Can a bad battery kill your alternator?

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asked Dec 9, 2019 in Repairs/Maintenance by xylitol321 (310 points)
Can a bad battery kill your alternator?

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answered Dec 10, 2019 by Grahlu (51,270 points)
If the battery is bad and not charging up then the additional load on the alternator to provide power to the cars electrical system could cause the alternator to fail prematurely.

Or if the battery contains a short in it then the bad battery that has a short or bad cell in it could lead to alternator failure.

But most times a bad battery will not cause any harm to your alternator.

But even then the battery should be replaced and ideally a cars battery should be replaced every 5 years before it leaves you stranded.

An alternator that is not charging usually doesn't make any noise unless the bearings in the alternator are going out.

If the alternator is just not charging or producing enough voltage or any voltage then you may notice things such as dim headlights, engine sputtering, dead battery etc.

If the alternator bearings are going out you might hear a screeching noise or grinding noise coming from under the hood.

If the bearing go completely out on the alternator then the belt will break and you'll be stranded so get it replaced before that happens.

If your cars alternator is putting out some voltage and working partially then yes the car will still run with the bad alternator.

However the alternator may be putting out just enough voltage for your car to run and not charge the battery though.

So if your alternator is not charging enough then your battery could be dead and you'd need a jump start of the battery to get started again.

If your alternator is not charging at all then the car will run with the bad alternator but only until the battery is depleted of it's charge.

Once the battery is discharged enough then the engine will likely shut off.

You can disconnect the positive battery cable while the car is running and if it still runs then the alternator is okay but if the engine dies then the alternator is bad and needs replaced.

An alternator should be putting out a minimum of 12 volts but ideally 14 volts is what the alternator in good shape should put out.

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