5v mini solar charger

Support
21

Thanks Bob, you may be correct!
I got a bit bamboozled with the description. Perhaps if Jim is online he might enlighten us? Whether the 3.7 battery is an integral component of the Sunflower regulator (or optional feature)?
Either way quite an economical experiment I’ve ordered this unit + the small panel (170mA) linked by Owen and I’ve got heaps of the 3.7V 18650 batteries so we’ll give it a try (for a grand cost of $23).
If the 3.7v battery (2100mA) does the job that’s great but it only gives me about 5 days failsafe whereas a 20,000mA power bank gives me about 45 days failsafe.

Thanks All
Michael

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22

I think the 3.7V battery has to be there. I haven’t got the text in front of me at the moment but I think the charging voltage to this battery is max 4.2V.
One thing you could well try. See if you have any 5V output with about 5 or 6 V injected into the “solar” input with no 3.7V battery connected. This will determine if this unit is a stand alone power bank or not.
If it does provide the 5V you may be well able to charge your existing power bank but please consider efficiencies. I saw somewhere a figure of 73%. Now I don’t know what configuration this refers to but 73% if 170mA = 124mA. If your power bank is say 80% efficient this will leave you with 80% of 124 = 99mA to keep your phone charged. This is assuming your 5hrs of full sun every day.
I hope you can see where I am going with all of this. It is my experience and my practice to always err on the high side and consider worst case. I have found less trouble that way.
I would be very interested in what you find and come up with here. Please keep in touch. These DFRobot units are quite inexpensive so I might get one and have a play.
Cheers Bob

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23

Wise words, thanks again Bob.
Perhaps I could squeeze two of the 170mA panels in parallel into the case. That may give it a fighting chance.
Regards
Michael

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24

On reflection the Sunflower will not do what you want. It requires a connected LIPO battery. (tested just now)
Some time ago, when I was looking at charging my LiPo’s via the sun. I was disappointed in the performance of https://core-electronics.com.au/solar-lipo-charger-3-7v.html and https://core-electronics.com.au/1w-solar-panel-80x100-seeed-studio.html and bought the Sunflower as an alternative. I did some initially confidence testing but have not touched it since. Your post has awakened my interest.

When I read about charging power banks there seems to be a minimum current they require, 200mA was mentioned in one post. LiPo’s can definitely charge with less. The 2 items linked above seems to work initially with a LiPo but after a few hours of indirect sunlight I came to the conclusion the battery was not charging. The setup was not in direct sunlight because it had become way too hot when it was. (LiPo batteries can explode if hotter than 50 degrees Celsius; reports of power banks catching fire when left in the direct sunlight in a car).

Measuring the voltage from the solar panel, the charger and the battery showed the generated voltage was not enough to make the charger work.

Apologies for my previous post about the Sunflower. Think it is meant as a battery charger with solar option. Which is what I was looking for.

Regards
Jim

PS btw the power capacity of power banks is related to the 3.7V lithium inside the device not the 5V it supplies through the USB socket. So actual power available at 5V will be less.

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25

Thanks James for the input.
Drat that’s a shame though… looks like the only sound option for us is to use a larger panel and somehow flood protect it. I can easily run the cabling into my waterproof device case via a cable gland.
Thanks again
Michael

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26

The solar panel I linked above produces 184mA direct facing the sun, 160mA at an angle and much lower if in the shade. I have it attempting to charge a 1100mAH LiPo with the Sunflower.
I had a Charger doctor plugged into the USB out port to check the volts, most likely the LED on that was taking all the charge. The LiPo has remained at 3.9V over the last hour. Removed the charge doctor and will see how it goes.

So the panel does what it is supposed to do. 170mA but in direct sunlight, slight variation and it drops.
Probably my test with the DFR charger was flawed due to panel being in shade. Still the issue of heat from the sun.

Regards
Jim

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27

Worth thinking about. I was about to ask if there was any reason the panel could not be mounted remotely. Like above flood level. I am pretty sure that the panels themselves are waterproof with regards to rain etc (after all most are on roofs) but not sure how they handle being submerged. Might be OK though as rain can be pretty intrusive. Mounted remotely above flood level may be easier to get it pointed in the optimal direction and elevation.
Cheers Bob

28

Thanks Jim
Will be very grateful and interested to learn the results. Is the 1100mAH LiPo being charged via the battery 3.7v or solar 5v output channels? (am assuming through the 3.7?).

Would be nice Bob to get the panel way up high but I’m not too good at tree climbing and parrots are very good at chewing unprotected cables… just for fun.

Cheers
Michael

29

Hi Jim
Just curious to know how the LiPo charging went and /if the panel/regulator was successful in raising the charge?

Thanks kindly
Michael

30

Especially the white ones

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31

Hi Michael,
Sorry I have not got back sooner. Modem decided to play up yesterday, ISP sending a new one. Its working for now but no idea for how long.

The way my house faces the sun shines on an ideal spot in the morning but about midday that spot is in shade. I need to better set up where I place the panel, my design will need to change. Previous testing in the shade did not charge the battery. But the testing the other day in the sun gave me confidence again.

When the sun is on the panel it puts out the rated current and the battery charges. Partial or full shade the current drops significantly. I was not able to full charge the battery due to it being in the shade.

Tomorrow I plan to a more exhaustive test. Need to start as soon as the sun hits that area. I will post my results tomorrow around midday. I will use a smaller LiPo, the charge time will be less.

The test will consist of a1W Solar Panel 80x100 (Seeed Studio), the Sunflower unit I linked above and a 120mAH LiPo. The LiPo will be have half charged at start.

Cheers
Jim

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32

Thanks Jim that’s awesome. Sorry to hear about your modem though.

Will stay tuned tomorrow fingers crossed.

Cheers
Michael

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33

Finished a little earlier than I expected, all good.
Well I am impressed with the Sunflower Solar Power Charger. It worked very well. My previous testing had been very basic.

Test Equipment:
120mAH LiPo
2000mAH LiPo
1W Solar Panel 80x100 Seeed Studio
2W Solar Panel 80x180 Seeed Studio
2000mAH Power Bank
Charge Doctor - USB power measurement device, 4 x 7 segment LEDs to indicate Volts and Amps.
2 x Multimeter one for current the other for Voltage

All current measurements are from the solar panel. Panel gets quite warm with full sun on it almost hot.

1W Solar Panel 80x100 Seeed Studio
160mA full sun, shading only 1/4 of panel dropped to 22mA. Cloudy day would be a problem.

2W Solar Panel 80x180 Seeed Studio
280mA full sun, shade also dropped output, but not as much.

Test 1.
120mAH LiPo and 1W Solar Panel Charge Doctor
Sunflower auto switched off when 120mAH fully charged, back on again when Charge Doctor connected to USB out port. Current remained at 99mA while Charge Doctor was plugged in.

Test 2.
120mAH LiPo and 1W Solar Panel and 2000mAH Power Bank
120mAH fully charged. Connected 2000mAH power bank to the USB out port, lights flashed briefly then went out. Expect the 120mAH is being overloaded.

Test 3.
2000mAH LiPo and 2W Solar Panel and 2000mAH Power Bank
Connected LiPo and panel. LiPo was half charged so let it run for about an hour.
Plugged in power bank, lights begin flashing indicating it is charging. Current remained steady.
Checked 45 mins later, panel part in shade, current at 100mA. Power Bank lights still flashing showing it is still charging. Moved panel to full sun, 313mA current. Voltage level on LiPo indicated it was significantly discharged from what it was at the start.

Conclusion:
Sunflower needs a LiPo battery to provide power to the USB out port. It will not provide USB out volts with just a solar panel. When available it will use the current from the Solar Panel to charge the LiPo while still providing a stable USB out voltage. If solar current drops below the USB out demand it will still provide a stable voltage as long as the LiPo has charge. When there is no solar current and the LiPo is discharged it will not power the USB port.

Regards
Jim

Test 3 setup

Test 4
Test 41429×839 211 KB

EDIT: Yeah the file says Test 4 that is a typo.

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34

Thanks Jim!
I’m just off to a first aid course so will attempt to digest after lunch. Sounds promising though!!
The larger 2W panel sounds like the go, combined with bigger LiPo sending power to power bank then device.

Much appreciated
Michael

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35

Some thoughts.
These panels from Seeed Studio are very basic and cheap. I took some pics of the edge, it is not really water proof, over time you would get water ingress. The pics on Core Electronics web site don’t show this very clearly. For my purpose it does not matter as it will only be outside in the sun when charging a battery. If your enclosure is water proof, condesation may be an issue, I know it is with weather stations.

The current drain from the USB out port needs to be less than the current supplied by the panel when in full sun. Some power banks try to use max current to reduce charging time. The one I used is pretty basic and cheap, it does not have a fast charge mode.

Trickle charging a LiPo or power bank may reduce its life. I read that phone batteries last longest if they are used till 30% then charged to at least 80%. Anyway it might not be an issue with what you are doing.

I tried the 2W solar panel with the 120mAH LiPo and the 2000mAH power bank, no success, even with the higher current. The demand from the tiny battery is just too much. Probably the LiPo mAH needs to at least match the power bank mAH From what I have read 200mA seems to be what power banks need to work properly.

Anyway … best of luck
Jim

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36

Thanks Jim
I’ve ordered a couple different types of regulators. Ideally I’d like to go straight into the power bank (no secondary battery).

The 1060 Pelican case with clear lid has correct dimensions to fit the 2W panel:

Thanks so much for your assistance. I’ll post some pics of the prototype.

Cheers
Michael

1 Like
37

Sounds excellent Michael,

If you’d like, you can send a writeup of the project through the link below. If it gets added to the site here you will be rewarded a store credit. Also, feel free to share it on the forum too, we’re excited to see how it turns out.

Bryce
Core Electronics | Support

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38

Hi Michael, Jim.
Has anyone put a load on anything while attempting to charge. Seems to be forgotten there will be a phone attached to all of this while charging. This load has to be added to charging current.
Hypothetical case. I don’t know what the internal phone charger’s efficiency is but assume the phone dc input requires an average of 100mA @ 5V over 24 hr to maintain charge.
Say efficiency of power bank 85%.
Required input to power bank to replenish = (100/85)*100 = 118mA
Assume solar panel/controller directly charging power bank (will have to be at 5V)
Assume charging system efficiency is also 85%
Required input from solar panel FOR 24 hr = (118/85)*100 = 139mA
BUT Solar panel can only output for say max 4 hr and we would need 139mA for 24 hr.
Therefore Solar panel would need to provide about 140 * 6 = 840 mA just to maintain equilibrium assuming the sun shone directly on panel every day. That is virtually no head room.
This of course carries a lot of assumptions not the least being able to directly charge your power bank. This would require you to use a solar controller (MPPT preferably) directly outputting 5V which you may find scarce, I don’t know, I have never tried to source one. If you can’t and you have to charge 3.7V and you insist on using your intermediate power bank you will have to add another layer of something less than 100% efficiency to the above. This may push your solar panel requirement to almost 1A. Remember your total capacity will be the weakest link as everything will be in series.
Michael you are the only one who can measure what your phone requires when operational. Determine what is required in mA/hr total to recharge it after 24hr use, divide by 24 to get your average then slot this into the above modifying efficiencies for known values and see what you come up with. It could be a little more than you think, Particularly if you allow a bit of “Fudge Factor”. Whether you do this or not would depend on how important and reliable you need this to be.
Cheers Bob

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39

Thanks All
To be honest I don’t think I’ll end up using the Sunflower it’s too complicated for the job. I’ll use a simple 5v solar regulator (link below).

Testing should be simple, Firstly I’ll hook the panel directly up to phone (at 10% charge) via regulator and see if the charge goes up by how much and how long it takes. I know the phone uses about 10-15% battery a day so the internal battery (3000mAh) needs to go up at least 10% (300mAh - 450mAh) on an average day. Better if it’s more.

I’ll then do the same with a flat (maybe 1%) power bank inline (between regulator and phone). If the system konks out we know it doesn’t work. If the charge goes up I’ll measure how much (fluctuation) over a couple of days.

Cheers
Michael

All the power bank does (deployed fully charged) is give me some redundancy (30 - 40 days) if the weather is shit.

40

That’s getting to be the right idea. I have been trying to talk you out of using what would amount to using 2 power banks in series. The total would only ever be as good as the smallest. Your panel may be quite big though. You need to have one large enough to give it a chance as I think this device would stop working below 5V.
I can understand why you want your larger power bank to give you some no sun time. Good idea but you still have to replenish it and still keep the phone topped up.
Had a browse through Jaycar catalogue a short time ago and they have a unit which just may do your job. Quoted to be regulated 5V @ 1920 mA in full sun. Does not appear to have built in battery and looks like you could connect to your power bank and then to phone which is what you wanted. A bit larger than your original requirement at 325 x 255 fully deployed but you may have to live with that. Physics takes over here and I really think you are going to look at bigger than your original idea to avoid disappointment in large chunks.
Jaycar cat no is MB3595. I think it would be worth a visit to have a look and talk to them.
Cheers and let us know how you get on. Interested.
Bob

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