My father-in-law has some solar powered lanterns, that charge up 600mah ni-cd rechargeables. He now needs some new ones, however he thinks they are special ones that can be charged very slowly (by the solar array). My question is, are these just normal ni-cd batteries, or are they special.

Wisdom of STW please dont fail me.

Many thanks

Panda

Special – I doubt it, unless you mean special as in really really cheap ones.
You don't need special batteries for slow charging. Though I think that I am right in saying that NiMh batteries would fare slightly better because they are less prone to crystaline growth, which is more pronounced at low charge rates. You probably can't get hold of NiCds anyway these days.

HTH