Sunflower: Solar Power Manager 9V/12V/18V (DFR0535)

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DFRobot is launching a brand new series - Sunflower, focusing on high-efficiency, small power solar energy management for IoT projects and renewable energy applications. … read more

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Is it possible to find the weight of these two solar power managers. My project requires minimal weight (aerial craft) and will use 9V thin film solar panels . Thank you.

I intend to buy the DFR0559. Would have been on my last order ‘with a short delay’, but I needed to other stuff quickly. So next order. It is just what I want and cheap. Solar charger, USB charger, USB out. Kool.

This product looks good if you need higher voltages and current.

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Hi Bruce,

This product is about 62 grams all together. This includes the accessories in the package. Very cool project! I’d love to get an update once you get it flying!

Thanks Steve,

A little on the heavy side, have a payload of 200grams. Ill use it in
the development stage and keep looking for a lighter product.


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Received DFR0559 today. Weight is 12g. But it is only 5V.
I you want to reduce weight a custom design is probably what you want, including only what is necessary. There is a lot of extra weight on DFR0559 with all the connectors.


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Thanks Jim,

  Ill keep that in mind for the future however I've ordered one of

your other products for the moment. I had thought about removing
the unwanted connectors but a custom build would be even better.

Thanks again for your personal service, rare in today’s world.


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Hi, I recently purchased this DFRobot solar controller DFR0535 from Core Electronics. My question is how does the short circuit and overcurrent/overtemperature protection operate on say the 5V output? According to the Wiki, it suggests that for a short circuit, the battery protection chip will shut off all outputs due to the inrush current. It then goes to say for outputs 1 and 3, that for overcurrent conditions, the over temperature protection will operate and limit the current (presumably this is built into the MT3608 boost converter).

The issue I have is that I can barely draw 1A at most out of the output, and if I try to increase the load beyond this, it just shuts off all the outputs. I would have thought the 5V output would have been able to output at least 1.5A. My input supply is 24V that is capable of supply up to 5A.

Can you please advise?



Reading the documentation & schematic for the DFR0535 along with the datasheet for the MT3608 leads me to the conclusion the product is designed to be powered by a 3.7V Lithium battery which is then charged by a solar panel. The battery is stepped up to provide 5V & 9/12V outputs.

In your post you say you are using a 24V supply. How are you connecting this to the DFR0535 ??
If you connect just a charged Lithium battery, what current can you get from the USB 5V output ??
If you connect just a 5V USB to the USB input, what current can you get from the USB 5V output ??

Sometimes these kind of circuits need the Lithium battery and solar panel to work correctly.

The specification says 5V 1.5A so I would expect to get that. The datasheet for the MT3608 says 2A, but the graph shows regulation fall off at 900mA and does not show anything beyond 1000mA.

I purchased the DFR0559 (fixed 5V) and can confirm it works with a battery and solar panel and with just a battery or 5V USB input. But, it will not work with just a solar panel. It is also rated at 5V 1A and the solar panel input is 5V only. (the DFR0535 is more flexible but much more expensive).

All the best, regards


Hi Sam, Welcome to the forum :slight_smile:

I think @James46717 might be on the mark here and the problem may be between the interaction of the battery and the input supply.
The product wiki does have some confusing wording but does give some details on how the protection circuits work and their limitations.
I’d agree with your reading of the output protections, using a current limit for output 2 and overtemperature limits for 1 and 3 is a bit crude but I suppose it works.

We’d need to verify what current your battery is capable of delivering and how your input supply is connected. If the input supply is being cutoff then you will only get the maximum power output of the battery, which is limited below 5V and 1.5A output.

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thanks @James46717 and @Trent5487676 . I had the 24V supply plugged into the solar in on the DFR0535.

I did a test as you suggested with and got the following results:

  1. 5V USB to USB input; max current on 5V output was 0.72A before it turned off all outputs; once I dialled back the current (adjustable dc load), the outputs all came good again.

  2. LiPo battery connected on input, max current on 5V output was 0.71A, which turned off all outputs, but for some reason disabled the outputs, even if I decreased the load current. I had to eventually disconnect the battery and reattach, before outputs would start working again (this is pretty strange).

I did noticed that as I approached the max currents as mentioned above, and then touched my finger on the LT3652 chip, it would turn off all the outputs, which I guess is from the thermal folderback protection. Perhaps this is the reason that is causing my outputs to turn off.

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If I had bought this device I would be very disappointed in its performance as you have detailed and would want a refund.

This is worrying. Just touching the chip should not cause it to stop, unless it was a massive static discharge. It leads me to think the chip is operating right on its limits. Is the chip excessively hot when touched ??

Something I neglected in my post. Assume you have the heat sink attached beneath the board ??
As you are using just a DC supply, the MPPT setting should be OFF as described in the Wiki.
The use of 24V supply is at the higher end of the input range, maybe try a lower supply.

A number of other questions come to mind but it is difficult to give an adequate response with out the device in front of me and then to work through all the different combinations. I am tempted to buy one of these to experiment with. If the device is not living up to its claims then the manufacturer should be informed, or the one you have might be faulty.

I am sure Core Electronics would like me to spend some money, LOL. Maybe someone at Core Electronics could investigate this product. Because, based on what you have stated it is definitely not working as it should.



Hi Sam,

As James said, the maximum power of regulators like these are often dependant on heat dissipation,. Even just placing your finger on the chip (if it doesn’t get too hot) can be enough to sink away some of the heat (with a proper heatsink being better).

But if you’re convinced its faulty, get in touch via the email on our contact page, and we’ll go from there.


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I have ordered a Sunflower: Solar Power Manager 9V/12V/18V DFR0535.
In the post below, I used a 20W solar panel and DC to DC regulator to charge batteries; pretty crude way of doing it.

It has been successful but I always considered a better charge / power supply system. I also have a couple of 2000mAH LIPO’s I could use with the Sunflower.
Will post here when it arrives and has been tested. I will also conduct some investigation into the Sunflower and its capabilities and post here too. If it does not produce 1.5A on the 5V output I will contact DFR with a please explain.

The way I will be using it, is as it was designed to be used by DFR.



Hey James and Sam,

(btw Welcome to the forum Sam, thanks for posting :slight_smile:)

Just read through this discussion, this sounds like some highly unusual behaviour, I haven’t had this reported on any Sunflower boards before, but if you’ve found a hardware fault (referring to both @James46717 and @Sam172239 and anyone else noticing this issue) please reply to your order confirmation email and we’ll get the appropriate return/refund/replacement/repair etc. sorted out for you right away to get the project back on track!

We’d be glad to test this one out too if we had any here in the warehouse at the moment. We’ve got some on order which are all already allocated to orders except for one that is arriving here next week on the 8th according to the current estimate, if this post is still open when it arrives we’ll see what we can do in the team here to run into the same issues.

That behaviour does sound quite unusual for one of these boards, and as @James46717 suggested earlier, if the board is getting hot there is quite possibly a hardware issue. I’ve got two questions and a request to help identify the issue here :grinning_face_with_smiling_eyes:

First, when you’ve been measuring the current the board is drawing have you also been using an ammeter or similar setup to determine how much the board is drawing from the power supply you’ve got with it? Should be able to apply Kirchoffs law to determine the inefficiency of the board and determine if any funky business is going on with the IC or traces.

Second, which LiPo are you using? Was it one of ours? If not, what’s the capacity and voltage of the cell? It shouldn’t matter, but I’m interested to see whether there’s any known issues with the protection circuits causing this kind of cutoff behaviour in particular setups.

Finally, could you please send through a photo of your board and the rig you’ve got it set up in? It can be very useful sometimes in ensuring that the pinouts are all correct and that the model matches the version we’re testing.

@James46717 can you please @ me if you’ve got some results from testing your board, I’m curious to see what the issue was on this one. Enjoy your long weekend everyone!


The board I have ordered is most likely in the current order you have. So by the time I get it, you may have been able to test them.
Mine will be going into an active installation and I will be able to test it over time with real world scenarios, not just bench tests. As usual I will do the basic confident tests, which I always do with a new product.

Any results I will post here or in a separate post, I am not expecting any problems. The other Sunflower product I have works very well. But ya never know, haha.


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Thank you all for your feedback, I can see this is a great community to share ideas and support each other.

I think I found out what the issue was. Thanks @James46717 for the tip.

So I tried again, and this time connected both my Lithium battery and 5V USB to USB input with MPPT set to off and was able to draw just shy of 1.5A on the 5V output (using my XY-FZ25 electronic load) before being disconnected. Woohoo!

I would also like to add, that in my previous setup (when having some weird issues with my ZTE Li3711T42P Li-Ion, 3.7V, 1100mAh battery), I decided to replace with a new battery Nokia BL-5C 1020mAh 3.7V. This fixed the issue with not being able to reset the battery protection.

So, in summary I believe this product is behaving as it should, probably just operator error.

Thanks all :stuck_out_tongue_closed_eyes:


Received this board a few days ago. It worked as expected, no problems.

Solar Panel is 20W and LiPO is 2000mAH.
The board will supply power with just Solar or Battery or both. Available current is higher with both; before protection circuit cuts in.

It consumes around 2.7mA with no load. The small LEDs use about 0.5mA each. The 12V circuit draws more quiescent current than the 3.3V & 5V circuits. Suggestion would be to disable the ones you are not using by removing the jumper.

The board produces significant EMI, enough to interfere with an small digital radio, causing it to cut in and out when at higher current levels. Shielding should be considered for a RF application.

I did not test the Solar input with just a power source other than the Solar Panel. It is not designed to be connected this way.

Anyway, an impressive board which I will find very useful.



Hi James

Yes it is. If you read the Wiki on this product it says the solar and USB inputs can be connected at the same time. The USB takes priority. That is when it is connected and powered the solar is disconnected automatically.
Cheers Bob


Hi Bob,

Agree, and this was tested.
Connect a USB charger to the USB IN and the the Solar IN is disconnected. The battery is charged via the USB IN. This is shown in the schematic below. It would allow for USB charging when there has been not much sunlight or no Solar Panel connected.

But, I was referring to the situation where, lets say, a 12V power supply is connected to the Solar IN rather than a Solar Panel. Although this will work is it not the purpose of the Solar IN connection. The LTC5632 is designed keep a solar panel at its maximum power point tracking (MPPT) and provide this energy to charge the battery or to supply to some device. For my 20W Solar Panel this is 17.4V & 1.16A. Testing on the panel has shown this to be correct.


EDIT: The Wiki shows a situation where you can use the Solar IN to charge the battery via an AC adaptor. In this case the MPPT should be turned off.


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