Solar Power Manager Support

Hi Guys,

I recently purchased a solar power manager, specifically: https://core-electronics.com.au/sunflower-solar-power-manager-9v-12v-18v.html

I also purchased a 20,000mAH lipo battery to go along with it, specifically: https://core-electronics.com.au/3-pin-lipo-battery-for-pijuice-20000mah.html

I also purchased a 20W solar panel: Solar Panel 20W-12V Mono 440x350x25mm series 4a SPM040201200

I have a few questions I was hoping you could answer based on my application.

  1. When using the 20W solar panel above with the solar power manager, do I set the MPPT set ‘bit’ to 12v?
  2. The lipo battery I purchased is 3pin rather than 2 pin, so when cutting the wires I technically only have positive and negative terminal blocks to plug the battery into. From my understanding the yellow wire is designed for monitoring temperature, is there any way I can still use this functionality?
  3. If there is no way to use this functionality, is there anything inbuilt in the 20,000mAH LiPo that will detect overheating? From my understanding there is only under and overcharge detection.

My application is that I want the power to run 24/7 to allow my Pi Zero to run from the 5V 1.5A USB output or terminal block output. I also just always want it to charge the battery when there is sun.

With the heat sink installed do you believe I could get 1 year constant usage out of this?

Thanks heaps

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Hi Samuil,

I dont have any experience using the Sunflower board but from my reading the documentation the MPPT to 12V as that is the nominal panel voltage.
Certainly, the sunflower itself doesnt have an input but you could use a microcontroller to monitor the temperature and respond appropriately.
Unfortunately not, the PCB’s on the batteries only just stop it from over and undercharging at the very extreme. If you take a look at the PCM datasheet it is rated at 4.3 and 2.5V respectively which is very far off the desired voltage of a LiPo and will significantly/catastrophically decrease its life.
A whole BMS would be needed to ensure that it is charged 100% correctly taking into account thermal effects.

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Hi Liam,

Thank you for the detailed response.

The solar panel states 12V however it states in the specification that the maximum PV is 18.5V. Will the solar charge control act as a DC-DC converter stepping down the voltage to 12?

Will it need to be a microcontroller to monitor the temperate or is there a temperature sensor that could do this instead? I am assuming a Pico or Aruino could do the job though?

I have tried researching BMS for LiPo however have not had much luck. Would you be able to point me in the right direction for this?

Once again I really appreciate your help.

Kind regards,
Sam

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Hi Sam,

I’ve had a look at the Sunflower board and the panel you have chosen to pair it with. There is more detailed information available here:
https://wiki.dfrobot.com/Solar_Power_Manager_SKU__DFR0535

Your solar panel has an operating voltage range of 0 - 22.6 Volts and maximum power output at 18.5 Volts. I suspect it is listed with 12 Volts in the name for marketing reasons to identify it as portable and caravan friendly instead of a rooftop solar kind of product.

The sunflower module is basically just a buck converter with some clever add-ons and it can change its impedance to suit the input device, so the MPPT setting should be set to 18 Volts.

This sunflower unit does include a BMS, there is a similar DFRobot unit that does not so Liam may have mistaken it for that model.
The battery protection circuit integrated into the LiPo battery (which Liam referred to ) is usually enough to stop them from being drained dead flat to an un-rechargable state, but the under-voltage protection is set quite low so the longevity of your battery’s lifecycle is not well protected.

The sunflower board is not designed to work with a 3pin LiPo which includes an NTC (for temperature monitoring), so it will monitor the battery voltage, but cannot monitor the battery temperature.
The LiPo does include an NTC for monitoring temperature externally, so the integrated protection board does not have a temperature cutoff, for that you would need an external device like a microcontroller to monitor the temperature.

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