Efficiency question

[brokeitagain 10+ year member]

ok now a question of efficiency

i have purchased a memphis prd 1.1000 07 model

according to the math at 13.8 volts it draws a theroetical 72 amps. now if it is only ~70% efficient the current draw will be 30% higher correct?

I havent figured the amperage draw at lower voltages because i am simply trying to understand this better. i am trying to figure out how many amperes my alternator needs to be able to produce. The shop that is building alternator says not to go too high due to low rpm charging issues i have with the ho alt i have.

I thought i knew alot about audio stuff until i got into better equipment

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[dipitydoo 10+ year member]

Just over 100amps at 70% efficiency at 1000w. Unless you are building a competition system, the stock alternator should be fine...

 

[brokeitagain 10+ year member]

my stock alt is 100 amps, i have a/c, headlights, fuel pump, computer,and every thing else electrical that draws current, thats 70 amps alone, so im guessin 200 amps is gonna do it

 

[thch 10+ year member]

It will scale with the inverse, eg:

50% efficiency means:

current/0.5 = actual

70% efficiency means

current/0.7 = actual.

or

72/0.7 = 103A

 

[dipitydoo 10+ year member]

my stock alt is 100 amps, i have a/c, headlights, fuel pump, computer,and every thing else electrical that draws current, thats 70 amps alone, so im guessin 200 amps is gonna do it

You don't need to match up alternator output with current draw of the amp. The battery will buffer the current demand once the alternator's output is exceeded. Again, unless you are in spl competitions, your stock alternator should be fine.

 

[brokeitagain 10+ year member]

i think not as i am seeing less than 10 volts at night with air, stereo, headlights on under driving conditions .My ho alt was 300 amps at 2000 rpm

and only about 50-60 up too 1200 rpm.

if u were driving this you would agree that the stock alt. is not sufficient for anything but a stock system.

 

[Sunfire01 10+ year member]

less than 10? I'd check that with a multimeter in your driveway with all acc. on. I doubt that is right, or your car would be shutting off.

 

[dipitydoo 10+ year member]

I would check to make sure your electrical system is functioning properly, like your battery and alternator. You might also be getting instantaneous dips in voltage drop, which may or may not be normal.

 

[KickerSoItBump 10+ year member]

One thing I never did while bumping my subs really hard is turn on the air... thats major draw.

Do you seriously run that many electronics in your car (that are necessary) to necessitate a HO alt, with a 1000w amp?

I was running 1200w fine on my stock 130A.

Stop multi-gang-banging your alternator and you'll b perfectly fine.

 

[brokeitagain 10+ year member]

ok whatever theres always a group of smartasses here when someone asks a question. i have checked with a multimeter (Snap-On Vantage as a matter of fact)so i know what i am getting

thank to the ones that have answered my questions without telling me im stupid. assholes

 

[brokeitagain 10+ year member]

btw brand new yellow top, and a remanufactured ac delco alt

 

[mlstrass 5,000+ posts]

Have you done the BIG3??? Good batt/alt won't help much if the stock wiring is too small or corroded...

 

[12VoltInstaller 10+ year member]

It will scale with the inverse, eg:50% efficiency means:

current/0.5 = actual

70% efficiency means

current/0.7 = actual.

or

72/0.7 = 103A

This guy is on the money.

If your running into the low voltage low amperage situation at low rpm, find an alternator pulley that is a fraction smaller. I do not know the equation for this ratio, but I am under the impression that this will only affect you adversely if you have a high revving engine that will spin the alternator past its efficient working rpm at extended periods of time (long highway trips) = thermal failure.

It would either be that or turn up your slow idle on the vehicle ever so slightly. (Not my recommendation)

Why would someone suggest wire if you are now to the point of asking the questions regarding efficiency and duty cycle of your alternator? He's been down that road man....hes got the hose...he wants a bigger hydrant!

Have you used your meter to inspect your voltage levels with these accessories running while you increase rpm? It might not just be a revs per minute in relationship to the alternator...it could be something else..... try the meter first...then on to the next.

If you want to run all those ACC. go right ahead...who says you can't...if you got it...flaunt it.... you wouldn't run all that during an SPL comp anyway.

Its all about bumping your Cake and having A/C too!

//content.invisioncic.com/y282845/emoticons/peace.gif.2db28b618ed8d1964ebbe2f5021d2c39.gif

Holla back.....

 

[///M5 10+ year member]

Have you done the BIG3??? Good batt/alt won't help much if the stock wiring is too small or corroded...

Yes indeed. What you have for an amp should easily be supported by a stock alt if the wiring is up to par.