How much powerful solar battery do I need to power the Raspberry Pi 4B at load and charge batteries to enough energy amount to work at night?

Question

I need Raspberry Pi that will work autonomously long time. I think about solar panel what will power Pi at day and charge batteries for the night work till the next sunrise.

So, how much powerful panel do I need (50W, 100W, more?) and what total capacity of 18650 cells should I collect to keep Raspberry Pi working forewer?

How that params will changes if we replace Pi 4B by Pi Zero W?

The Pi's electrical consumption figures may be found on-line. Add to that the consumption of any peripherals you plan to use. The question then becomes how do I provide this amount of power which is not a Pi specific question. — joan, Jul 28 '22 at 15:14
Please prepare a power budget similar to the one outlined here. That may help you think through this. — Seamus, Jul 30 '22 at 05:39

score 3 · Accepted Answer · edited Aug 05 '22 at 08:13

A Pi 4B will consume about 6W with 4 cores busy. With some safety margin, power consumption of the converter and without peripherals, you would use 10W or 2A for your calculation.

For the rest, you need to do some calculation. But you will need much more information than we can find in your question.

In the ideal situation, you will get 12 hours of sun and 12 hours of night. If you always get sun the full time, you would need a battery of 24AH and a panel of 20W
But if you're a bit more north or south, in the winter you will not get 12 hours of sun. Beyond the Arctic and Antarctic Circles, you will even get days without sun. So, you will need to take that into account too. This will increase the size of your battery (and the need for power from the solar panel)
Your days may be shorter and they may be cloudy, so you will need some extra capacity from your solar panel to cope with that too. You may get some statistics from people with solar panels on their roof
If you want to be surer that the Pi stays up, add a factor 2 at the end of your calculations
Even with the factor two, make sure you have a graceful shut-down when the battery is low, and some circuitry that reboots the Pi when power is sufficient again.

There may be more things required for calculation. For example, batteries perform bad when it's cold.

You will need too many 18650 cells for that to be a viable storage solution for the power. Do yourself a favour and look at lead batteries that are also used in UPS-s.

The zero obviously consumes less power, so you will be able to use smaller batteries and solar panels.

Good luck.

----added----

If you go for a solar powered solution and your solution runs on a zero, that is the way to go.

You can disable cores in the Pi 4 by adding maxcpus=1 in /boot/cmdline.txt. How much that will save is debatable; I've seen figures of +/- 40mA per core, but you should measure yourself.

So, correct me if I wrong. If RPi uses only 10W and solar battery provides 50W in the current conditions, so, I can use 10W for RPi consumption and 40W for batteries charging (if not count loses). Right? — Robotex, Aug 01 '22 at 14:04
I guess LiFePO4 batteries will be ideal in this case.
Is it possible to limit the power consuption of RPi? For i.e. allow to work only one core. — Robotex, Aug 01 '22 at 14:06
Your power calculations are right. But beware of the influence of the seasons and the clouds. — Ljm Dullaart, Aug 01 '22 at 15:12

How much powerful solar battery do I need to power the Raspberry Pi 4B at load and charge batteries to enough energy amount to work at night?

1 Answers1