A single 4C rate charge is probably not going to harm the battery pack enough to measure IF you don't overcharge. A good peak detecting charger will prevent the overcharge. (I bet you used one too. )

If the NiCd is manufactured for high rate charge/discharge, such as the RC car 7.2 volt power packs... then it will do fine at 4C rate for its expected life. These type cells typically don't last as many cycles as the type cells used in a TX or RX pack. So... the type of battery we are talking about matters.

That Hobbico charger should have an LED for the TX and one for the RX. When the LED is glowing bright... it is quick-charging. When it is flashing it is on the trickle rate for the settings. If it is off, nothing is happening.

***********

NEVER quick charge a hot battery and if it gets hot... get it off the charger. Hot battery plus fast charge = boom.