Amp rating on alternator?

[BmoreBasshead]

I have a 93 Ranger XLT extended cab that I'm using for a project truck. It has stock alternator in it read it at 95 amps. I replaced it with a 2005 Ranger stock alternator that is rated at 130 amps is that a big enough increase for a car audio system? And also is it a big enough increase to add a second battery?

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[HardofWhoring]

for an amplifier, you take wattage/ amp efficiency, (80% is a fair number to use, but you can usually find yours to be accurate). Then divide that by voltage = amperage draw.
If it's a 1,000w amp,
1000/.8 = 1250.
1250w / 14.4v = 86.8 amps. (the slightly overage estimate is 9 or 10 amps for every 100watts).

Your stock alternator is sized so that if you have everything going you have enough. Your EFI, lights, AC, horn, turns, cig lighter you are probably around 80amps.

If you have a 1,000w sub amp, it's only full draw on heavy bass notes. Between those bass notes it's using less than your alternator is charging. If you listen to heavy bass music like rap, it's going to draw more often. There's a few factors that you need to consider. Maybe it's a winter beater and you don't use AC. Maybe you buy a really efficient amp, or a really cheap one. My guess is somewhere between a 500-800w total setup would work with that alt, and not cause problems.

A second battery is just a storage bank. If you put in a 2K watt system, with that alt, you're just going to kill two batteries, it will just take a little longer.

Not sure what your plan was, but I think that alt would work with a system that's a single 500w amp, with a 500w sub, and something around 80-100w per ch on a second amp for door speakers, maybe a 4ch amp.

 

[metalheadjoe 10+ year member]

Yes that's better than most people power their stereo with. I have a 130a in my 4.0 b2 and it does great.

 

[some dude]

My car had 100 amp stock alternator. I upgraded to a 150 alt from a newer car.
I run 1 80AH AGM battery and a 3,000 watt amp.

I use my stereo every day and my battery stays topped off.

Now I'm not pulling 3,000 watts ever but I turn it up periodically and I can jam hard and my electrical is totally happy.

 

[spokey9]

The stock alt on my saturn was 90 amps...I ran a 800w monoblock with no issues (although playing music probably rarely pushed the 800w )...the doors were ran off the hu...