Emergency Light Fixture

1. Why is there a separate charging cable?

2. Without a diagram of the fixture, there is no way to tell if the circuits have common elements.

3. Why would you assume that all emergency light fixtures are identical? How about providing the manufacturer and model number, the target application, the expected safety coverage conditions expected for its primary application, you know, that sort of detail. There is a lot that we can't see from here, if I may quote a respected contributor...

In my experience, those lighting fixtures which are designed as emergency lighting contain their own back up battery or super capacitor with a regulation guaranteed operating time once mains power is removed.

These are set up in the same way as a standard fitment with a single power cable.

Why make life more complicated than it needs to be?

Agree fully with your sentiments as all the emergency light fittings I have ever maintained have a single supply, unswitched by normal means, but isolated in a distribution board with a marked circuit. The fittings have either an internal SLA battery or a NiMH battery.

Let's not reinvent the wheel.

We wire in the emergency light as it comes from the manufacturer. It already has all of the required components including the battery.

This goes for both the passive and active lamp types.

Are you attempting to turn an existing light fixture into an emergency light?

If so, it's cheaper, more efficient and safer to buy and install a prepared emergency light.