new alternator?

[Tmac]

Hello all, my current alternator is like 90 amps, I am running 2 1000 watt amps and a 300 watt amp for my mids, lights dim some but not alot. Should I upgrade or not? Also I bought a battery like 2 months ago and it already went dead, weird thing is I hardly drive the car alot, did it go dead from sitting or could it be something else? Thanks in advance.

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[johnecon2001 5,000+ posts]

Your battery.... hmmm. Dunno on that one, maybe it was just faulty.

As far as your "2 1000watt" amps go... are they really 1000 watts? Or are you looking at the peak ratings of them? Post the specs and model numbers.

You should try out the Big 3 before you go blowing your load early on a new alt.

 

[phyphoestilic 5,000+ posts]

If their rms ratings (about 2,300?) I would def. get a bigger alt, something 170+

 

[johnecon2001 5,000+ posts]

If their rms ratings (about 2,300?) I would def. get a bigger alt, something 170+

Quit passing out false info.

Based on some simple Jr. High math, you can easily figure out what he needs above his stock alt.

If his amps are putting out closer to say 300-350 a piece, and his speaker amp is maybe 200. You get 900 watts total. At 100% effeciency (which no amp has, its more like 40-70% or less) you need 65A to run the amps (900w / 13.8v = 65.21A).

But like I said, the efficiency level will be no where close to 100%. So you can take that 65A and cut it in half. That's on top of the stock alt, which probably has a little bit of leaway in it.

A 120A alternator would do fine for him... but he should still try the big 3 first.

 

[phyphoestilic 5,000+ posts]

Quit passing out false info.
Based on some simple Jr. High math, you can easily figure out what he needs above his stock alt.

If his amps are putting out closer to say 300-350 a piece, and his speaker amp is maybe 200. You get 900 watts total. At 100% effeciency (which no amp has, its more like 40-70% or less) you need 65A to run the amps (900w / 13.8v = 65.21A).

But like I said, the efficiency level will be no where close to 100%. So you can take that 65A and cut it in half. That's on top of the stock alt, which probably has a little bit of leaway in it.

A 120A alternator would do fine for him... but he should still try the big 3 first.

Where'd u get 300-350 a piece? he said 2 1,000 watt amps plus a additional 300 watt amp for his speakers. That's 2,900w if rms like I stated. (2,300w/13.8 = 166.67?) so.... WTF did u get ur stuff from? I understand he probably wont be running at full power all the time, so I said anything 170+ should be good because he needs power for other things in his car too.

The big 3 would help alot like u stated, but if the amps are drawing more power than his amp is recharging the battery with than eventually the bat will drain.

 

[Death By Bass 10+ year member]

Quit passing out false info.

ah, there was nothing wrong with that info...

he said, if it was RMS figures given, making it 2300watts rms total, to get atleast a 170amp alternator...

nothing wrong with that suggestion

 

[johnecon2001 5,000+ posts]

OP said he only gets light dimming with a 90A alternator. I've never seen a 90A alt that only got light dimming at a 2300w load.

Therefore, the assumption is made that he's going off of max power ratings.

 

[phyphoestilic 5,000+ posts]

OP said he only gets light dimming with a 90A alternator. I've never seen a 90A alt that only got light dimming at a 2300w load.
Therefore, the assumption is made that he's going off of max power ratings.

Well that's why I stated if he is meaning RMS ratings.....

 

[90accordman 5,000+ posts]

OP said he only gets light dimming with a 90A alternator. I've never seen a 90A alt that only got light dimming at a 2300w load.
Therefore, the assumption is made that he's going off of max power ratings.

I ran my Colossus off a stock alt in my mustang (85amp) and got light dimming when i cranked it

 

[regal8r 5,000+ posts]

your battery died bc of a little thing called parasitic current draw. even though the car is off and everything, there are somethings that still pull current from the battery i.e. radio presets/memory, PCM RAM, etc...

 

[thatkidbob 10+ year member]

^ maybe, but i doubt it... what most likely killed his battery (and what will kill his alt if those are RMS ratings) was the fact that the alternator wasn't putting out enough current to meet all of the electrical demands. Due to this, power is drawn from the battery and the alt never (or rarely) gets a chance to recharge the battery...

charge gets lower and lower, sulfates start to build up on the plates and... tadaa! dead battery.