Will a Weak Battery Kill a Good Alternator?

[John Ramsey]

I have a 1997 Integra LS and the battery that I currently have is 7 years old. It still starts the car normally every morning, but I know that it is a very weak battery. The other day, I wound up on the side of the road. 35 minutes later the battery was so flat that that the 4 way flashers wouldn’t work. (In fairness to the battery, I did try some to restart the car after it died and when I stopped it was raining so I’d been driving with the blower motor, windshield wipers, headlights, and radio; but those were all shut off when the engine died.)

The real crux of the question is whether I need to replace the battery now, or can I put it off until winter. Because right now, the car is starting fine and I won’t have cold weather to contend with until October. Alternatively, I’ve heard that a weak battery can put an excessive load on the alternator and kill it.

My take is that the battery doesn’t have a cell out, but just lacks the ability to hold anything much more than a surface charge. If this is the case, then why would my alternator care? It gets the battery up to 13.2-4 volts and then says that it’s done with the charge and relaxes right?

Please clarify,

Thanks

Topic

[Joeseph Mama]

I believe that in general a battery does not necessarily kill an alternator. If a battery is low on charge, the higher voltage output (around 14v) will charge the 12.6 volts your battery is supposed to have. Therefore, an uncharged battery is nothing more than an additional load on the alternator when below 12.6 volts.

An older battery will start to sulphate and acquire the ability to retain a much higher voltage which dissipates quickly (surface charge.) An easy way to tell if your battery is getting old is to see if it has a surface charge higher than 13v.

What is hard on an alternator though, is charging a battery that has been depleted entirely; the alternator is then put under a tremendous load for a long period of time. In these cases, it’s important to use a battery charger and not the car’s alternator.

In summary, I believe it is a battery that has no charge that will kill an alternator as opposed to a battery that cannot hold a charge.

[Wayne]

This is what sounds like a case of the battery not holding much of a charge anymore. A weakly “charged” but still relatively good condition battery is the issue for sometimes killing an otherwise good alternator. In other words, to me, your fine, just so long as your aware the battery isn’t exactly a very deep reservoir of power currently.

Alternators in modern production vehicles are there to replenish the average discharge, if taxed with an undercharged battery, creating a large load demand, especially multiple times, this will toast the alternator quickly as it’s not really designed/made for it.

[college man]

A battery and alternator must work in concert. if the battery is weak
it will over work the alternator. If the alternator has a problem it will
affect the battery from being charged.

[Pat61]

I would get a new battery. Two things are fatal to batteries: extreme cold and extreme heat. Heat also effects alternators just as it does any sensitive electrical component. Too much heat and something has to give …maybe a diode. Anyway, spring for a battery and be done with it.

[Lorrin Barth]

Walking is good exercise.

[Author]

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