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Dead Battery Kills Alternator

My 2004 Hyundai Elantra gt had to be pushed to the shop over the weekend. To make a very long story short, the mechanic ran an electronic test and said the battery was dead. He changed the battery and 24 hours later the car is having the same problem. Now he tells me the alternator is dead.
He says the alternator died by trying to charge the dead battery. Is this really possible?

I would expect the charging circuito not allow the alternator to be harmed.
Also a dead battery does not present a “short” to the alternator.
I suspect something else. But I don’t know.

Yes, this is not an unusual situation.
Alternators are designed to replenish the current used for operating the starter and the accessories, but when called upon to keep a dying battery charged, this can overburden the alternator.

This is one of the reasons why trying to wring the last bit of life out of a battery can be false economy in the long run. An alternator can definitely be killed by having to constantly recharge a battery that no longer has any reserve capacity. Once my battery is more than 4 years old, I get a load test performed at least once a year in order to assess the condition of the battery.

Yes, you can kill an alternator trying to recharge a deal battery. Not unusual at all.

I agree with the last 2 comments. You can kill an alternator with a dead or weak battery. It happens all the time.

A dead battery can short out an alternator.
One of the ways a battery can fail is the debris that flakes off the cell plates, during normal use, builds up at the bottom and shorts two adjacent cells. Alternators don’t last long if that happens.

Dead battery puts a heavy load on the alternator and can kill it. A good shop would have tested the charging circuit when they replaced the battery but apparently this shop didn’t do that.

I had a 10 month old battery fail on a 1995 Dodge Dakota. I got a jump and decided to head over to my trusted mechanic a mile away instead of continuing to work.

According to the mechanic, driving to work and back (~210 miles), would have damaged the alternator and the PCM. This repair would have been considerably more expensive than replacing a battery.

Two years ago I replaced the alterator on a 1993 Chevrolet Caprice. I bought a rebuilt unit from a local shop with a good rep. The owner recommended I replace the battery at the same time (battery was ~7 years old) for the same reason. I didn’t replace the battery, but I use a Battery Tender to maintain a full charge (12.6V) between drives.

Ed B.

This is the warning that comes with every remanufactured alternator that I install.