Word of caution: Do NOT forget the warning on the side of the nicads. While
I've yet to see one explode from heat, I've felt a couple get pretty damned
hot - while working with them. I guess it depends on their internal state.
And that was when trying to put solder on the ones that seemed to resist
taking it. IF the battery is going to take the solder at all, it should flow
on to it, like it would onto a piece of wire or a component lead and
likewise - be a quick hit with the iron. So, be careful with the heat... if
too much of it doesn't make the cell burst, it can fry it to render it
useless.
It's not impossible to do, but there are precautions.

As to nicads getting hot and bursting otherwise, I've seen it happen. I know
a guy who had a few spares in his pocket for an HT at a hamfest. He was
walking around, felt his trousers getting hot, then smelled smoke. They
caught his trousers on fire. He had some keys or change in his pocket and
well you know the rest of the story!
MNS.