Controller for 5v Solar Panel?

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peejayw

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#306439 23-Jul-2023 10:31

I am wanting to connect a nominal 5v 10w solar panel to a 5v LED reading lamp via a power bank. I say nominal because I am only measuring 4.9v and 0.5a in bright sunlight. The power bank is an Anker Powercore 10000. My question is, do I need any sort of controller between the panel and the power bank to disconnect it when the power bank is fully charged or is this handled within the power bank?

Thanks.

I'm supposed to respect my elders, but it's getting harder and harder for me to find one now.

neb

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#3107364 23-Jul-2023 19:47

The power bank will be able to handle assorted off-spec input since it's using a DC/DC converter to go to/from the internal cells voltage, but even then the solar panel could be giving quite low voltages if it doesn't have its own DC/DC converter. It'll depend on the panel and how cheap&nasty it is, if it's just cell output straight to the connector then you could add another DC/DC converter at that point to go to a consistent 5V.

Also, how are you measuring the voltage and current? What sort of cable are you using between the cells and the power bank?

peejayw

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#3107367 23-Jul-2023 19:59

Thanks, I am using one of those cheap USB inline gadgets to measure voltage and current. I noticed that as the power bank approached capacity the panel voltage rose to about 6v as the current fell to zero. Will look at a dc2dc as you suggest.

I'm supposed to respect my elders, but it's getting harder and harder for me to find one now.

neb

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#3107375 23-Jul-2023 20:54

In that case it could be just the power bank pulling the voltage down, so it should be OK. I'd also check the cable though, a sufficiently rubbish cable can lead to significant losses.

ezbee

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#3107558 24-Jul-2023 13:19

There is a Buck Boost converter at Surplustronics that might be worth a look.

DC to DC Step Up Step Down Converter - Buck Boost
https://surplustronics.co.nz/products/7518-dc-to-dc-step-up-step-down-converter-buck-boost-

NOTE...

Oh I made a mistake below, the minimum input voltage for this device is 5V , so may not work too much below 5V if at all.
With input and output so close it may be a bit of a crapshoot on how well it will operate, so may not work so well.

NOTE 2...
Well further down in spec on the product page above it says Input Range：3.8V ~ 32V, so as with some things from certain countries its an adventure of 'suck it and see' . I see elsewhere what looks like same board is listed down to lower input.
Sigh.... So may be perfectly fine.

""
This will do both step up and step down, its adjustable to very high voltage so be super careful that you have adjusted it properly for 5V output.
̶S̶o̶ ̶t̶h̶i̶s̶ ̶c̶a̶n̶ ̶s̶t̶e̶p̶ ̶u̶p̶ ̶v̶o̶l̶t̶a̶g̶e̶ ̶t̶o̶ ̶5̶V̶ ̶i̶f̶ ̶y̶o̶u̶r̶ ̶S̶o̶l̶a̶r̶ ̶p̶a̶n̶e̶l̶ ̶i̶s̶ ̶d̶e̶l̶i̶v̶e̶r̶i̶n̶g̶ ̶l̶e̶s̶s̶ ̶t̶h̶a̶n̶ ̶5̶V̶ and step down voltage to you set 5V if panel is putting out higher voltage.
Just watch the output voltage and be sure to adjust to 5V before connecting to your battery.
""

Test on a supercheap power bank first might be an idea.

I remember the old shop in upper Queen Street a 'dusty' cornucopia of all sorts of parts.
Somewhat of a history of electronics progress and companies that were once.

Andreas Spiess has some videos on smaller Li-Ion charger boards though more to charging one or two separate cells for small projects.

Solar Charger for Microcontrollers
https://www.youtube.com/watch?v=dBx-g1dkdDQ

The 5 Best Solar ChargerBoards for Arduino and ESP8266
https://www.youtube.com/watch?v=ttyKZnVzic4

neb

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#3107615 24-Jul-2023 15:45

You can also get a ton of DC/DC converters and similar circuit modules off Trademe, it's all Aliexpress stuff but stocked locally so you don't need to wait several weeks. There's also a bunch of hobby places for model aircraft and drones and whatnot that sell both via TM and their own web sites that have stuff like this, so it shouldn't be hard to find.

richms

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#3107618 24-Jul-2023 16:00

DC to DC off a solar panel doesnt work properly unless it is an MPPT type that will track as the available power changes.

Just feed it into the powerbank which will regulate it down internally to what the cell needs - either with a buck or with a linear regulator dropping it down depending on how cheap it is. 6v is still within what it will be fine with.

Richard rich.ms

peejayw

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#3107622 24-Jul-2023 16:10

OK, thanks all. I am going to run the panel and battery for a few weeks once the sun decides to shine and discharge it each night, see if it survives before I take it down to the beach to install.

I'm supposed to respect my elders, but it's getting harder and harder for me to find one now.

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ezbee

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#3108836 27-Jul-2023 18:19

You seem to have hit a lucky spot with the
Anker Powercore 10000 , as its QC Charge capable, it keeps on ticking with a 'little' > 5V level.

This chap in Ukraine designing his own MPPT has found differences below on different power banks he tried if voltage was allowed to be > 5V.

Next-gen DIY Solar MPPT controller - cheap, simple, efficient. Based on PIC12F675 MCU.
Evgeniy Evstratov
https://www.youtube.com/watch?v=ihknAuBgBg0

Note in Github c.main
""
- powerbank 1 (QC supported; device used in most of testing during almost all of development):
- tested powerbank can be tricked to trigger QC mode and rise voltage - when it's connected it "requests" higher voltage while consuming no substantial load
and the actual voltage can be rising at the moment so powerbank considers that everything is according to plan and accepts it;
- if voltage manages to rise higher than powerbank's limit - it will shut down and won't charge (*or powerbank will die - happened with one simple model when 12v was applied during testing);
- plain buck converter (when added after output) is apparenty fully "opened" and acts as a minor resistance (inductor+mosfet) with it's input and output voltages being almost equal;
- powerbank 2 (no QC no PD): pay attention at powerbank's capabilities - if it doesn't support QC/PD then it will likely die from higher voltages (not just shut-off).
- powerbank 3 (PD supported): denies voltages higher than ~5.3v and simply doesn't charge, often charges poorly with around 5v provided (doesn't consume all current available);
""
His Github has oldschool hand-drawn schematic and pics of how he wired the protoboard, full source code and details.
The hand assembly with through hole parts on proto board reminds me of decades ago when it was common.

This comment in code is sad though.
""
This Solar controller is being developed in these dark times when Russia is destroying energetic system of my country and has already caused full-scale blackout.
""