Thread: Alternator Longevity

Originally Posted by Bugbyte

Depends on how many amps you are drawing. If you are drawing a significant amount of the capacity that the alternator is able to provide, yes, you could shorten it's life.

How many amps is your alternator? How many amps does your system(s) require?

The only option would be to get an aftermarket alternator that is bigger. Capacitors and bigger batteries don't solve this problem.

I'll second that statement. Capacitors will do nothing to help an electrically underpowered system. It was thought for many years that a cap would help to cushion heavy quick draws of amperage, but it has been proven that this statement is in fact false. Alma Gates removed all of the capacitors from her record holding SPL Bronco because she discovered that her SPL was actually higher without them in the system and that they were nothing more than another load on the system. The only benefit to a cap in a car audio system is that it helps to filter out some A/C ripple and in effect some noise, but in reality any cap more than 1 or 2 farad is completely pointless, except for maybe some show "bling".

^ isn't that possible through OBD2?

Stock alternators are not rated for continuous duty. In other words a stock type 140 amp alternator can only output full power for a short period of time. this is how they are designed and. that is a maximum rating at a certain rpm etc. If you are pulling a lot of power from the battery to the point where the alternator is having to work hard for long periods of time. then can overheat. they can also go into saturation where they simply go wide open and the voltage go up to 16volts. then they cook the battery and you start an endless cycle of replacing batteries and alternators. stock alternators just weren't designed with big big car stereo systems, where you have a large constant current draw, in mind. they were designed for the short large current draws like from a starter motor and a smaller constant current draw over time.

Heavy duty purpose built alternators are a different story. I have seen specialty alternators built for the car stereo market that will output full power all day, again as long as it is held at a certain RPM.

The Optima batteries while cool, and can be mounted in any position etc. have one major downfall not many people understand. They typically have a lower A/Hr rating per a given size then a conventional lead acid type battery. What this means is. that with a given fixed load, the optima battery will die faster. everyone talks about CCA, cold cranking amps, but that spec is meaningless when it comes to car stereo's. CCA is simply the measure by which how many amps maximum can be drawn from the battery for a very short period of time at 0 degrees. The A/hr rating which is often not published is the amount of current that can be drawn from the battery per hour for a given period of time.

there is just no substitute for size. Great big die hards have a very long A/hr rating. and in a car audio system will last much longer and your alternator will not have to work quite as hard. as the alternator can recharge the battery at a lower rate over a longer period of time. where as optima batteries of any color have a very short A/hr rating for the same group size. this means your alternator has to work harder to keep that battery charged! adding another optima would give you a longer A/hr rating and again your alternator would have an easier job.

as long as you dont run the batteries all the way down. IE less then 11 volts. in which case a proper wall type battery charger can bring the battery up to a level where the car's alternator can handle it without burning up.

Originally Posted by develguy

OK, so are you saying I'd be better off w/ a larger Die Hard than the Yellow Top if I'm using a stock alternator?

no, he is saying that for a large stereo, a large diehard sealed battery and a high output alternator would be best.