As reported before, I have been looking at designing a microcontroller based alternator regulator. I am doing this to address some of the limitations of most ‘smart’ alternator regulators on the market. The two primary goals I am looking to achieve, which I cannot source at a reasonable cost (under $1,000) using current offerings, are:
- Maximize generator output at all points of recharging cycle.
- Adjust generator output to accommodate additional engine load of watermaker high pressure pump.
Today when the house battery is being charged the Kubota EA300/DC generator might start at 13.2v and slowly rise over time until capped at 14.4v. During this time we are delivering around 110A to the battery; anymore and the Kubota starts to show signs of being overloaded. But there is a devil in the detail here! While charging the greatest load on the Kubota will be at that point when the voltage just reaches 14.4v. Right when the 'charging' changes from Bulk Charge mode to Absorption Charge mode. In our case 1,584 watts of energy (or 2.12 HP) is being delivered. Given the ‘approx 50%’ efficiency of alternators, delivering 2.12Hp means we are extracting a bit under the 5HP continuous limit of the Kubota EA300.
In order to fully accomplish goal #1 the controller needs to actively manage energy produced (Watts in this case) and hence needs to sample both Amperage and Voltage. Goal #2 requires the controller to recognize when the watermaker pump is engaged and further reduce the overall energy produced by the alternator. All but a few regulators on the market today manage only Volts and rely on the self-limiting factor of the alternator to manage (limit) Amps. Some more advanced ones will have a crude Amp Management capability, but in every case (under $1000) these are all open-looped and very imprecise and unreliable.
Plus I get to play around with controlling computers again! What fun! (sorry, Nerd is showing again)
The design goals for this intelligent regulator:
- Alternator Voltage Regulation (Classic ‘regulator’ function)
- Alternator Amp Regulation (adjust Amps relative to Volts to maximize energy production)
- Reduced Watts produced during watermaker operation (Today I have to turn off the alternator all together while making water)
- Soft-start logic
- Battery Temperature compensation
- Alternator Temperature Monitoring
- Kubota Temperature Monitoring
- Exhaust Temperature Monitoring (Exhaust Mixer)
- Low-Oil Pressure monitoring
- Shut-down and alarm on faulting of any of the above
Optional 2 (Feature Creep)
- Kubota start / stop control
- Kubota Throttle (speed) control
- Maximize Watts produced in response to motor RPMs (Allows for slower / quieter motor RPMs with reduced output)
Stretch Goal (Getting Wide here!)
- Remote Monitoring and Control Panel
- Simple ‘Generate’ / ‘Make Water’ on/off controls.
- Optional auto-start? (Including Time block-outs, and Safety interlocks for motor servicing)
- Good ESD protection
- Watch-dog function to auto-restart if controller faults
- Energy efficient design: High efficiency switching DC-Dc converters, Power Down modes
- Fail-Safe modes (ala, Over-voltage shut down, etc..)
The basics: Am looking to use the Arduino Uno microcontroller board and development environment. Am using KiCad software for schematic capture and PCB layout. Looking to use a used automobile ‘Cruise Control’ motor to give me throttle control on the Kubota. I2C devices will monitor temperature, as well as provide connection to the remote panel.
Will I ever build it? Who knows. But I sure am having fun playing with it. Have many of the key components picked out, the schematic perhaps 80% completed. I do need to find some place to open a Arduino Project and document all this, as this Blog is not really an effective vehicle. If anyone has some ideas, pass them on! And if anyone wants to help play with this, drop me a note.