alternator regulation

I have in mind to use the arduino to regulate the voltage output of the alternator in a vehicle. I will be using the arduino Mega board.
I could just use the internal regulator, or the factory external regulator, but they just don't do the kind of things I want them to do.
I want to disconnect the alternator from the vehicle (possibly including ground), increase the output voltage and do some welding with the alternator. I read an article about PID regulating systems, but forgot where it was.
I know I will need appropriate devices to interface with the alternator (voltage dividers, transistors, input protection, etc).
Then there are the endless possibilities of what else I can do with the arduino mega on a vehicle. I already have preparations to use it as an electric fan controller (two speed taurus fan).

Sounds neat.. (or where you trying to ask a question?)

Well I wanted to get an idea of what kind of software you guys would use to accomplish this. I am pretty fluent in C/C++ (from which I gather the arduino language is based on) so writing code for this wouldn't be a problem. I was wondering what kind of algorithm would work well for this.

You're really just going to be monitoring the output level and acting upon it if one or more defined thresholds is passed. You could define multiple voltage levels so that you can do different things depending on other circumstances. If you can also monitor the speed of the alternator and/or the load, you may be able to put a little more intelligence into the control system.

I am very interested in your project as my current project is similar. The software to me (in this case) is the easy part, so I'll be glad to help where I can. But I have not been able to design the circuitry to manipulate the alternator's output from the Arduino. The problem in every design so far has been the control output voltage relative to "ground". Since most switching components do so on the low side, this has so far gotten the best of my electronics skills. I haven't tried designing a high-side control system yet. So I'm not sure what I'll come up against there. It's also important that I mention that I'm trying to use switch-mode regulation on mine for efficiency, rather than linear regulation because the alternator is being driven by a human on a bicycle.

I go into Baja a few times a year and would like to build an alternator based welder too. Will you be posting progress here or in a blog somewhere?

I plan on posting results on my website www.doors-software.com. My current plan is to use the ready-welder (spool gun for mig welding). When it is ready, you should be able to stick weld with it, but I don't know a whole lot about welding.

does anyone know of someone successfully running an arduino based alternator regulator? I would very much like to talk to them...especially if it was setup to data log.

By using the brakelight switch it would be simple to work in a brake regen scheme as well. The alternator wouldn't be under load during acceleration, at least for a minute or two, enough time to either get up the speed or stop at the next light.

It does seem to be some simple logic based on voltage points and switch input. A temperature probe on the alternator case would provide protection for the alternator regardless of it's size...just cut the alternator load 50% if the temperature is above 225F.