How to make a charging-starting device for a car?

Good afternoon, it’s very hard to see from here what kind of transformer you have! But the simplest recipe is standard: we take the diode bridge to the required current, hang it on the radiator and connect it to the secondary of the transformer, add a regulator on the symmistors to the primary winding (a circuit like a dimmer for lighting) or any other regulator. All that remains is the question - will your transformer withstand the inrush current of the starter, will the diodes that you use withstand, etc. And if you just use it to charge the battery, then you need the output current to be at least 8-10 amperes.