TheSamba.com :: View topic - What High Powered Alternator to get? 75 / 90? What brand?

Mon Sep 19, 2016 11:23 am

Anyone know the amperage of a stock 74 super beetle Alternator?

For a long time I've wanted to replace my alternator with a higher power unit.

Never quite have enough juice for all my amplifiers + Lights
I want a simple swap, but I also want to get something that is reliable.
The only 90 amp unit I've found is on amazon made by "Eagle"??
The 75 amp unit is made by IAP

Any other known options?

I would much rather have the 90amp unit but if it is unknown reliability, I'm not sure.

Mon Sep 19, 2016 1:27 pm

Stock alternator was 50/55A.

Your other alternative is to have your alternator (or a Bosch or Motorola core) rebuilt by a reputable electrical shop. They would have to source the upgraded vr, but that should not be too hard. The rebuild should include replacing the bearings and polishing up the contact surfaces for the brushes.

By using a core instead of your own alternator you would minimize the downtime to just the R&R time for the alternator. If you use your own alternator you will need to send it off to be rebuilt and your wheels will be hung up until you can find the time to re-install it.

Mon Sep 19, 2016 2:17 pm

Reliability of aftermarket parts seems to be nonexistent sometimes. I can't say how reliable an aftermarket high-amp alternator would be.

I do seem to remember, though, that the Bus alternators put our more juice. But they were longer and therefore required different tins for the alternator itself. Or maybe that wad only with the generators. I'm not sure. But my first thought would be to see if you actually have an alternator and not a generator.

Mon Sep 19, 2016 5:19 pm

Get the Compufire Dual Cool 90 amp alternator. I have one in my 74 bug running 2 - 500 watt amps and it doesn't even flinch.

Tue Sep 20, 2016 6:35 am

As to reliability, That is the most frustrating part of old bug ownership. So much concentration on low cost out there, quality parts tend to be hard to find.

Nice amp setup... I'm running a RF Prime 1200.1 @ 1 ohm for the sub Turned out to be a good cheap amp. Replaced the inefficient Orion HCCA 2100 I had.

I used to run 3 batteries with the old 2100, but I've scaled it back a bit to just 1 Optima with the new class D amps. The Class Ds are so much more efficient than the old amps.

I'm also considering moving to LED lighting since that is when the trouble comes in. Can't run the radio and lights at the same time for very long!

Where do I find the Compu Fire Dual Cool 90 amp?

Tue Sep 20, 2016 7:10 am

I'm running led lights too, so I don't know what regular lights would do! ☺

I found a chrome Compufire from Moore Parts (I think). Just Googled it. But Amazon had some non-chrome last time I checked.

Tue Sep 20, 2016 10:10 am

The 74 beetle had a really good 50 Amp Motorola Alternator in it. It used an external voltage regulator. Jeeps used a similar Motorola alternator and their regulator will work with the Volkswagen Motorola Alternator. The current is limited in the voltage regulator though so even if you had the right voltage regulator the current may be some what less than 50 amps. I just use the VR-124 type with mine but I think they current limit to 12 amps or so. The Motorola Alternator can put out more current if you can find a regulator that will do it. Rock Auto.

Tue Sep 20, 2016 11:39 am

I'm always curious what you folks are running accessory-wise that require such massive outputs? apensity has some nice pics! What else do you folks run?

Robbie

Tue Sep 20, 2016 12:41 pm

My audio amplifiers can probably draw about 200A. So a much bigger demand than running the starter.
I've measured a hit at 250A for a short period on my old amp setup.
Lights + Fans (some for the A/C)+ Fuel pumps draw a little more current.
Throw in a rainy day (wipers + lights + A/C + fuel pump+ Radio) idle in traffic and you sit pretty negative.

A 50A alternator may not put out that much at idle. Maybe 20A if you are lucky.

Tue Sep 20, 2016 12:50 pm

http://www.jaredmonaco.com/bugs/bug_box.jpg

+

http://mlb-d2-p.mlstatic.com/amplificador-orion-21...uare=false

Tue Sep 20, 2016 1:46 pm

I use the same alternator as apensity, it works fine and I'm pleased with it.
New wiring, LED/COBB/SMD lighting and a moderate sub/amp stereo system, no issues and I know that I will never really tax the output.
Whether or not the rated output is needed, probably not, but in all cases I strongly urge the incorporation of a circuit breaker in the system to ensure some protection.

Wed Sep 21, 2016 5:37 am

Did you get the polished one or Raw? My current alternator is actually painted and looks really good like that. Also I have the serpentine belt kit.

My question about the polished one, have you hand any tarnishing issues?

Wed Sep 21, 2016 8:05 am

I have the chrome one, no tarnishing or any cosmetic issues at all.

Wed Sep 21, 2016 7:31 pm

JMon wrote: My audio amplifiers can probably draw about 200A. So a much bigger demand than running the starter.
I've measured a hit at 250A for a short period on my old amp setup.
Lights + Fans (some for the A/C)+ Fuel pumps draw a little more current.
Throw in a rainy day (wipers + lights + A/C + fuel pump+ Radio) idle in traffic and you sit pretty negative.

A 50A alternator may not put out that much at idle. Maybe 20A if you are lucky.

The nice thing is that a lead acid battery can happily handle 200 amp's when the base calls for it even with high base music the demand is less than 40% giving the battery time to recharge at 10 or 20 amps if it starts to get low. That being said the more solid a power supply for a low output impedance Amp the better. If I were doing this I would want a -12 volt supply in addition. Perhaps modify the Delta Wound Alternator by patching it's Internal 3 phase AC directly into an External Schottky diode bridge to provide the -12 volt and +12 volt rails for a balanced amp.

Thu Sep 22, 2016 8:22 am

At one point I almost put a 2nd alternator in the car.
The "Big Boys" have many...

http://s116.photobucket.com/user/alpinemayn/media/2010%20Electrical/Tahoe_Quad_11.jpg.html

Also, most high powered amps don't run -12 to +12 rail voltage. Generally much higher than that. Thus the need for the internal DC-DC converter section of the amp. The last one I actually measured was somewhere over +-40v

That is the nice thing about the batteries, is they can generally take the intermittent hit and allow charging outside the peaks.

Thu Sep 22, 2016 9:56 am

Here is my list of part numbers and prices I've found:

----------
Compu-Fire 90A
Dual Cool
58620
Same as EMPI 9460-7 $275
---------
Compu-Fire 90A
Dual Cool
58630 Polished
Same as EMPI 9462-7 $295
---------
EMPi 90A
9458-7
AL82
?? fans??
Made in USA $239
---------
EMPI 90A Single Fan
9458-7
USA $210
---------
EMPI 90 Single Fan
Polished
9459-7
USA $290
---------
EMPi 90A China
Chrome
9463-7 $219

Thu Sep 22, 2016 10:51 am

It's an interesting idea. Running two alternators. Running one even split to produce a -12volt supply is not going to deliver more power than it would wired right. But with two alternators you would truly double the power. I guess most of the off the shelf Amps for Autos are designed to work with some kind of inverter because to get say 500 watts of peak power audio into a 8 ohm speaker the math demands it. I=E^2/R or 500=4000/8 and the Square Root of 4000 is the voltage needed. My calculator says it is 63.25 volts. Yeah -40, +40 volt rails would do it.

That would only require about 8 amps out of the inverter because P=I^2*R or 512=64*8 So the question becomes how much current does the inverter draw on the 12 volt system to make 8 amps?

It's going to be close to 42 amps and that is not calculating the power factors.

Fri Sep 23, 2016 5:49 am

Landed up ordering the Compu-Fire 90A Dual Cool 58630 Polished...

Still not sure about the polished part. Choose polished because I won't have to paint.
My current alternator is painted the color of the car & dog house. Looks nice. Not many people do that so it is different. If the polished doesn't look nice, I'll just have to do a bunch of sanding and repainting.

Additionally, I'm going to run a new ground directly from the alternator to the frame of the car. That way grounding doesn't have to traverse the alternator stand-> transmission ground strap. Alternator stand->Alternator link is what I'm most concerned with.

Sun Dec 22, 2019 9:04 pm

apensity wrote: I'm running led lights too, so I don't know what regular lights would do! ☺

I found a chrome Compufire from Moore Parts (I think). Just Googled it. But Amazon had some non-chrome last time I checked.

Any update on this. Is the alternator still holding up?

Any problems arise?

Wed Jan 08, 2020 7:53 am

Check out this thread of the detailed issues I had:
https://www.thesamba.com/vw/forum/viewtopic.php?t=665414

Short of it is, The compufire went back the Empi went it.
9463-7: alternator bug 90 amp CHROME China Empi

The Empi is still working strong with no issues. That being said, I don't think I have driven over 500 miles in the past year.
It supports the lighting and Car Audio Amps really well....