Friday, May 8, 2020


Last Revised June 20, 2013

After I completed the Arduino based integrated Small Engine Controller and Alternator Regulator some people expressed interest in a standalone regulator only version.  So I started a designed leveraging the work done on the fully integrated project ( See for the full project which not only regulates the alternator, but provides full integration with the engine and its control - starting, monitoring, speed control, remote display, etc..)

Why do this when there are many existing external regulators already on the market?  Simple:  a chronic issue with existing Volts Only ‘smart’ regulators is they will often under-charge batteries - switching out of Acceptance phase way to early.  And the problem is repeated undercharging will dramatic shortening the life of your expensive battery bank.   The reason for this is simple:  Voltage Only regulators have no idea when the battery has completed its acceptance phase and instead use some pre-determined time period - as opposed to the actually needs of the battery. This became such a problem for me on Viking Star that is removed the fancy 3-stage regulator and installed a simple fixed voltage Truck regulator many years ago.  It works well, though on long trips I need to manually adjust it so as to not overcharge the batteries.

However - by retaining the core ability to monitor Amps as well as Volts this regulator is able to monitor the actual needs of the battery, and exit acceptance charge state when the battery shows it is fully charged.  A much better solution that will not only prevent overcharging, but also eliminate the massive damage to the house battery that results from repeated undercharging via a volts only ‘smart’ regulator.

Of course, this project also retains the ability to limit the amount of load placed on the engine by monitoring Watts and if you are looking to develop a small engine based DC generator without the complexities of the fully integrated project, this might be right for you!

A couple of other special features, some of which may make their way back into the fully integrated controller project include:

  • Improved FET driver circuit, allowing support to P or N type alternators from 12v to 48v without any hardware changes or stuffing options.
  • Integrated Bluetooth module to allow reporting and configuration via an external PC, or Smart Phone (using an app to be written)
  • Simple DIP Switch settings for selection of predefined charge profiles and battery size, plus
  • Ability modify charge profiles and other configurations via Bluetooth without needing to recompile the firmware - changes are storied in EEPROM for future use!

The initial set of 3 PCBs has been ordered, and the firmware written in anticipation of hardware.  Over the summer I will be proofing this design and improving the hardware / firmware, and another person will be writing applications to take advantage of the Bluetooth connection, I hope to get support for a wide range of platforms, ala PCs, Macs, iPhones, Androids??   And of course there is an expansion port; future enhancements might include some support the NMEA-2000...


  1. Have you gone back to the future?

  2. Hi, I have a large lithium battery bank and am not happy with conventional regulator options. Your arduino based solution is very interesting and I keep a rasp pi and arduino on board. Do. Have you made any progess with your n2k interface? Nema0183 might be easier. Do you have any for sale?

    1. Rick, hello. I am so sorry I did not see this comment post sooner. Hope you have had some better luck with your Li battery bank, there are now several people using this regulator with their LiFeP04 type batteries - with good results.

      I do have blank PCBs, and have made some progress on a simple NMEA-2000 bridge - (Click on the NMEA-2000 label link at the top right). There is more to come, do drop me an Email @ if you wish to talk more!

  3. Hello,
    Where do I find the schematic, pub layouts and the source code?
    Thanks in advance,

    1. Hello. All those are under the resource tabs at the top of the bog. See the boxes "Links to files" and the associated tabs.