Alternator Upgrade vs Stock questions.

[ThxOne Premium Member]

My car has a stock 90a alternator and I know that the manufacturer determined this to be adequate for this cars needs with ALL electrical loads being used i.e. A/C, Lights etc. I have added the load of the aftermarket car stereo into this mix. I can listen to my radio without any real issues but I know I am leaving some amplifier power on the table. I say this because the same subwoofer amp and subs I am using now which are in a trunk of similar size and using the same enclosure do not hit as hard or loud as they did in my G6's which had all the same electrical upgrades (Big 3/4 extra ground) all same size cables as well. The differences are the G6's had normal lead acid batteries but had a 125a stock alternator. This car is 90a and I upgraded to an AGM.

So I guess what I am getting at is how down on power are my amplifiers? All RF Punch with the sub amp being the Prime. 400x4 - 500x2 - 1200x1. These are the amps. I will be swapping out the sub amp for my Smart3. I know the rule, it takes power to make power and I don't even want to attempt the smart3 yet until I get the new alternator. This brings me to another question. With the new alternator will it be enough to allow the amps to make full RMS power? Will it be safe to substitute the Smart3? The new alternator will be 200a @ 1200rpm and 100a @ idle. I am not above adding a second identical AGM in the trunk. Will an additional 110a do the job?

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[metalheadjoe 10+ year member]

Your questions are valid but there is no definitive answer because there are too many variables; anyone who pretends to know is speculating.

As much as I hate generic answers, the generic answer is correct in your case: measure voltage at your amp and decide when you need more power.

If stereo is more important to you than gas mileage, you should find tuning info to adjust idle speed.

 

[spokey9]

I ran my smart 3 off one battery with ho alternator for a bit but I had the subs wired go 4ohms without losing voltage...I'd say run it and see what you're getting at the amps...you can always add the 2nd battery if needed

 

[mat3833 10+ year member]

Rough numbers here, but the math is simple.

Double the power is a 3db increase.

So with 12v instead of 14.4 you are probably leaving between 10 and 30 percent power on the table. If you are expecting 1000w you may only be getting 700-900w. That's really not a huge difference when you consider music is dynamic not sine wave.

Matt

Edit, your amps may have birth sheets that would telk you power output at 12 and 14v.

 

[HardofWhoring]

Your alternator is not effecting that in any way. All your alternator does is recharge your battery. If your stereo draws more than your alternator can recharge, it will only draw from the battery (the storage bank). Your alternator will just recharge it as best it's capable of. If you added an AGM battery in the new setup vehicle, then that battery is capable of everything you need. Your problem is not in the alternator or battery.


You could use a larger alt, but that's not what is restricting your setup. not sure if that's 400 +500+1200 = 2100 / 14.4v = 145.83 amps /.85 amp efficiency = 171 amp draw for those 3. You should be good with a 200 amp alt. If you have your head lights, AC, engine running, brake lights, something charging off the cig lighters, and you have a heavy bass track, while below 1200 such as sitting in traffic for a half hour or more without picking it up, you would probably need to turn it down to let your alt catch you back up. Anything other than that highly compromised situation, and you are probably good.


What is different about the new setup? Unless you used the same head unit, did you reset your gains?

 

[ThxOne Premium Member]

Your alternator is not effecting that in any way. All your alternator does is recharge your battery. If your stereo draws more than your alternator can recharge, it will only draw from the battery (the storage bank). Your alternator will just recharge it as best it's capable of. If you added an AGM battery in the new setup vehicle, then that battery is capable of everything you need. Your problem is not in the alternator or battery.


You could use a larger alt, but that's not what is restricting your setup. not sure if that's 400 +500+1200 = 2100 / 14.4v = 145.83 amps /.85 amp efficiency = 171 amp draw for those 3. You should be good with a 200 amp alt. If you have your head lights, AC, engine running, brake lights, something charging off the cig lighters, and you have a heavy bass track, while below 1200 such as sitting in traffic for a half hour or more without picking it up, you would probably need to turn it down to let your alt catch you back up. Anything other than that highly compromised situation, and you are probably good.


What is different about the new setup? Unless you used the same head unit, did you reset your gains?

The two mids and highs amp and the smaller alternator are different. I ran my Soundstream 4 channel and this sub amp in the G6's. Still 3-way up front, two subs in the back. Same head unit. Gains all set/reset. I also ran a RF 3Sixty.3 DSP. I am not now.

 

[Grimmjoww]

Really solid answers already. Only way to know is to measure voltage usage with your system at full tilt while car is at idle. And that can change based on idle speed vs 1500rpm and up on the engine. To be safe I would run a decent 180+ alternator and a agm battery in the back.

 

[hispls 5,000+ posts]

the generic answer is correct in your case: measure voltage at your amp and decide when you need more power.

This is really the only correct answer since we have no way to account for the other variables.

the same subwoofer amp and subs I am using now which are in a trunk of similar size and using the same enclosure

If you're not talking about the same exact year/make/model vehicle with the exact same amp/sub(s)/box I wouldn't even consider that as evidence of anything.