Originally Posted by
Highend
I didnt read everything in your post haha yet..
Iam saying you can not run directly from the battery to a source DIRECT.. without anything.. I know my electronics yet iam not great at explaining it. Just as the same i can get to my house but cant give directions.. haha
The bettery is putting out 12v your alt is going to raise the output the battery will put out. so what you were asking of 12v prior your getting 13.8-14.2V... so if you know what your doing you can use the battery direct as a power source yet you need the proper resistance.
EDIT: do what you must. Yet i wouldnt run it directly.
No.
Resistance has nothing to do with any of this. If you raise the voltage on a light bulb, it will just get brighter.
The battery and the alternator are directly connected. Whatever voltage level the alternator is putting out is whatever voltage is going to the battery also, so everything connected to battery power is also connected to alternator power, and everything is at the same voltage. Your headlights are connected directly to the main power circuit in the car, which is directly connected to the alternator and directly connected to the battery. So when the engine is running, the headlights are getting voltage the alternator is putting out, and when the engine is not running (and therefore the alternator is not moving), the headlights are getting voltage at whatever voltage the battery is charged to. This is why your headlights are brighter with the engine running, and stuff like your window motors move slower with the engine off. If everything was connected to the battery only, nothing would change whether the engine was running or not, because everything would always have the same voltage (and the current is already set by something else; see below).
This is the same with a fuel pump, amplifier, fan, whatever load is connected to the main power circuit in the car is directly connected to both the alternator and the battery at all times.
I think the breakdown here is that you are thinking about loads which aren't current limited. Anything that has resistance (the windings of an electric motor, the filament of a light bulb, etc) already limits its own current, according to V=IR (voltage = current x resistance). So in the case of a light bulb, or a motor, the current it will draw is the voltage divided by the resistance. That is the max amount. One of those things has to change for the current to increase. Either the resistance has to somehow become lower, or the voltage has to get higher.