The correct equation is

H = - 1 2 g é ê ê ê ë D V -   æ  ú Ö 2H g   ù ú ú ú û 2   + eg   æ  ú Ö 2H g   é ê ê ê ë D V -   æ  ú Ö 2H g   ù ú ú ú û < T

The parts in the brackets and the power of g are obtained by dimensional analysis (the coefficient of restitution, being a ratio of velocities, is dimensionless)

The overall signs are obtained by noting that the first part of the motion is down and the second up.