Battery/alternator life expectancy with new setup.

[RSDXzec 10+ year member]

Today I'm getting my alternator rebuilt so I'm going from 50Amps to 85Amps. My plan is to run 1000wrms at 1.34ohms so with 80%amp efficiency I should drain at most (on 50hz -0db bass hits) about 34Amps. My battery is rated at 325CCA and 45RA and was bought last year.

I'm also going to be upgrading to 4ga wire to the amp and I have 2/3 of the big 3 wires upgraded to 2ga, the only one missing is the +ve batt to alt which I believe is around 6ga. Haven't done it yet because I'm not sure how to go about it, because the +ve batt is actually connected to the starter motor.

I just wanted to know if I could go another 2-3 years without needing to replace the batt/alt on this setup. As far as I know 1000wrms is alright on stock electrical systems but I figured stating my specs here I can get a bit more feedback on it. I can turn down the power draw if I need to.

I'm also concerned on how battery life is affected by being drained, in almost a year of use this battery has seen it's been drained 2 times. As far as I know they have a life expectancy of around 5 years. The brand is "Century". Though with the better alt I'm betting it'll get charged up nicely and it won't be much of an issue anymore.

Cheers.

Click to read more...

 

[THATpurpleKUSH 5,000+ posts]

you will def need to upgrade the batt with that small of an alt.

 

[RSDXzec 10+ year member]

you will def need to upgrade the batt with that small of an alt.

with the 50Amp or 85Amps?

and how many RA would you recommend?

Cheers.

 

[RangerDangerV2 5,000+ posts]

alt is tiny.... get a 300 amp and call it a day.

 

[RSDXzec 10+ year member]

alt is tiny.... get a 300 amp and call it a day.

that's as big as it gets for my car, tried to get them to make it 120Amps but it would've been too complicated/too many modifications etc. Also don't have much room to work with on an 84 Astra so any better than 85 Amps is out of the picture. So now I'm looking at batteries, my current one being 45 Reserve Amps I'd like to know how it would hold up.

Staying with this setup for 2-3 more years once I get a good car then I can put in a ho alt.

 

[Drummer65 10+ year member]

Today I'm getting my alternator rebuilt so I'm going from 50Amps to 85Amps. My plan is to run 1000wrms at 1.34ohms so with 80%amp efficiency I should drain at most (on 50hz -0db bass hits) about 34Amps. My battery is rated at 325CCA and 45RA and was bought last year.I'm also going to be upgrading to 4ga wire to the amp and I have 2/3 of the big 3 wires upgraded to 2ga, the only one missing is the +ve batt to alt which I believe is around 6ga. Haven't done it yet because I'm not sure how to go about it, because the +ve batt is actually connected to the starter motor.

I just wanted to know if I could go another 2-3 years without needing to replace the batt/alt on this setup. As far as I know 1000wrms is alright on stock electrical systems but I figured stating my specs here I can get a bit more feedback on it. I can turn down the power draw if I need to.

I'm also concerned on how battery life is affected by being drained, in almost a year of use this battery has seen it's been drained 2 times. As far as I know they have a life expectancy of around 5 years. The brand is "Century". Though with the better alt I'm betting it'll get charged up nicely and it won't be much of an issue anymore.

Cheers.

How did you figure only a 34 amp draw? Its closer to 80-90 amps

And how are they rebuilding your alternator to 85 amps? Are they just rewinding the stator or changing out rectifiers as well?

 

[RSDXzec 10+ year member]

How did you figure only a 34 amp draw? Its closer to 80-90 amps
And how are they rebuilding your alternator to 85 amps? Are they just rewinding the stator or changing out rectifiers as well?

I used I=sqrt(P/R) so I=sqrt(1000/1.34)

derived from P=IV and V=IR

so P=I^2R rearranged to the eqn above.

once I find I, the value is divided by 0.8 to account for the 80% efficiency, my amp is rated at 85%.

And they're replacing the rotor and stator as far as I know. I'm not too sure on the details.

 

[Drummer65 10+ year member]

I used I=sqrt(P/R) so I=sqrt(1000/1.34)
derived from P=IV and V=IR

so P=I^2R rearranged to the eqn above.

once I find I, the value is divided by 0.8 to account for the 80% efficiency, my amp is rated at 85%.

And they're replacing the rotor and stator as far as I know. I'm not too sure on the details.

I see what you mean but your getting confused

You use your equation to figure out the amp draw from the outputs of your amplifier, NOT the amp draw from your battery to the amplifier. So at 1000 watts at 1.34 ohms you get about 27 amps. That is around the amps you will see from the outputs of your amp to the sub with about 36v. That is without box rise tone and all that ****.

If your drawing 1000 watts from your amp your drawing 1000 watts, doesn't matter if its at 4 ohms or 1 ohm. So to make 1000 watts at 12v you need 83 amps.

What amp are you using? I'm guessing your amp is 85% at 4 ohms not at 1 ohm. What you need to do is find the power efficiency at your ohm load. If it is 85% then you will be drawing roughly 95 amps. Of course your voltage is changing so these numbers are all hypothetical.

What car do you have? Generally shops just rewind the stator without changing the rectifiers or voltage regulator which will significantly lower the life of your alternator. You will probably see less amps at idle as well. I would bring an ammeter with you just to make sure its putting out what they say it will.

 

[RSDXzec 10+ year member]

I see what you mean but your getting confused
You use your equation to figure out the amp draw from the outputs of your amplifier, NOT the amp draw from your battery to the amplifier. So at 1000 watts at 1.34 ohms you get about 27 amps. That is around the amps you will see from the outputs of your amp to the sub with about 36v. That is without box rise tone and all that ****.

If your drawing 1000 watts from your amp your drawing 1000 watts, doesn't matter if its at 4 ohms or 1 ohm. So to make 1000 watts at 12v you need 83 amps.

What amp are you using? I'm guessing your amp is 85% at 4 ohms not at 1 ohm. What you need to do is find the power efficiency at your ohm load. If it is 85% then you will be drawing roughly 95 amps. Of course your voltage is changing so these numbers are all hypothetical.

What car do you have? Generally shops just rewind the stator without changing the rectifiers or voltage regulator which will significantly lower the life of your alternator. You will probably see less amps at idle as well. I would bring an ammeter with you just to make sure its putting out what they say it will.

Ah yep I see what you're saying

I'm using an Audiopipe APSM-1500, and my car is a 1984 holden astra. I was told the alternator would have the rotor and stator replaced and the voltage regulator if it needed to. I think he also replaced a few connectors that were faulty.

The mechanic has tested it and said it's outputting pretty good even at lower RPM, I'm going to try and get some numbers tomorrow when I go to pick it up.

Any chance you could recommend the Reserve Amps necessary on a battery to keep this running fine?

 

[Drummer65 10+ year member]

Ah yep I see what you're saying
I'm using an Audiopipe APSM-1500, and my car is a 1984 holden astra. I was told the alternator would have the rotor and stator replaced and the voltage regulator if it needed to. I think he also replaced a few connectors that were faulty.

The mechanic has tested it and said it's outputting pretty good even at lower RPM, I'm going to try and get some numbers tomorrow when I go to pick it up.

Any chance you could recommend the Reserve Amps necessary on a battery to keep this running fine?

A battery with over 100 Ah will work fine, reserve amps are different then Ah take note of that. Your more concerned about the discharge rate of the battery, you want a battery that can discharge fast because you will be pulling more amps then what your alternator can produce. Although pricey, look into XS power and try to get one battery for the trunk. A Deka or C&D would work as well but you will see more of a voltage drop as they can't discharge as fast as the XS power

 

[RSDXzec 10+ year member]

A battery with over 100 Ah will work fine, reserve amps are different then Ah take note of that. Your more concerned about the discharge rate of the battery, you want a battery that can discharge fast because you will be pulling more amps then what your alternator can produce. Although pricey, look into XS power and try to get one battery for the trunk. A Deka or C&D would work as well but you will see more of a voltage drop as they can't discharge as fast as the XS power

Thanks for the heads up.

Been looking online and RA/RC is a little less than double the Ah so I'd say with 45RC my batt should have close to 25Ah. I can't find the rating on it.

Do I really need 100Ah for 1000wrms?

I found this "To achieve 1000 watts RMS you will need a battery with about 50AH rating." here Car Audio Capacitors vs. Power Cells - Knowledge Base

So basically with a second battery of the one i have now should that hold up?

I've looked into Deep Cycle batteries and a 100Ah Century Deep Cycle Batt is about double the price of my current Batt.

The other option I've considered is to run it at half power for daily then push it to max for demos.