2.0 A rate is essentially 4C for a 600 mah pack... that is the extra-fast rate we have been saying to AVOID!
In a case of emergency recharge... then the 2.0 A rate would be a 20 min charge.... generally there is no emergency that warrants doing it. These things are not providing life-support for someone.
For RX ot TX packs rated 600 mah... you want to avoid charging at over 0.6 A rate. If you have a choice of 500 ma rate or 1.0 A rate... then go with 500 ma.
Sit back... yack with the other guys at the field... and wait an hour or two for the batteries to charge at 600 ma or 300 ma charge rate.... If you ever fly enough in one session to actually need to fast charge...