and put on any 510. An Ego-T atty (2 sizes) and appropriate size Ego-T tanks can be added to any Ego. Another note - never use Ego charging cable on slim 510 - too many mA and can damage the slim batteries.
2. You just don't know how to fill cartomizers.
Here's how I fill plain stuffing cartomizers. You'll need to know the ml capacity of your cartomizer. if you bought some kind of huge carto this type of filling may not be sufficient - some very deep cartos need a combination of methods (like syringe or carto condom method for bottom and dripping for top)
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How I fill Vapor4Life KR8 cartos and Boge 510 cartos
With the carto off the battery... Pop out the soft cap with an unbent paperclip in the mouth hole, very careful not to catch stuffing or the wire loop.
Shake and open the
eliquid
Fill
Hold a bit of tissue on the threaded end hole, tilt the carto, and add 18 drops per ml of capacity into the stuffing (Boges and most KR8 cartos are about 1ml).
Wait 15 seconds or so then see how many more drops the carto stuffing will soak in easily.
Cleanup
Clean up the threaded end, tilt open end down into tissue, puff into threaded end to clear air channel (Boges and the KR8 cartos I use have a defined center air channel and I want to see light through that) While the carto is still open end down, touch a soft bunch of tissue to the top of the stuffing to get the loose juice - this will help prevent leaks.
Settle (first fill only)
Cap and let it settle - I lay it on different sides for 15-20 minutes to make sure every bit of stuffing gets damp so I won't singe the carto. if you use thicker juice than me (I use 20% Vg or less) then you may need to wait much longer.
While
vaping
While
vaping, if the vapor gets a bit light or a bit dry or the carto is getting hotter than normal, I take the carto off the battery and add eliquid. Also, I use such light sediment-free juices, I can look at the stuffing and see if it needs juice because the stuffing goes back to near-white.
I often use a plastic or delrin drip tip as a mouthpiece on Boge and KR8 cartos (not to drip into since the juice would head for the central air channel). Easy to pop out to add juice.
and yes generally a 510 connection is a 510 connection
