Using Prop as solar panel MPPT controller via adjustable Switchmode Power Supply

It is very easy to use the Prop as a direct solar panel MPPT controller for a brushed or BLDC motor (for instance a pump). In this case you can use a PWM motor driver or 3phase ESC. There is a lot of voltage and current ripple, so the measurements need filtering and averaging.
In the case of solar panels connected to sensitive sensors and staged battery chargers a much smoother and accurate controller is needed, such as an adjustable switched mode power supply.
I have found that the cheap adjustable switched mode power supply modules on ebay and other online stores are quite efficient and smooth.
The voltage adjustment seems to be universally controlled by a 10K pot.
It is quite simple to remove the 10K pot and solder in a pin header for control by the Prop via a Digital Pot.
In the case of solar panels, a high voltage digital pot is required, for instance MCP41HV51.
Attached is photograph of some modified switched mode power supply modules.

Comments

  • RaymanRayman Posts: 9,556
    edited 2019-05-09 - 16:45:36
    Interesting...

    Could you use this to charge a 12V SLA battery?
    How would this work?
    The pot adjusts the output voltage, right?

    Do you measure the current and voltage from the solar panel and then adjust the pot for MPPT?
    Prop Info and Apps: http://www.rayslogic.com/
  • Rayman,
    Yup, I use the switched mode power to control the incoming solar power to a remote SLA battery system. It could also be used for other battery packs like Li-ion, Li-po with the appropriate charging cycles.
    If you want your batteries to last you need to apply phased charging cycles with accurate voltage and current control, and low voltage cutout.
    I measure voltage and current at the panel and at the battery. I find the INA219 current sensors are quite accurate and measure negative current (battery discharge) fine.
    With an oversized solar panel, MPPT is usually not that important, except at initial bulk charge and low sun. Under these conditions it is easy to pull the solar panel down with too much current.
    The digital pot gives you fine control over the switched mode power supply and the voltage into the battery system.
    The power demand of the battery system is variable.
    The output of the solar panel is also variable as the sun varies with clouds and time.
    By finely controlling the voltage via the digital pot you can manage the panel power and track the panel peak power when required.
    I know there are many battery charging IC's (some with built-in solar MPPT), but I needed a Prop for the system time control and output control anyway, so I figured I would just extend it to battery charging as well.
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