Pi Off-Grid-Project : powered by power bank and solar-panel: some calculations

[dhubs]

dear friends hello and good evening,

A new little winter project is just around the corner: I still have a few Rpi3 lying around here - and I've had a few projects in mind for a while - some of which are "off-grid" - because a Pi is particularly suitable for that. It requires comparatively little energy - can be operated with a battery or, if necessary, a small solar panel. But to ensure that the energy is always sufficient here, so that the operation is "stable", a lot of preliminary considerations are necessary - and that's why this thread:

My question is: Can I power my Rasphberry 24/7 with a solar panel and a 5000mAh power bank? Or to put it another way - how big does the panel have to be? So a small one Off-grid project in the planning phase:

At the beginning I think about the stable power supply: What if I want to recharge the power bank with a PV solar module: How big does this panel have to be!? The thing is, if I can't charge the battery, the RPi won't run for more than 5 or 6 hours. So for the remaining 18 hours of the day we rely on the panel, whose characteristics are rather low, to both power the RPi and have enough left to charge the battery for the next 6 hours...

Do you have any experience here - have you ever done something like this?

Approach: So I think at the beginning I have to determine how much power the Pi actually needs to run for a whole day,
So at the beginning I need a rough estimate of power consumption, charging requirements and solar output; So I can then determine (or estimate) how big the PV solar panel should be?

Do you have any experience with power supplies that include a PV panel in such a way that operation is guaranteed over the long term? At the moment I'm particularly interested in how big the PV panel should be.


I'm looking forward to hearing from you!

[michaelk]

How much current depends on CPU load and if you are using USB, wifi or even bluetooth. You can turn off unused peripherals. Worst case for a Pi 3 would be somewhere around 1.3 amps but you might want to measure the actual load with it up and running everything like it would in actual use. Basically the current load in amps x estimated run hours x 1000 would be the size of the battery in mAH. You might want to oversize it by some factor. Worst case a 5000 mAH battery would last around 4 hours.

How much daylight depends on where you are located in latitude... The solar panels needs to provide enough current to power the Pi plus charge the batteries. Basically how laptops do it.