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Do I Need To Get A Larger Alternator For A 600 watt Stereo System

soundhd

soundhd

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In the process of adding a aftermarket stereo system to my 70 RR. The 5 channel amp has a max output of 600 watts. Will I need to change my stock alternator to a larger size?

Thanks
 
you might, what is the stock size-60 amp?
600 watts=50 amps at full blast of coarse.
I'd double check the wiring size as well or you might melt some of it...
 
Check you voltage at the battery when you have the volume at your normal and lights on so you know you can drive with out discharging the battery
then decide
 
I'll tell you that I'm no expert on stereos, but I have seen a lot of the "hip hop" guys with big systems using Optima batteries (sometimes two of them). Deep cycle marine batteries might be helpful too. I guess it depends on if you want to play your stereo in the park or just while driving. Also, I "think" I've seen some 100 amp alternators around somewhere.... either aftermarket or from newer Mopars (maybe late '70's Cordobas or something?)
 
The older high amp alternators are huge and require different wiring. If planing going serpentine on belts now would be the time. Smaller high output alternator can be found. Do not know what it would be like to adapt one to v belts.
 
First, what alternator are you running? Is the stereo installed? If so, pick up a clamp style ammeter and clamp it around the main amp power lead with it as loud as you can stand it. That watt rating of the amp is peak (as I'm sure you know), so who knows, you might not be as close to that peak as you think.

- - - Updated - - -

btw, if you knew a decent machine shop (heck, even a vocational school), you might be able to turn your alt pulley down a bit to get some more rpm out of it.
 
Thanks to all for the replies. The 600 watt "max" output on the amp is with a pair of subwoofers but that will not be for awhile....just going to be running 4 speakers in the cabin area for this summer...max would be 300 watts at the most. Do plan on adding a serpentine kit sometime next year....so hopefully I can by with the stock alternator till then...by the way how can I tell what the output is on the alternator? Assume there is a model or serial number that I can copy down and reference.....

thanks again
 
soundhd said:
by the way how can I tell what the output is on the alternator? Assume there is a model or serial number that I can copy down and reference.....

thanks again
Click to expand...

I would take it to a local alternator shop and have it tested because who knows if its performing as it should.

The other way would be to take that clamp-style ammeter and actually measure how much your alternator is charging. Just clamp it around the charging wire off the alternator - be sure that's the only wire that's in the clamp of course. Heck, if you wanted to geek out about it (like me), if you had an assistant, you could create a little charging curve over the entire rpm range. Keep in mind, though, that the alternator will only provide as much juice as it has to, so if you are drawing 10 amps, it will only give you 10 amps no matter what rpm you drive it to. So in a sense, this method really won't tell you its max output at a given rpm unless you are drawing so much current that you are maxing the alternator out.
 
a clamp on meter would need to have a direct current DC option as most I've seen are AC only and they can get a bit costly. My AC/DC clamp on was over $1200.
You could probably rig up an cluster ammeter in series to measure the amps but in both cases, the readings only indicate the load applied, so you'd have to crank the stereo up, along with other power loads.
To see how much your alternator is charging, a voltmeter will tell you. The volts will drop down to the battery level, say 12-13V, if you exceed the alternator's capacity when adding loads like your amplifier, headlights, blower, etc.
If the voltage reading stays up above 13.5V, with all of these loads on, your alternator should be fine.
However, the wire from the alternator, throughout your harness should be checked for size and monitor the heat of the wiring. Too small means added resistance and overheating, melting & fire.
Make sure all of your ground connections are clean of corrosion and rust as these areas are often overlooked, adding resistance to the circuits which can cause many issues.
 
Glenwood said:
a clamp on meter would need to have a direct current DC option as most I've seen are AC only and they can get a bit costly. My AC/DC clamp on was over $1200.
Click to expand...

True, most don't do DC through the clamp, though that must be a very sweet meter for $1200.
 
It is a Rockford R600X5; Speakers (4) will be 4 ohm speakers so will be running a 200 watt load this summer.
Rated Power
(RMS Continuous Power): 50 Watts x 4 +
200 Watts x 1 @ 4-Ohms

75 Watts x 4 +
300 Watts x 1 @ 2-Ohms

Photon440 said:
What's the make and model of the amp? And is the rating at 2 ohms?
Click to expand...

- - - Updated - - -

The car currently has an Optima Red top battery with both top and side posts.

PurpleBeeper said:
I'll tell you that I'm no expert on stereos, but I have seen a lot of the "hip hop" guys with big systems using Optima batteries (sometimes two of them). Deep cycle marine batteries might be helpful too. I guess it depends on if you want to play your stereo in the park or just while driving. Also, I "think" I've seen some 100 amp alternators around somewhere.... either aftermarket or from newer Mopars (maybe late '70's Cordobas or something?)
Click to expand...
 
I wouldn't worry about it, just use good fused wires to your amp. The competition guys looking for max sound pressure with the extra batteries and capacitors are running over 4,000 watts.
 
Gentlemen,
Good old ohm's law should apply. P (expressed in watts) = voltage x amps. Or, P, in this example is 600 watts, so solve the equation for amps (assume the voltage remains resonable constant in this case is 14.4 the volts [engine running], so the formula is P/E = I or 600 watts /14.4 volts = 41.6 amps, but this is an instantaneous value. One should consider the RMS value (average), or approximately 1/2 of the peak value. Will the alternator be capable? Likely yes, but one should pay attention to the supply wire size, perhaps a size #10 AWG. Capacitors can supply the additional instantaneous current needed for peak demand, which will be fsirly large in terms of capacitance, ecpressed as MFD or microfarads or even farads...again connecting wiring must be sized for the anticipated load. Actual total loads must be factored in to the requirment.....vehicial lights, blower motor, wiper motor, ignition, etc. The actual alternator selection must be by the user....there are many different brands and capacities available. Any questions, please ask or PM me.
Regards,
RJ Renton
 
If you keep the ammeter in line, please feed everything from alt post, not the batt.
 
I bought one on Amazon (UNI-T) that will read up to 100Amps DC current. I've used it on stuff like my fans and fuel pump and it works. It was cheap, around $40. Of course it's Chinese and I don't expect it to last very long.
 
Shorthorse said:
I bought one on Amazon (UNI-T) that will read up to 100Amps DC current. I've used it on stuff like my fans and fuel pump and it works. It was cheap, around $40. Of course it's Chinese and I don't expect it to last very long.
Click to expand...

great deal! I'd keep a fire extinguisher handy when using meters from China. A friendly word of caution, cheap meters have been known to blow up in the users hands while testing higher voltages.
 
Glenwood said:
great deal! I'd keep a fire extinguisher handy when using meters from China. A friendly word of caution, cheap meters have been known to blow up in the users hands while testing higher voltages.
Click to expand...

Thanks Glenwood. Maybe I just found a reason to buy one of those selfie sticks.
 
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