Looking for second opinions or other leads to investigate for a charging problem.
On the return leg of a cross-country trip, the battery in my 2007 Kia Rondo died. I was able to limp to a parts store, where they checked the battery, found it marginal, and replaced it. The battery was three years old. I got back on the road and drove for an hour before the same problem cropped up again. Limped the car off the highway and got it to a service station. After a jump start, the mechanic there put a voltmeter across the battery and checked voltage at idle, under acceleration, and under load (headlights, blower motor, wipers, etc). The voltage started around 13.6 V and dropped rapidly to about 6 V. He diagnosed it as a bad alternator - specifically the voltage regulator within the alternator.
Since I was eager to get home, I found a rebuilt alternator at Carquest and got it for him while he started getting the old one out. He was a little skeptical about a rebuilt alternator, but I couldn’t get a new one quickly enough for my needs.
He put in the new alternator, charged the battery, and re-started the car. Voltage across the battery terminals started at 14.2 V, then dropped gradually to 13.9, 13.6, 12.6, and so on. After a few minutes, it would only get up to 14.0 under hard acceleration. The mechanic declared that the voltage regulator in the remanufactured alternator was also bad, and that this is a common problem with reman alternators.
Was something else wrong to begin with? Is something else frying the regulator?
(I don’t know this mechanic, but I got the chance to talk with a lot of his customers while i hung around his shop waiting on the repair. Numerous loyal return customers who spoke highly of him, including one who said she was his very first customer 35 years ago. He seemed to me honest and knowledgeable.)