Hi Tien
I think the battery (lipo) is just going flat. 240mA out of the solar panel is not very much. It would eventually charge the battery but with the UNO connected the solar panel has to supply enough current to operate it AND charge the battery. Don’t forget the battery will have to be fully charged while the sun is out as the battery has to run the UNO while there is no sun.
240mA would be struggling to operate the UNO without charging the battery at the same time.
Cheers Bob
Hello Robert,
How big the solar panel you reckon should i use? Thanks
Hi Tien
Depends on how much current the load requires.
I would suggest you have a detailed read of the product Wiki here
before you go much further.
Cheers Bob
Yeah. DFRobot tech Support also suggested me to increase the capacity of my solar panel. Just not too sure what the max mAh is available out there with 4.5v to 6v? Don’t want to fry the board!
Hopefully someone has tried before with a solar panel that works well with a lipo using this board.
Shall check out jaycar and altronics this weekend.
Thanks
Hi Tien
It has been a while since I have seen anything on that Sunflower device but I seem to remember there is a Max allowable solar voltage input. You should get that figure from that Wiki. I have an idea the Jaycar and Altronics units will be about nominal 12V (which probably have an open circuit voltage of about 17V) and are targeted to car/caravan use.
Have a look at this Core video for some ideas
How to Build a Solar Powered Raspberry Pi 4 With PiJuice
Cheers Bob
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Hey, I’m looking at getting some of the DF Robot Sunflower: Solar Power Manager 5Vs. Could I use this to charge a 3.7V, 5000mAh Li battery via the screw terminals?
Yes.
The Sunflower has a CN3065 LiPo charger chip.
Note: this chip has a maximum input of 6V so the solar panel must not exceed this voltage.
As @Robert93820 said the solar panels from Jaycar and Altronics are much higher voltages and would destroy the sunflower charger chip.
Cheers
Jim
Hi, does the solar power manager support load sharing?
Is there anything done to prevent the Li ion battery from being constantly trickle-charged by solar? (a known issue when using TP4056 to solar-charge 18650). How is this product better than DIY solution to using TP4056?
That’s a lot of deep questions
I don’t know about load sharing, but the user experience of this device seems to be pretty seamless which implies it handles load sharing gracefully enough.
This will likely be no different if it uses the same BMS chip.
It’s premade and ready to use 
If you have specific needs a custom solution will always be better, but i define ‘better’ here as low-fuss and ready to go.
Hi Michael,
Thanks so much for finding the time to reply.
Since I posted my question, I found the following statement on the product page (Solar_Power_Manager_5V_SKU__DFR0559-DFRobot) :
“Automatic recharge: If the battery is fully charged (DONE ON), the module input source (SOLAR IN) not powered off and the battery voltage decreases due to self-discharge or load, when the battery voltage drops below 4.05V, a new charging cycle will automatically begin.”
So I guess that this circuit is indeed causing trickle charge?
I interpret ‘trickle charging’ to mean constant, low-current charging.
The above spec reads to me as if there is actually voltage-dependent charging - the charging is only active once the cell voltage drops below 4.05V.
Which makes sense, from a battery longevity point of view.
Awesome. That’s what I was hoping for 
Although, I am not sure how they achieved that if the board is using the same BMS…
In any case, I do agree that this is a plug and play solution for most people.
Thanks again for the response!
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The Product/ site Sunflower: Solar Power Manager 5V | Buy in Australia | DFR0559 | DFRobot | Core Electronics
Has a broken link to the Product Wiki,
It should be:
The Prouduct/ Site:
Its More Documents link should be:
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Hey @Elliott254134,
Thanks for picking on that! I have passed this on to our team and we will update those links soon.
All the best.
Sam 
I understand the conversation from April 2023 to mean that the DFR0559 (DFRobot Solar Power manager 5v) :
- automatically connects to one of the Solar Panel or the USB-IN power sources at a time
- primarily supplies power to the USB-OUT from the input source
- if the current input source is insufficient, it is topped up with current from the Li-Po battery
- any excess of power in is used to charge the Li-Po battery
It seems that my solar panel also has a built-in 5v regulator … voltage is either <0.2v or 4.2v to 6v, while the current is rarely enough to do more than slow down the battery drain.
What I am wondering is … is the DFR0559 choosing the input (solar or USB-In) based on higher voltage, and thus ignoring that the powerbank connected to USB-In is fully charged because of nominally lower voltage ?
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Hey @Donald23173,
I have done some testing with this module and one of our staff members’ powerbanks.
The documentation for the Sunflower states that the USB input will be used over the solar input whenever power is detected over this connection. However, it also contains a disclaimer specifically about the automatic shutdown function that a fair amount of power banks use to stop output when a load above a certain threshold isn’t detected.
From our testing and the documentation I would be pretty sure this is what is happening. The Sunflower should always use the USB-in over the Solar-in when power is detected on the USB-in, however, it is likely that your power bank is not detecting a large enough load being placed on it and is cutting off its output because of this.
Hope this helps!
Hi Donald
No. The Solar is disconnected while 5V is available at the USB power input connector. It has nothing to do with which is the higher voltage.
Cheers Bob
Add on: To explain, there is a Mosfet in series with the solar supply. A voltage on the USB connector switches this Mosfet OFF.
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Thank you Samuel and Robert.
This is good news, in that I can place a backup battery on the USB-In, and switch a relay to connect it when required to boost my main battery.
The bad news is that a Powerbank is probably not the best sort of backup battery. I have noticed that sometimes attaching the USB cable starts it charging, but sometimes i also need to press the button on the powerbank (which I won’t be doing in the greenhouse in the middle of a rainy night). More for me to ponder. Or maybe it’s just me confused by trying to switch relays then going into deep_sleep (ie power off the ESP32) and expecting the relays to stay set 
Hi Donald
Been down that path many times. Not going to repeat.
They detect end of charge when the current requirement drops to a preset level and shut down.
One thing I personally have not tried though is to determine if the power bank reconnects automatically when the connected battery becomes depleted or if you have to disconnect and reconnect / push start button.
I strongly suspect that a reconnection / button press is required. I will try to do the experiment to-morrow.
If that is the case it probably will not be suitable for your purpose.
Did we not go down the latching relay path in another post???
Cheers Bob
