@Colin_Camper
Well, Ni-cads actually don't do so well in constantly charged scenarios. Unlike lead-acid they do better if they are fully cycled (last about 1000-2000 cycles) or if they are being stored, fully discharged.
I Agree, perhaps were one to store some Amiga MB's they should discharge the batteries with a 1 ohm or so wire beforehand. I am not sure though if a Ni-Cad would "come back to life" if stored with a dead short. (probably not, but beats the alternative?)
Having said this I paid Analogic £100 last year to replace my A4K battery!
A little steep, perhaps, but its a risky custom "operation". I would charge at least $75! 8-)