Can Alternator Failure Damage Battery?

it could have been undercharging the battery

If it drained the battery down to the point where the car stopped running, it may or may not have damaged the battery. Well, scratch that

- it did damage the battery. question is, how much? Only way to know is to charge it back up (with a battery charger, not the alternator) and then see if it holds enough charge to reliably start the car.

If this car is one of those "has to start every time, every day" deals, I'd replace the battery. It's cheaper than not making an important meeting because you rolled the dice and lost.

good luck,

nate

Note that the Die Hard Gold has some extenisve warranty on it where they will refund you the value of the lifetime left in the battery. If you have only had it for a month, and you have damaged it, you should be able to get almost a complete warranty.

--scott

Thanks for the replys folks. they are replacing the battery . Based on your comments I am asking for the old one to take back to sears. Thanks.

Hard to say, without more information... The battery might have suffered an open cell,or a short circuit, which could have had no relationship to the alternator.

The alternator may have been damaged or may have suffered a failure which lead to the downfall of the battery.

The only thing you can do is have the battery replaced under warranty, and deal with the alternator problem. If the dealer tries to hump you, go to a good starter/alternator shop for repairs, or get a first class rebuild or new alternator from a quality supply store.

Dealers are not always experts, nor are they always reasonable in prices. Choose carefully.

And how does the dealer know that it wasn't a bad battery that ruined the alternator? I've heard that story before too.

Overcharging is what damages batteries. A failure mode of an alternator that results in overcharging is rare. However, some voltage regulators reside inside alternators. Thus a failure of the regulator could be viewed as an alternator failure with those style alternator/regulators. Did the dealer say what exactly failed on the alternator?