  In this paper, we recall our renormalized quantum Q-system associated with
representations of the Lie algebra $A_r$, and show that it can be viewed as a
quotient of the quantum current algebra $U_q({\mathfrak n}[u,u^{-1}])\subset
U_q(\widehat{\mathfrak sl}_2)$ in the Drinfeld presentation. Moreover, we find
the interpretation of the conserved quantities in terms of Cartan currents at
level 0, and the rest of the current algebra, in a non-standard polarization in
terms of generators in the quantum cluster algebra.
