Hi, I’m a first year engineering student and I’m in the process of attempting to make my first solar powered raspberry pi pico w. I’ve done my own look into what is necessary to achieve this but I just need to understand it all before I attempt it on my own..
My current list of supplies to make it solar powered include: a 4.5-6V solar panel, a lipo battery and a sunflower solar power manager.
My queries about this project include:
Does a USB connect between the solar power manager and the raspberry pi power the circuit or is it done through a different way?
Does the power manager need to be coded in any way, or is it just considered a power source like my computer would be for it.
The solar power manager suggests a 3.7V 900mAh lipo battery, will it be fine with a 1000mAh battery?
And lastly, what is a good recommendation for a solar panel, I need something small so it makes the project convenient :)))
Any other words of wisdom that might make my project even more advanced and organised will be very helpful as well!!
Unfortunately “small” and enough current supply don’t usually go together. Depends a bit on panel efficiency but unfortunately the sun only has a finite amount of energy per square metre and you can’t improve on that.
But your current requirement would be fairly small as I understand you are only powering a Pico with no added peripherals.
Cheers Bob
Sounds like a fun project! Hopefully we can answer all your questions without much issue.
The general topology of your project is correct, so I’ll just address your talking points one-by-one. To assist, here’s the labelled product image from the product page.
The Raspberry Pi will be powered through the “USB 5V OUT” port. This is a regulated output that can supply up to 1A at 5.1V. Just plug your Pico into this port with the standard Micro-USB cable and you should be fine. External boards and circuits could be powered using the Pico’s VBUS rail, or by plugging them into any of the red pin headers on the power board (not sure of the exact internal circuit but these are not directly connected to the USB-5V on the PCB).
The Sunflower Solar Power Manager does not require any programming. It is fairly “plug-and-play”. I would be careful classifying it as a “normal power source” as you delve deeper into the project, but from the perspective of the Pico, it can be considered one.
I believe the 900mAh suggestion arises from the maximum output current of the charge circuit. The capacity of a battery does affect some of the characteristics of the circuit. But these typically only become an issue at much larger sizes. Replacing the 900mAh with a 10000mAh may be cause for concern, but a 1000mAh won’t cause issues at all.
As Bob mentioned, it can be hard to get adequate power from a small panel. Additionally, the charge circuit efficiency is approximately 73%. A board like this 0.5W Solar Panel from Seeed Studio could be enough. It provides a nominal output of 5V@100mA (0.5W), which means (factoring in the efficiency) the battery charge current will be 98mA.
Not particularly high, but might be sufficient depending on your current requirements (What kind of stuff do you want the Pico to do?), though keep in mind that this is the ideal current supply, and it could be lower.
Another option is this 3W version also from Seeed. Which should charge at about 600mA (same calc as above). Though it has about 6x the surface area (who could have seen that coming??).
A couple of extra things I noticed while writing this post:
The power manager can only accept a voltage up to 6V, but these panels can have an output up to around 10V (typical output is still 5V, but could be up to 10V). You can likely create a simple circuit to prevent this from causing any damage, perhaps others will have some useful input on this.
The power manager does not provide overdischarge protection (LiPos can discharge enough to damage themselves if not prevented). Generally you can get LiPo cells with this built-in, so I’d suggest picking one of these up.
I know of others with the low-power objective setting up an auto-sleep/wake-up system for their projects. The idea being that the device will either turn itself off completely, or enter a sleep mode, for a portion of time while not being used. It might be worth looking into if you’re interested.
Hope this helps! Let us know if you have any other questions.
I’ve successfully solar-powered my Raspberry Pi Pico W by using a 6V solar panel with a charge controller to regulate the power. The charge controller connects to a 3.7V Li-ion battery, which powers the Pico when there’s no sunlight. I also added a diode to prevent backflow of current from the battery to the panel.
I used a TP4056 charging module for the battery and a LM2596 step-down converter to make sure the voltage stays stable.
The Pico W doesn’t consume a lot of power, so a small 2W solar panel works fine for my setup.
Make sure to check the battery voltage regularly, as deep discharges can shorten its lifespan.
I have one of these DFRobot Solar Power Manager 5V boards with an old 6600mAh LiPo and a 5V solar panel for my hobby greenhouse which uses an ESP32-S3 with several sensors.
Yes 5V power only is passed to your Pico via the USB-C out socket. No additional hardware or software is required … unless you want your Pico know when the battery runs down (say to allow it to power down gracefully).
I doubt there is any technical limit to the size of battery … just the usual financial reason But the bigger the battery (a) the longer it will keep your pico running when the weather is not sunny, but (b) the longer it will take to reach full charge when there is sun. Yeah, I’m paranoid about having a string of wet weather.
The sunflower seems to have over discharge protection set at 2.8V - which I and many others consider too low. You may wish to implement your own protection, possibly by putting your Pico to sleep or maybe powering if off … which means you do want to know the current battery voltage.
This happened one day while I was bench testing and didn’t notice how quickly the battery ran down.
I bought my solar panel from aliexpress (which I do NOT recommend) and find that all during daylight hours the voltage is 4.3V with the current depending on cloud cover and angle of sun. Do remember that the calculation of charge current is theoretical, and that the sun probably won’t be shining directly onto your solar panel all the time.
I note however that peaks of voltage up to 6.3V were recorded … I hope they were an aberration of the reporting, and not going to blow up my power manager board.
The Sunflower Solar Power Manager is a hardware-only module — it doesn’t need any programming. It handles Solar energy harvesting, Battery charging, and Power path switching between solar, battery, and USB. So treat it like a smart power supply. Your Raspberry Pi Pico W doesn’t need to talk to it unless you’re monitoring battery levels through additional sensors.
I bought a 3 PIN 1000mAh battery, the power manager uses 2 PIN. Do I need to get a 2 PIN battery or am I able to work around this with a 3 PIN battery that I have.
Next, the solar panel is 2 PINS, and there are no pin inputs for the solar panel, can you deconstruct the ‘pin case’ around the end and use it in the 5V solar panel IN, in the respective places.
The third pin on the 3-Pin LiPo variants (the yellow one) is a thermistor (temperature-dependent resistor). It’s typically used to track the temperature of the pack, so it doesn’t explode. It isn’t strictly necessary for standard function of the LiPo.
I would probably just cut and strip the cables and plug the red and black wires into + and - “BAT IN” screw terminals on the PCB. Best practice would be to heat-shrink the empty thermistor cable so it doesn’t contact anything.
The same thing goes for the solar panel. I would cut and strip the wires and use the + and - “SOLAR IN” terminals.
Keep in mind, if these are Core products, cutting the wires will void our return policy as the device will have been modified (for the battery and solar panel). The alternative is buying a 2-pin LiPo and a solar panel that outputs to stripped wire out-of-the-box.
But the bigger the battery (a) the longer it will keep your pico running when the weather is not sunny, but (b) the longer it will take to reach full charge when there is sun. Yeah, I’m paranoid about having a string of wet weather.
