Automatic Emergency Torch

Good day,thanks for helping me.I got this circuit from the web in pdf format.It is explained in detail.The circuit originally ran off a 2.4v Ni cd battery.I would like to change it to atleast 6v.Could you please show me your calculations on how you would modify the circuit by changing any resistance or capacitance
Thanks a lot,really appreciate it.

I think all you need to do is change the battery to 6 volt and the bulb to 6 volt, 250 ma.. The battery should be able to stand the 70 ma trickle charge.

But wont this interfere with the switching of the transistor if i increase the battery?Surely the resistance connected to the transistor have to change.This circuit should only be activated if the ac mains fail.Could you explain more about your answer?

R4 adjusts the charging current. It should be 1/100 of C where C is the capacity in (mAh) of the battery. This if a Nicad is rated for 1000 mAh, then the continuous charging current should be less than 10 mA.

The transistor is PNP and thus turns on when the base is made more negative than the emitter by VBE.
Current in the base is limited by R3 and there must be enough current to cause saturation which depends on Hfe (current gain of the transistor) and the battery voltage.

Charger

The current is set by the reactance of the 2 parallel .47 Ufd. caps. (1/2pi f c), so you must tell us how much current you need to charge your 6 volt battery. I assumed it was at least as large as the 2.4 volt ones. If you use the same current the 35 ohm resistor just bypasses some current around the led to keep its current low enough. The 470 ohm resistor was a little small in the first place to get good saturation of the transistor so just leave it alone and the base drive will be about 11 ma (still a little low but ok.)
The stuff I read on Nicd says they can tricle charge at .05 to .06 C so if they are 2200mah batteries the current should be ok.