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My multisource battery charger project for small boat

I have battery pack 12V 27Ah (3 x 9Ah) and three electricity sources on my catamaran:

All battery chargers, that I’ve found in internet, can utilize maximum 2 sources: solar panels and windgenerator. Some advanced can brake wind generator by swithing on ballast resistor when battery is fully charged. But no one can utilize three sources with current limitation

I’ve decided to develop my own by using available ready components from Aliexpress

Big thanks to Oleg Timofeev for help in this project.

We discussed multiple variants, including Arduino, current sensors, etc. But we’ve finished on next solution:

That repeated with slightly differences this one:

But I’ve found this publication when project has been finished. :)

Returning back to requrements of the controller:

  • It should utilize max power from all tree sources.
  • It have to have a possibility to adjust maximum of charging current.
  • It should charging from source voltage starting from 7V
  • It have to brake wind generator via shortcut when battery is fully charged.
  • It have to protect battery from a critical discharging.

I’ve selected constant voltage charging method. Device that support it id DC-DC boost controller based on LT3780



On Aliexpress it’s possible to buy for 9 euro with delivering.

I bought two of them. On both I’ve set input voltage to minimum, output voltage 13.6V. On the first one I’ve set output current to maximum, and on second one limited current to 0.1C of battery, that in my case - 3A.

Also I’ve bought two under voltage power off module

First going to work as battery protection. I’ve set turn off voltage 11.6V and turn on 12.0V. And second one going to work as signal of battery full charged state for brake wind generator. I’ve set it for turn off 13.0V and turn on 13.6V.

Signal of second module going to solid state relay XY-MOS. It’s about 6 euro with delivering.

I’ve selected 40CPQ060PBF Schottky diode for my controller




After discussion on forums, controller design was changed to:

Differences: changed charging voltage based of battery manufacture requirements, and added hysteresis module. Now it possible to set voltage gap between stop and restore charging process.
Requirements of this module is under question.