20 watts fluorescent emergency light is constructed with few simple components and 12 volt 7Ah battery.
Circuit diagram for tube light emergency light
Construction and Working
In this circuit (12-0-12V) step down transformer is utilized as the fluorescent driver transformer that is the primary winding terminal is connected to the 20 watts fluorescent light and secondary (12-0-12V) center tapped terminals are connected with switching pulse circuit.
Here VR1 variable resistor and C1 capacitor is responsible for switching pulse that is applied to the switching power transistor Q1, 2N6101.(search in google to identify the pinout) This transistor connects and disconnects secondary winding of transformer with battery supply hence it produce EMF on winding this emf increases in primary winding (step up) and the supply is enough to drive the 20 watts fluorescent light.