Although it was found in a British magazine 1976, this circuit can be easily upgraded with the replacement of transistors. Thus, for BC108 or BC109 or BC548 we can use BC549 and for the BFY50 can use TIP31. The batteries B1, B2 and B3 can be NiCad batteries. A possible amendment of R1 may be necessary to obtain the correct load current. The transformer is 6 + 6 V at a current of 250 mA or more. It primary winding must be according to the power grid. The array of transistor terminals in the drawing is for the BC108 / 109. The lamps may eventually be replaced by types 3.5 to 4.5 V (flashlight) with currents ranging from 100 mA to 300 mA, always remembering that the total current of the set of lamps shall not exceed 1 A.
