With the advent of modern high intensity white LEDs, making powerful, low consumption LED emergency lights have become very easy nowadays.
It's all about putting the LEDs in place by interconnecting them and connecting them to a battery. This battery is necessarily a chargeable one, so that the emergency light can be charged and used many number of times whenever required or during power failures.
To know more regading how to make a led emergency light, you may see the Circuit Diagram.
It basically consists of a group of LEDs white in color arranged in rows and columns and interconnected through soldering.
Atransistor is used to connect the positive of the battery to the LED array positive while the negative of the array is grounded or given the negative supply directly.
The transistor is rather
The transistor being PNP, stops conducting in response to a positive potential which is applied while the unit is plugged in to the AC input, the transformerless power supply associated with the unit starts charging the battery in the meantime.
However if the mains power fails now, the transistor switches the LEDs by connecting it back to the battery source, which hopefully was fully charged through mains AC in the course.