Tuesday, April 30, 2013

Alternator Regulator-only???

Now that the Small Engine Controller seems to be working well, I have been playing with this idea of an Arduino based Alternator Regulator - just the regulator with none of the Engine control capability.  Myself, I would use this in the Mains alternator replacing the fixed voltage Truck regulator I put in several years ago - after finding the existing Smart REgulators were not that smart, and would keep dropping into Float mode part way through charging the battery.  I got tired of stopping the boat, turning off the engine and restarting, just so that the 'smart' regulator would actually charge the house battery....

Here is a 3D photo of what I have mocked up so far:

It is sized to fit inside a dual SSR heat-sink.  My idea is to mount the TO-220 packages onto the heatsink, using screw holes in the PCBs to gain access.  Prior calculations show this will be a massive overkill, as the way the FETs are being driven there really is very little switching loss.  But such a heatsink does make a well protected package.

Currently, have the following features in the design:

  • Monitor Volts, Battery temp, and Alternator Temp.  Adjusting as needed.
  • Monitor Amps - allow for precise capacity reduction say for small DC generators, but also gives another way to decide transition between different charging modes (ala, Exit ACCEPTANCE phase when amps reduce to 2% of battery capacity) in addition to time-outs.  Maybe make this optional, as it would require an external amp shunt be installed.
  • 3 stage charging, optional 4th 'overcharge' mode for AGM batteries.
  • Feature-in input - can be used for verity of things: selecting Equalize?  Reduce alternator output?  Other???   It would even be possible to have more than one input into the regulator, via simple resisters.  (It is how I do local switches on the larger engine controller)
  • Feature-out output.  Low driving signal that could be used to drive a ALT lamp when there is a fault?  Or???
  • Configurable to support 12v to 48v systems.
  • Configurable to support P-type alternators (High Drive) in 12v systems.
  • Configurable to support N-type alternators (Low Drive) in 12v - 48v systems.
  • Could drive very high amp alternator, or even more than one?  FETs will support 20A+ of field current.
  • DIp switch, or jumpers for selecting predefined profiles - or custom one.

Changes from the integrated controller would include dropping:
  • All engine control and monitoring functions.  Just an alternator regulator.
  • Switching from one-wire temp senders to 10K NTC ones.  But not decided on this one.  Part of it is I found a source that makes the NTC probes already in a copper sleeve!
  • No remote panel.  (Hum - wonder if a CAN bus would be possible???  That drives NMEA-2000!)
  • High Drive limited to 12v only systems.

Is anyone else interested in something like this?

UPDATE  Summer of 2014:  Did move forward with this project, see full details here:


  1. Is there a way to detect that too much power is being drawn off of the small engine and to slow down how much power is being drawn?

  2. Kyle, Hello. If by 'slowing down how much power is being drawn' you are asking if there is a way to limit the amount of power being drawn from the engine by the Alternator, the answer is Yes. Because I monitor (and regulate) both the Volts AND Amps, I can calculate the Watts, and hence limit the total load being placed on the engine. It was one of the core functions of my integrated controller (regulator and engine controller) - to be able to regulate the watts. I carried that capability over to the stand-alone alternator regulator.

    So, if you have a very large Alternator on a small engine, you can configure a max limit to the number of Amps (and/or Watts) that the regulator will allow the alternator to produce, and hence not overload the small engine.

    Is this what you were asking?

  3. Hi, this is exactly what I am looking for. The regulator on the alternator in our boat died recently and I was looking at designing an Arduino based regulator from scratch but no point in re inventing something that may already work. I am looking at a very basic control with voltage regulation and current limiting for 3 stage charging. Have you done any further developement on this project over the last year??

    1. Wonderful! And yes, have made progress - see here: http://arduinoalternatorregulator.blogspot.com/

      Just completed a group-build, and have some left over PCBs with a few parts mounted. Would be wonderful to have another Arduino-head playing around with this and improving it. Drop me a line with your Email address at mvVikingStar@gmail.com if you are interested in a board!