Modpack: Project Ozone 3 v3.0.40
Mod version: 0.3.13

This is actually a duplicate of #54, but I found out the specific value that is wrong.

According to my experiment in the modpack and Minecraft Wiki, the tank is using pre-1.8 values, that is:

• Before 15 level: each level has 17 xp;
• 16~30 level: each level has 3*level-28 xp;
• 31+ level: each level has 7*level-148 xp.

Starting from 1.8, the leveling values are:

• Before 15 level: each level has 2*level+7 xp;
• 16~30 level: each level has 5*level-38 xp;
• 31+ level: each level has 9*level-158 xp.

These values can be found in Minecraft Wiki:

• Current values are listed here under the table;
• Pre-1.8 values are at the bottom the article and folded.

This means that:

• When draining XP and the player is below level 11, draining gains XP.
  • This is what #54 is talking about: obtaining some low level then let the XP drain collect your level results in experience gain. Quoting there:

  If you place a XP Tap on a XP Drain Singularity Tank, turn it on and stand on top of the drain, you will receive more xp than the you are draining.

  • With other mods this can even be done with simple setup. For example, pipe the tank to an EnderIO Experience Obelisk, standing on the tank, open the GUI of obelisk, then repeatedly acquire 1 level every 0.8~1 second. You can see the stored XP in the obelisk steadily going up.
• As a consequence, below level 6 the XP bar actually sticks out to the right side during draining; but due to how minecraft render things, some portion of the xp bar to the right is masked off, so this is only visible below level 2.
• Conversely, when the player is above level 11, draining loses XP. Some reference numbers:
  • 315 xp is needed from level 0 to 15, but draining level 15 to 0 only gives 255 xp, about 20% loss;
  • 1395 xp is needed from level 0 to 30, but draining level 30 to 0 only gives 825 xp, about 40% loss;
  • If my calculation and excel formula is correct, the loss ratio after level 17 or so will never be less than 2/9 = 22%, and can be as high as ~41% loss around level 33.