O.K. Without know the application for use I could ask, "why not just use the 12V power supply run the light?" Can you explain what will be powered by the 9V battery you will have under charge?the goal is still the same and in both schematic i know i have used a light bulb but their is no light bulb that i want to lit. so i see where it can get confusing. ill try to be clearer with my schematic next time. so again i need to charge and use a 9v battery (400mAh) with a 12V (2.1/5.5mm) source. the x1 bulb in the "simple 9v charger picture" is the 9v battery.