What exactly did you do here?
Can you explain with a bit more detail/description of which wires you were connecting? There are specific locations the charger wires are supposed to go. If not, you can damage the charger and or the car systems.
the converter DC/DC on my gem is dead so waiting for the replacement i put a 12V battery directly into the +12V switched and unswitched with the ignition switch pin plug on the +12V unswitched and - of the battery into the gnds pins.
This is also not a very good idea. Back feeding power into car electrical systems without knowing how everything works is a very good way to destroy hard to find and expensive components.
Instead of trying all sorts of wildcard tricks “just to get it to light up”, I highly recommend getting to know the car systems first, solve the issues that you know about, and power up the car properly.