There is a chance, albeit slight, of nickel cells exploding if left to overcharge long enough at a high enough amperage.

I stand by what I said. If it's a wall wart that says on the casing OUTPUT: 7.2V, 1.2A, then it will be fine. Of course it will have to be monitored / timed especially at that charge rate.

If it's a charger designed for a 7.2v pack, then no, do not use it, because the output voltage is likely upwards of 8 or 9 volts.

If you have a cordless drill, take a look at the charger. For example, I have a 24V drill, the charger puts out 28V. My 14.4V craftsman
charger puts out 18V.