I've been having an issue with an '03 Toyota Echo. The alternator died (at least that is what I thought) as the battery kept going flat. I found an alternator at a wrecker and fitted it, and I replaced the battery with a new one. Over the past month the battery has completely died again. It's over a year old now, but I'm getting concerned there could be a problem with the voltage regulator causing batteries to overcharge and boil dry.
I've tested it today with a known good battery that was charged up. I drove it for close to an hour just to give it a chance to put some charge in if it needed to and then checked it with a meter. It was still reading 14 volts as though it was still trying to charge.
I am not really much of an electrician so maybe I'm missing something. Once fully charged, shouldn't the alternator stop providing a higher voltage? If it is constantly charging would that kill a battery?