Unless HK wired up a pack backwards or miscolored the wires it won't hurt it. As Davidka said, unless you are running perfect matched Nimh cells, the voltage "ripple" created by them will do far more damage than any lipo. All CC says last I looked is to not use packs rated for less than 75amps CONTINUOUS discharge.
The ESC can't handle surges in power going up and down drastically. Zippy packs don't do this and they've been tested over and over. Keep supporting companies that blindly rip you off like MaxAmps, Reedy, etc and let the rest of us enjoy $18 packs and $20 chargers that perform as well as or better than anything else on the market.
