Can an Optima Red Top (or AGM Equivallent) kill an alternator?

[ChiGGz]

I've done some reading and apparently AGM batteries can outdraw an alternator for extended periods of time, thus killing it.

What sort of situation will this or could this happen in?

Any cons of using AGMs?

 

[zilo900]

Ive never heard of this before...
It also doesn't make sense, how would a battery-which is recharged by the alternator- can do any damage to the alternator..

The alternator runs off the engine rotating, and generates power for the iginition, and the cars electric systems, while sending power back to the battery. I just dont see a reason how an alternator can make a battery go bad or shorten its life

There are many factors as to why a battery can prematurely fail though, mostly all of them human error related. (i.e. letting the battery completely drain several times; the alternator belt not being tight enough to recharge the battery; the alternator not functioning properly enough to even recharge the battery)


On a side note I've had an Optima yellow top for 3 years and it has even sat for 3 month, and 5 month periods and still cranked the car with no hesistation

 

[boosted92laser]

A battery can kill an alternator. If the battery has a short in it, the voltage has nowhere to go and it can shoot right back to the alternator and fry it and possibly the computer. Thus the reason why you don't unhook the battery with the car running. A bad alternator can also kill the battery. If the diodes go out in an alternator, it will try to charge as AC instead of DC.
I have never heard of an Optima battery killing an alternator though, and I've been working in automotive retail for 8 years.

 

[ChiGGz]

Thus the reason why you don't unhook the battery with the car running. A bad alternator can also kill the battery. If the diodes go out in an alternator, it will try to charge as AC instead of DC.

I think you're incorrect on that one. An unhooked battery can cause an alternator to die due to current spikes produced by the alternator. The battery acts as a filter to safegaurd the alternator from this.

I do think my diodes are gone though, cause my alternator produces 14 v (or w/e the correct value was) but when I turn my accessories on, the voltage drops and the alternator doesn't make an attempt to bring the voltage back up. Can someone verify that theory?

 

[DGajre777]

I do think my diodes are gone though, cause my alternator produces 14 v (or w/e the correct value was) but when I turn my accessories on, the voltage drops and the alternator doesn't make an attempt to bring the voltage back up. Can someone verify that theory?

If the voltage drops and the alternator doesn't make an attempt to bring the voltage back up that means that your voltage regulator inside your alternator is dead. My alternator did the same thing, and after I replaced it with a rebuilt Mitsubishi alternator everything is fine. The volts on your car should be between 13.6-14.2 with the car on, and 11-8-12.2v with the car off.

I do not suggest that anyone disconnect the battery while the car is running. This can make the alternator blow up and also kill the ECU. If you want to test that you alternator is working get a voltmeter or connect a digital volt gauge.

Back to the original post, I don't see how a dry cell battery can kill an alternator. Some reading material...

Part 2: The Alternator

As we have discussed before, the battery is the heart of your electrical system. But you need something to keep the battery charged or it will lose its charge and die. This is the job of the alternator. The alternator produces electricity and delivers this electricity to the battery and maintains a full charge at all times. If the voltage produced by the alternator goes above 13.5 - 14.5 volts, the battery will be ruined very quickly. It's the job of the voltage regulator to keep the output voltage between the 13.5 - 14.5 volt range.

An alternator is the device used to produce the electricity the car needs to run and to keep the battery charged. The alternator uses the principle of electromagnetic induction to produce voltage and current. The four main parts of the alternator are the Rotor, Stator, Diode Pack, Voltage Regulator and an Ammeter or Indicator Light to inform the driver of any problems. All of these parts must be in good working order for the alternator to do its job. Let's take a look at each of these parts and what they do.

The rotor is basically a magnet that rotates inside thousands of loops of copper wire wound around a core of iron. This wire wrapped iron core is the stator. As the rotor spins inside the stator the magnetic lines of force cut through the copper wire inducing a voltage. This is the voltage that will go to the battery.

The only problem is this produces AC current and your car runs on DC current. So we need something that will convert the AC current to DC current. This is the job of the diode pack. A diode is an electrical one-way check valve that will let current flow in only one direction. The typical diode pack uses four diodes to accomplish this. AC current is feed in on one side of the diode pack and DC current comes out the other side. The diode pack also works the dash ammeter or indicator light.

Okay, now that we have a DC current that the car can use, we need a way to control that current. That is the job of the voltage regulator. As the name implies, it regulates the voltage going to the battery. It does this by turning current to the field (stator) terminal of the alternator on and off. If the battery voltage goes below 13.5 volts, the voltage regulator sends current to the field terminal and allows the alternator to start charging. Current will then flow into the battery and bring it up to full charge. If the voltage goes above 14.5 volts, the voltage regulator shuts off the current to the field terminal and keeps the battery from overcharging and cooking itself. This is how the voltage regulator controls the alternator output.

When you first start your car, the alternator needs some current to start working. The voltage regulator supplies this current to the field (stator) terminal of the alternator to get it started.

So far, all we have talked about is voltage. Now we'll discuss the amperage output of the alternator. The state of charge of the battery controls amperage output. When the battery has a full charge, the electro-motive force of the voltage lowers the amperage to almost zero. As the battery charge wears down, the electro-motive force is not enough to stop the amperage, so it flows into the battery and charges it again.

As you use more electrical accessories, such as lights, heater etc., the electro-motive force decreases and more amperage flows into the battery to compensate for the added load. It is extremely important that when alternator efficiency is checked, both voltage and amperage outputs are checked. Each alternator has a rated amperage output depending on the electrical requirements of the vehicle.

In modern alternators, the voltage regulator and diode pack are inside the alternator and are not serviceable by most DIY's and mechanics.

If any one of these parts goes bad, the whole alternator assembly needs to be replaced.

Testing the alternator is simple and basic. You need to check the voltage and amperage output. The voltage is easy enough to check with a voltmeter. If the voltage is between 13.5 and 14.5, it's a good bet the alternator is good. To check the amperage output, you'll need some special equipment. You'll need an ammeter and a load tester to check the amperage.

When the alternator is load tested, a simulated load, usually ½ the Cold Cranking Amperage rating of the battery is applied to the charging system. Then the engine is run at 2200 to 2500 rpm and the amperage is read on the ammeter. The reading should be close to or at the rated amperage of the alternator. If it is, then it's good. If it's substantially lower, then it is weak and should be replaced.

There are some signs you can look for that will indicate a problem with the charging system. If the headlights brighten or the blower motor picks up speed when you rev the engine, you may have a weak battery. This indicates the battery may not be holding enough current to run the car and is working off the alternator. If the charge light is on dimly at idle, this could indicate a weak alternator. If all the warning lights come on while driving, this could indicate a bad diode pack in the alternator. It may or may not still be charging, but you don't know unless you have it checked. At any rate, it will need to be replaced.

If you notice a strong sulfur smell, it could indicate a bad voltage regulator. The battery acid boiling inside the battery is causing the smell. This could lead to a battery explosion so be very careful when checking it.

Today's charging systems have come a long way and are very reliable. A new alternator can last seven to ten years and a rebuilt alternator can last five or more years. It's a good idea to have the system checked when you have the car serviced at every 30,000 miles to make sure it is in good shape and it will greatly reduce your chances of getting stuck with a dead battery.

http://autorepair.about.com/cs/electrical/a/aa122700a_2.htm

 

[Prodigyman]

DGajre777 great post and just what I was looking for.

Thx

 

[Captain D]

I had an optima red top battery blow up while I was on the interstate. I was cruising along and I got a high voltage warning on my radar detector. I waited until the next exit to pull off the highway. I got to the stoplight on the exit ramp and the car died and steam was coming out from under the hood. I thought this is great, I've got a broken radiator hose in addition to an electrical problem. I opened the hood and the radiator hoses were fine but the battery vents were blowing out steam like miniature volcanoes. It took a few hours for the battery to cool down enough so that I could touch it. I don't know if it was a bad alternator that took out the battery or a bad battery that took out the alternator. In any event I lost both the alternator and battery.

 

[kergilman]

I had an optima red top battery blow up while I was on the interstate. I was cruising along and I got a high voltage warning on my radar detector. I waited until the next exit to pull off the highway. I got to the stoplight on the exit ramp and the car died and steam was coming out from under the hood. I thought this is great, I've got a broken radiator hose in addition to an electrical problem. I opened the hood and the radiator hoses were fine but the battery vents were blowing out steam like miniature volcanoes. It took a few hours for the battery to cool down enough so that I could touch it. I don't know if it was a bad alternator that took out the battery or a bad battery that took out the alternator. In any event I lost both the alternator and battery.

Great brake-down story! I went throught this exact same thing last week except I had just installed a new alternator w/o charging the battery first. Got on the freeway, BATT light came on, TT display was reading 15.9v!, the battery blew acid all over, car dies and rolls to a stop. My suprise to find that the voltage regulator in my 99 GS in in my ECU, not the alternator and will not charge above 13.4v so now I am shopping for a used ECU...