Bigger alternator

[sbkvp]

After some advice here. I'm pretty sure I'm going to need a new alternator for my new audio setup. I'm going to be using an Earthquake PH-D3 (3000WRMS) and an Alpine MRV-1507. The MRV-1507 draws for a memory up to 80A and the PHD3 about 250A (if I remember correctly).

The VP bosch alternator is (again, memory here) about 85A. Clearly for my engine not to keel over and die, I'm going to need a bigger alternator. Will have 1-2 deep cycle batteries on isolation too.

But my question - what should I do for an alternator? I think I read somewhere that Bosch make an alternator that puts out up to 250A at 2500rpm. I think I also read that you can get two 120A alternators piggybacked that will fit into the standard engine mount. Can anyone help me out with this?

I'm *hoping* I've got this Q in the right forum - if not - sorry!

Thanks in advance,
Sam

[semi]

3000/12=250. (P/V=I) so 250 if your amp is 100% efficient. which its not. Id say maybe 75% efficient? at a guess. so 250/0.75= 333A.

BUT. I doubt you would be running at this level for extended periods of time. 250A total seems pretty decent. halfway seems the most you would run your subs with normal use.
So you would probably be looking at 100-150A current draw. Id say that the one 250A alternator would be fine, and would be less hassle than trying to run 2x120A

[garfa]

ok probably get a clamp to measure the normal current when you have the music at its normal volume. then decide if you need a bigger output alt and how big you really need.

[dephilile]

I think D class amps are about 80% efficient because of the way the transistors switch hard on or hard off. Other classes range from 40 to 60% depending on the design.

[sbkvp]

Yeh the PHD3 is 85% efficient. Not sure on the efficiency of the MRV1507.

Thanks for your help guys.

Question: Which alternator to use, roughly how much is it, and where can i get it from?

Thanks

[StoneX]

Don't even bother looking until you've installed the stereo... There are so many people running massive amounts of power from amps and don't have an upgraded alternator. Just see if you have any problems before worrying about it.

I've got 2400Wrms and 400Wrms in my VT and have had no problems over the 2 years it's been installed. You wil have a bit more power, but not enough to require an upgrade, in my opinion. You'll never be drawing anywhere near maximum current unless playing test tones and then your car should be off anyway so no alternator running.

[grafxworld]

If your running that much current thru a stock alternator it will fry the regulator and windings and remember a battery is a storage device, the recharging is the alternator
and if it's trying to recharge a few deep cycle batteries on top of the stock one you will have problems with dead batteries and or shorted cells isolated or not. you need to run the engine a for a long time to charge deep cycles

make sure you have a big ground wire running from alt. bracket to battery ground and the current wires match that one. and you better run a huge cable to amps or boot mounted batteries O gauge or bigger or the wiring becomes the fuse

the weakest link in the chain will fail , you want to fuse the front with curcuit break close to battery if thats you main power source.to protect the car not the amps
0 gauge wiring with a short and lots of amperage coming from the batteries will do some REAL welding and fires

a 250 amp alt. will cost a large amount of cash, get it if your serious about building a huge system (sound off - show cars etc.)

your alpine amps aren't current limited , they make more power at higher voltages,
not positive about earthquake and the new power supplies on those, but you should be safe expecting a average current draw at a mid volume to be 100-150 amps

what OHM load are you running your amps at ? the amps will draw a lot more average current at lower OHM loads ? the power fuses in amps are a a max rating when you have a short or low OHM load which causes a current draw to sky rocket and protect the transitors from damage, dont base you fuses on those , use a lower amp fuse to protect your car

you also need at around 3-5 farad total capacitance to buffer the current draw during bass hits or your bass will sound muddy and the cars computer,lights etc will suffer.
(I've got 3k watts running off my VT upgraded alt. and the computer starts to malfunction at the stop light at idle with the volume cracked up to nuke the car beside me, causes it to surge during bass hits, system not fiished up yet needs a capacitor bad and real battery( Gates or power cell gel cell)

I'm a master certified installer from america who used to own a car audio shop for 10 years if you want heaps of suggestions, we used to build show cars for sony,rockford,orion,PPI)

[StoneX]

Why hasn't my reg or windings fried yet then?

2800Wrms (2400 x 1 @ 1 ohm and 200 x 2 @ 4 ohm) + stock alt + deep cycle battery + 2yrs = no probs.

[grafxworld]

Deep cycle battery is a huge buffer for the alternator, a stock battery and stock alternator will fry , not right away but over time and if you pound alot at night with ac and lights etc on, the voltage regulator ends up packing it in.
sometimes sticks wide open 16volts or more and sometimes it just blows and the voltage output = 0

I would really like to see your cars lights at night while pounding, bet they flicker a bit on bass notes if you have a amp driving your subby with that kind of "TRUE "power. without getting into electical theory which would go way over the head of most people here , if you like I will show you in Ohms law
in which case your amps at RMS power should draw 233.33 amps at 12v and 1 OHM with 2800 watts RMS power?
http://www.the12volt.com/ohm/page2.asp
which puts your alternator in the negative current already, not including lights engine,etc.

what brand of amps are they ? some amps say 10,000 watts but only for a millisecond not RMS (watts at average volume level ) just checking not putting you down.

I think the point is lost , 250 amp alternators aren't cheap and can be over kill for all but the biggest systems,unless you sit pounding with the engine off for a while, and drive short distances (makes it tough to charge up batteries on short trips)


my many years of installing stereo's being a master cert.installer has taught me a lot , but a BA in advanced electronics helps too.

[grafxworld]

http://www.zena.net/htdocs/alternato...inf2.shtml#Top
good site for more info on big alterantors


Car stereo review explaining everything about your topic
http://www.termpro.com/articles/electsys.html

[StoneX]

Directed 2400Wrms mono amp, but they've been measured putting out up to 2600Wrms and an Audison LRx2.500 which are known to make their rated power aswell.

You would know that amps very rarely draw their maximum current. I'm sure my amp has probably never made 2400Wrms and if it has it would be for milliseconds as music is so dynamic. But yeah, my headlights dimmed like mad when running a 40Hz tone through my old SPL sub

No need to give me links, I know ohms law being an elec technician myself.

[grafxworld]

Oh looked it up your amp puts out 1200 watts at 1 ohm rms

looks pretty nice specs and looks, price is really good too.
they make all the equipment now for Orion,PPI, ETC.

[StoneX]

Don't try to tell me how much power my amps make, I don't have a current model

The rest of the specs are pretty average though

[Tasmaniak]

master certified installer? In Australia? Huh? What qualification is that?

[grafxworld]

Master certified in America not OZ!!
http://www.mecp.com/home.asp
12 volt king , looks like your in USA
Have you ever heard of Excaliber sound in Denver (We used to put ultra high end equipment in Ferrari's,Lambos.. etc. build show cars for sound offs, build manuf.show cars in the 90's, or the Car Stereo Center in Billings,MT ? these are a few of my earlier jobs before opening a private shop for car audio and home theatre in Denver, and yes I do live in OZ now but car audio at this point is a passion not profession anymore

[grafxworld]

calm down Stone X
noy trying ot put you down

[Tasmaniak]

grafxworld, no, I havne't heard of them, I'm relatively new to the US myself. I've been moving back and fortht between the two countries for a couple of years now. I'm higghly surprised....actually I fell of my chair almost.

I too am Master Class certified via the MECP. But to be honest. I don't think much of the certification program.

[grafxworld]

I agree , when I did it back in 90's it was the thing to do , only a few existed and it was a huge honor to be one, pay was much better, close 100k a year on a good year,I was considering opening a car audio customization shop in Adelaide , one to rival an american shop. they could use one here , the money is being spent on equipment thru 10 different shops.
need a one stop shop to customization , any thoughts on that ?

[Tasmaniak]

What has always amazed me with the various countries that I have worked in is the god like status an installer can acheive by proving their worth.