Wednesday, September 24, 2014

Outlining the goals.

There are already in existence low cost solar MPPT controllers - some under $100 that were not available even two years ago.  So why do this project?

Like most of the other battery oriented projects I have done - because I want to.   But perhaps a bit more, this will be part of a larger system of battery oriented charging management projects - ones that communicate with each other to improve battery safety and performance, as well as simplify installation.  Some of the high level goals for this project can be outlined as:

  • Sized to match one common large solar panel (240-300w) to a 12v or 24v battery system
    • Current carrying speced at 25A
    • Optionally support 2 panels in series in 24v systems.
    • 48v support by ???  (current design does support 48v battery systems)
  • Modular systems approach:  
    • Multiple panel/controller pairs can be placed in parallel
    • Controllers will intelligently communicate with each other to coordinate charging
  • Simple to use DIP switches for out of the box installs.
  • Available ASCII commands to enable advanced options 
  • Integrate into CAN based battery charging / management system.
As with the other projects, this one will be open sourced for non-commercial use.  All CAD files and source code will be posted under the links above.  And as before the Arduino IDE will be used to make things a bit simpler to use and modify as people with.  (Update November 2014:  Am needing to review the Arduino IDE some - integrating the ATmegaxxM1 uC into it is not that simple..)


A bit more:   Am looking to make a Buck based solar MPPT controller.  This matches up well with common solar panel outputs, as illustrated here:

Example 240W solar panel

The optimal panel voltage in all light levels is around 30v.  This matches up well with a Buck type switching power supply for 12v systems, but could be a bit on the edge for 24v systems - care will be needed at the point where Vpanel and close to Vbat.  And some consideration should be made for a pass-though mode if appropriate.

For simple deployments, a single controller might be sufficient.  But I intend to include a CAN bus to allow communication with other controllers, as well as the SmartBMS project to gain more precise battery voltage and other needs.  This should not only improve battery safety and life, but also reduce wiring by just using CAT-5 cables to connect up all the devices.  (Plus power cables!)

Am just starting on this project, and working in parallel with the BMS project:

More come, as am just getting started....

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