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black_krix_si said:
the voltage regulator uses the battery as a reference point. dead battery and it will bump up to charge, full battery it puts out enough to maintain.
thats why taking out the the battery while running a car is a bad idea. no reference point and it charges high. and with no battery for the juice to go to it goes to your electral system until it finds a weak link.
ive never had a problem popping the clutch but ive never had a completely discharged battery in my car either.
As icarusdown said, If your battery is completely drained or disconnected, the car won't start. You may think the alternator will power the electronics once you get the engine spinning, but it actually won't. Why? Electrical generators rely on magnetisim to create current flow, but the alternator doesn't have any permanent magnets in it... only electromagnets. If you don't have any power to drive the field windings (the electromagnet), you won't get any power out of the alt when you spin it. On the other hand, once the alternator starts supplying power, current will circulate around and it will effectively run itself, which is why the engine doesn't stall when you disconnect the battery.
Anyway, a practical solution to the completely discharged battery problem would be to carry a second small 12v battery in the car - something with just enough power to run the electrics for a minute or two while you push the car.
You're right, the voltage regulator boosts output voltage to charge the battery, but it switches back and forth all the time - car electronics are designed to handle it. If the regulator were to boost the voltage so high that it could damage vehicle electrics, it would also eventually damage the battery (I've seen it happen with a bad regulator in a friend's VW). I think the reason you're not supposed to run without a battery has more to do with the alternator's available output. If you run a bunch of high drain accessories like the rear defroster, blower, headlights and such, the alt can't keep up so the battery takes up the slack. With no battery in the same situation, you end up basicly short-circuiting the alternator's output which could obviously damage it.
 
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