Power Raspberry PI using Solar Panel

Finger-in-the-air measurement came out to 6 hours. There's about 30Wh of energy in three cells total (that's more realistic than assuming that they support precisely what they are labeled as), and if you're running a Pi and SSD, I guessed at 5W, but there will be some losses too in conversion. So that's ballpark 6 hours, maybe +- 1 hour for the conversion losses and actual battery capability being slightly different than my guess). I think if you don't wish to change hardware and if OS and software can not be tweaked further then the battery is possibly the current bottleneck (but I've no idea if more solar capability is needed if the battery size is increased).  

I have a few suggestions:

1) you may consider changing to a lighter Raspberry Pi model - like a Pi Zero or Pi Zero W.  Capturing photos doesn't take a lot of computing power.

2) you may consider losing the SSD.  If you are simply taking photos at night, you can probably capture on the Micro-SD and offload in the morning w/o problems if you have a large enough card.

3) depending on where you've placed your equipment, low temperatures can severely affect your battery discharge.

4) finally, you should try to measure the average current load of your running PI to estimate how to size your battery plant.

Good luck!

What's the time interval like between image captures ? Can you shut the power-hungry R-Pi 4 down between images and then use an ultra low power microcontroller to wake it up before the next one is due ?

Looks like AllSky can run on a lower-powered R-Pi:

"A Raspberry Pi (Zero 2, 2, 3, 4) running Pi OS."

Slow down the clock ? Add another battery pack in parallel ? For sure if the nights get longer , it will need longer life.

beacon_dave said:

Can you shut the power-hungry R-Pi 4 down between images

It looks like there’s no sleep-wake mode on the RPi  (unless that’s a recent addition?), so like you said, it would have to be a shutdown-halt, and then the micro controller triggers a reset (restart).

You’d have to reduce the start up as much as possible, and I wonder if the starting power draw would offset the savings?

It looks like the default for that AllSky software may be 10-second exposures, every 10 seconds, so it's possible the Pi cannot be shut down unless there are boring intervals (e.g. if one is only interested between certain times of the night maybe). A lower power Pi is definitely a good idea! I think Pi 3B used a lot less power than Pi 4 (from memory), so that would squeeze out another hour or two.

Hi !

I know that in the winter, with longer nights, I'll need more power. How would that work ? A parallel battery pack ? I'm all for that.

I could use a lower RPI, but this is the one the recommend. They even go for the 8GB memory RPi 4. Probably a less power hungry one, like a RPi 3 b+. I have those . I will try .

The pictures are 1 minute apart during nighttime.

Thank you.

I went for the SSD because of space. A SDCard will surely draw less power. I will try with a SD Card.  I will consider a 3B+ . They don't recommend Pi Zero (1 or 2) .

I'm from Portugal. Now, it's summer. In my town - interior of Portugal,in the middle of the country, almost near Spain, I'm getting 35+ degrees celcius during the day and 20+ at night..

I have one of those usb devices that measure power - will check that.

Voltaic do some larger solar power banks which might be worth a look ?

https://voltaicsystems.com/battery-packs  

Their larger laptop ones are designed for use with 18v panels and are rated at 88.8Wh and 246.6Wh capacity.

They have an 'always on' output power feature as well.