Auto Alternators Rated and Constant Output

Alternators don't "just blow up". Short trips and city driving may not fully charge the battery, but it sounds like you've got other problems.

Maybe a smaller pulley on the alternator would help.

A typical alternator will put out between 13.5-14.5 volts.

Correct!!!

GA

I agree TCM.

Also, more voltage won't help. The range TCM stated is correct and adequate. Additional power requirements are usually rated by the alternator's current output rating, in my experience - ex: 65A alternator vs. 120A.

So... get a larger capacity aftermarket alternator. The only downsides will be how it effects the engine; less gass mileage, running less efficient, etc.
Those will be trivial compared to regularly replacing alternators.

...and can the existing wiring and protection arrangements cope without the vehicle catching fire?

Is the vehicle's insurance company up-to-speed with this modification?

As others have said, you have not given us enough information to diagnose, let alone solve, your problem.

"...does not put out enough power to handle the load I need to put on it..." why type of load did you put on it, a 2kW audio amp or ham linear?

"...I have to replace the thing every few months..." This is not a "common problem", most people realize after a few replacements that something else is causing the problem, kind of like replacing a fuse repeatedly without checking why it keeps blowing.

"...But I need more power..." How much more and why?

"...The Rating if it were 80 to 90% without damaging it and the diodes..." How do you know it's not outputting its rating and/or the diodes are failing? The electrical portion (stator and rotor) of most alternators is fairly basic, it's the voltage regulator that tells the alternator what to put out. Is the regulator and/or the diodes internal or external? Are they working properly?

You need to do a lot of checking instead of replacing the alternator. Any poor connection from the alternator to the battery to the sensing point for the regulator and/or a poor ground will cause exactly the same symptoms. A slipping fan belt will also result in the output falling off as the load increases since the belt doesn't slip until the load reaches a certain point.

If you don't want to do the hard stuff, then just install another battery and isolator in the trunk, and charge it every night.

are you running a 5000 W stereo? why such a huge draw???

When you say it burns up do you mean as in fire or in electrical "ka-put"?

To get a specific answer you should give a more specific answer. That would give you an answer more directed to you problem. GIGO = Garbage In, Garbage Out. Don't be personally offended by this, just a good rule of thumb to follow when posting a question. This is stated by some of the previous posters.

With fire engines and other heavy trucks that have heavy electrical loads it is common to determine what your heavy loads are and possibly repair the load item or tune it up. Check the wiring, is there any that needs to be larger? the usual next step is to replace the alternator with one having a larger output capacity, such as 300amps. There are numerous outlets that could probably have/get one with larger output for you model car.

Also have you considered using 2 alternators in parallel? If necessary here is a wiring diagram:

http://news.prestolite.com/drupaldocs/TSB-1035_Wiring_Diagram_4991-4992.pdf

These could be small enough to fit if you can make a modified bracket for them. Two standard 150amp alternators (a common size now) could provide 300amps this way. That should be enough to even power a 3,200 watt amp and have enough left over for some flashing LED's

Good Luck, Old Salt

It would be good to know the make, year and model of the vehicle, most manufacturers have optional high output alternators for unusual applications such as police, ambulance, options etc. My old Ford had a 125 amp. alternator where 85 was standard. Run it past us with more info..

If you look at the OP's previous thread on the same topic a few months ago, he stated that he drives a lot of stop & go in 90-100 degree temps with the AC going full-blast, plus has a refrigerator & 2 laptops running off the DC in his car. It's all that extra load that the alternator & battery were never designed to handle on a continual basis.

Car manufacturers design the electrical charging system to handle the typical max loads that might be put on the car, but not such extreme cases. If the OP wants to get that kind of service out of it, he needs to spring the big bucks for super heavy duty parts. Probably the best people to talk to are the ones who outfit cars with those gigantic stereo systems that ba-ba-boom down the road and vibrate your windows from a quarter mile away. They must deal with providing the additional power for the amps on a regular basis.

Oops didn't realize it was the same guy.

Well then the same advice holds true here as did in the other thread.

Talk to the high powered car audio guys. They make alternators that are 2 - 3 times the output capacity of his stock one that fit the same space.

Jimmyjoe, what are you running to draw that much power? I read one of these 'my alternator doesn't make enough power'. That person was running several desktop computers and a refrigerator. My suggestion was to replace desktops with laptops and replace the frig with an icebox or a propane powered frig. That is far cheaper than replacing your car with something that can deliver enough power. That guy needed to double his power and that is not a simple fix unless you just buy some kind of massive truck with a massive alternator.

I have the same issue with a 1998 Mustang Cobra.

The stock alternator is rated at 110 amps. On a hot day when the air conditioning is on with the fan on high, the voltage drops off considerably. The car has a serious power reduction at that time. Like there is not enough voltage to drive the injectors. I put on four rebuilt alternators from a auto parts store and the problem did not get any better. I purchased a new alternator from Ford and the situation improved, but it still exists somewhat. Could there be a grounding problem with it being a older car?

Is your car an older model, where as some of the connections through out the chassis may have a certain amount of resistance?

So, there is a serious power reduction when the engine is turning the air conditioner compressor, compared to when it is not turning the compressor...

Five different alternators did not improve this situation satisfactorily...

Yeah, I'll bet too much resistance in the chassis is to blame.

Would that be one from some years back when they rebodied Ford tempos with the 2.3L I4 pinto engines and called them mustangs?

If so you had at best 90 Hp to work with so yes I can see where running the AC would pull the engine down.

It would be the 4.6 V8 32 valve cobra engine. It came from the factory with 305 hp.

Noe that there is a blower on top of it, it's a little more.

Odd. my wifes 94 Mercury grand marquis has the same engine with less hp even and it has no trouble running the AC and its 100 amp alternator at max high settings.

Lower horsepower is the key. The Cobra has larger injectors and run a longer duty cycle, to deliver more fuel. The issue was not present when the car was new. The volt meter reads lower with every tax that is put on it. Much like my pay check. I have checked it with a V meter to confirm.

Just sying, because he may have some sort of undue load because of + going to - somewhere on the car.

Why is the type of vehicle a secret?

Go down to your local auto sound dealer with the car and ask them what alternators they use for their high wattage audio installations. They already know the answers.

If there is no room to install a bigger alternator, this is an obvious reason the small one overheats when stressed. The manufacturer will only solve issues of realistic worst case scenarios, e.g. recharging an almost empty battery at tropic climate, with all other installed electric loads on. (Actually this IS high stressing, especially if engine is at low rpm). But anything above that, is unrealistic use for a car alternator. Is there at least a possibility to improve flow and temp of the air it uses for cooling? Are there any modifications on car front? (ANY) S.M.

Here's a cheap fix. Add a second battery to the car. At night, hook your car up to an automatic charger to get the batteries fully charged for the next day.

Either this or do some major work fitting two alternators or some propane run equipment.

Good luck!

For 12V automobile alternators, the capacity output is primarily determined by the Stator (the stationary coil/windings within the case of the alternator).

Older vehicles commonly had outputs of around 55 - 60 Amps.

I was looking at this issue (albeit some years ago), & the auto-electrician advised that I could purchase a 100Amp stator to replace the original 55A one.

This involves removing the alteranator, dismantling it & reassembling it with the new higher capacity coil (stator) in place.

From memory this doesn't involve complicated tools, just basic home workshop eqpt & tools.

You can possibly get much higher than 100Amp stators. Check with your local auto-electrician.

They would obviously also be capable of fitting a larger coil to your alternator also.

Hope this helps.