On champions without mana, Manaflow Band is exchanged with Nullifying Orb.
It takes a minimum of 150 seconds to fully charge Manaflow Band.
Usually, an increase of maximum stat also leads to an increase of current stat. Since Manaflow Band is specially cased to not follow that rule, it will first shortly deduct the amount, and then increase the maximum mana. This effect is considered mana expenditure, for effects like Manamune or Eternity.
If the deduction in mana leads to a negative amount, Manaflow Band will actually increase current mana, since the stat is capped at 0. The deduction will effectively be lower than the successive increase of maximum mana which will then increase current mana.
New Effect: Hitting an enemy champion with an ability permanently increases your maximum mana by 25, up to 250 mana (15 second cooldown). After reaching 250 bonus mana, permanently restore 1% of your missing mana every 5 seconds.
Removed Effect: Your next ability with a mana or energy cost has its mana or energy cost refunded, and restores 8% of your missing mana or 8% of your missing energy.