Hello Kai
Thanks.National Panasonic Ni-Cd P-50AA(known enemy ..) regularly charges for 15 hours for supposed to be 500 mAH @50mA (printed on the cells) by LM317 in constant current mode;regularly because of the infamous memory effect of Ni-Cd systems.But discharging these @100-200mA as assumed by me or @ 70mA assumed by you cannot be regularly done;I think C/20 i.e. @ 25mA is safe recommendation.I run a portable recharchargable battery backed(4 x P-50AA) 2051 reverse chess clock with 16x1 LCD with LED back light quite successfully till I forget their memory effect.But why we are discussing battery charging;Stanley in his original thread probably wanted to waste as little voltage as possible in stabilising his ever dwindling battery voltage feeding a huge load from his preffered kind of batteries and that to for a reasonably long time.This is height of design tension tempting me to say "you can't have the hen and eat it too".
Rudra