Who would like to beta test one of my new voltage regulators?
The board I'm using is similar to the one from this thread where I tore down an off the shelf regulator:
Alternator voltage regulator teardown and analysis
However, I've added back in the temperature compensation and added a trim pot to adjust voltage. I'm using a Nippondenso alternator with around 3-5 ohms field coil resistance. A previous design I tried used a microcontroller but it was running a bang-bang output with no deadband other than its ADC resolution, which was a big mistake.
Running a FET in the linear region might give you a very accurate voltage, but I don't think it's worth the elevated temperatures. Especially since the temperature sensor is inside the regulator since installing an external battery temperature sensor is way more complexity than most installers would want to deal with, for fairly little gain. If I were going to add an external sensor, it would be some sort of battery current meter. But I'd rather get a solid basic one working first.