Caution with fast chargers... you can cause NiCds to explode if they get too hot. The NiCds n a TX are not designed to handle the 15 min charge rate. A 1 hr rate is safer. (and don't neglect to get the peak detecting charger that turns itself off. Timer/resistor chargers destroy batteries.)

One time letting the NiCds go flat like that... probably not a big problem. But do it a few times and you can ruin the battery. NiCds don't like being drained below 1.1 v per cell.

Another note about fast chargers... remove the battery from the TX while charging. It alows better airflow around the battery keeping it cooler. It avoids any diode in the TX without doing a TX modification. (peak detect and a diode in the charge circuit = no peak detect!)