How many watts can I run off a 85amp alt?

Question

Wondering how many watts I should run off a 85 alternator with the big 3 upgraded.

Answer 1

ok so you have a stock alternator (85 amps)

assuming it does a decent charge at 13 volts

power= volts * current = 13 * 85 = 1105 watts

out of those 1105 watts , some of that goes to recharging your battery, vehicle computer and accesories AC, headlights etc. out of the left over lets say you are left with 500 watts

500 watts will be used for your amp, that most likely will not be 100 % efficent , so my friend you can cound if you are very very lucky with some 300 true watts rms from a decent amp.

300 watts rms that's all you can run, if not less because remember 85 amps from your alternator when new, if it is old already, you will get a lil less.

I know this are not good news but hey, it is what it is.

dont be fool by people with big amplifiers, you only have what your alternator gives you. stock 85 amp = 300 or less true rms

Answer 2

WOW! Not even close.

The formula is as follows:

volts X (alternator output X 0.4)/(amp efficiency)/0.667

Which comes to 880 watts RMS assuming an amp with 80% efficiency.

Broken down that's Volts times 40% of the alternator divided by amplifier efficiency divided by the average musical signal power in a test tone.

I'm running 400 watts RMS from a 75 amp alternator with no problems and it's a Class A/B amp.

Answer 3

Power (watt) = V (volt) x I (amp)

So 12 x 85 = 1020 watts.

that includes everything (headlights, blower motor, radiator fan, etc.).

Good luck...