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Hypothetically speaking, let's say I've equipped a vehicle with an aftermarket audio system with an amplifier that has a higher draw (in amps) than my alternator produces causing my average voltage (while system is active) to drop to around 10-11 volts. How drastically can I expect this to effect the life of my alternator and battery?

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up vote 1 down vote accepted

After installing high wattage stereos with stock alternators, I have burned out alternators in less than 30 minutes, and I have also had them last months. It would be prudent to plan for an early failure.

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If you put too much of a load on the alternator it will constantly max itself out as it tries to keep up with the demand. Running at max will heat up the alternator and eventually it will burn out. As @Brian pointed out, probably sooner than later.

Most aftermarket audio systems that require higher amps also have high output alternators.

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Better consider an alternator upgrade when it blows up. You'll probably be blowing it up pretty soon. :-)

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