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Thanks pug100... and for pointing out my blunder about NiCad.
I wasn't aware of the ones used in computers, but then I don't have one, so I don't really know about what goes on inside them!
And Fitzer, I'm grateful to you for the tip. I shall have a look at their site at some stage, and hopefully save something on the high prices my local shops charge for one or two.
Shame they can't be recharged, though. I always hate throwing them away - I understand it's not entirely environmentally friendly.