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rin67630
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Raspberry Pi Solar-Powered: Great OnLine Tool

Mon Oct 14, 2019 1:58 pm

For all people who want to power an 24/24/365 Off-Grid Raspberry Pi with solar energy.

You have got a great tool to dimension your system:

https://re.jrc.ec.europa.eu/pvg_tools/en/tools.html#SA

For example my system in Germany: 1 Raspberry Pi Zero W / Arduino with some low power instrumentation:

Consumption 200mA = 1W = 24Wh per day.

You will need a 100W labelled solar panel (real 80W) and a 240 Wh battery together with a good low-power solar regulator and an efficient DC-DC converter.

With a battery of only 200Wh you MAY get a day or two in Dec/Jan with discharged battery.
Last edited by rin67630 on Mon Oct 14, 2019 4:54 pm, edited 1 time in total.

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clicky
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Re: Raspberry Pi Solar-Powered: Great OnLine Tool

Mon Oct 14, 2019 3:14 pm

:+1: Nice find! Thanks for sharing...

I am curious to find out if it includes average raining days, too...

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rin67630
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Joined: Fri Mar 04, 2016 10:15 am

Re: Raspberry Pi Solar-Powered: Great OnLine Tool

Mon Oct 14, 2019 4:47 pm

clicky wrote:
Mon Oct 14, 2019 3:14 pm
I am curious to find out if it includes average raining days, too...
Yes. More than that. It bases on an extensive weather database. Several actually.

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Imperf3kt
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Location: Australia

Re: Raspberry Pi Solar-Powered: Great OnLine Tool

Tue Oct 15, 2019 12:23 am

Great post, will definitely bookmark this for future reference, if only to point out to people that their Pi will not run 24/7/365 on a "15W" solar panel because it's the same as the official power supply spec.
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W. H. Heydt
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Joined: Fri Mar 09, 2012 7:36 pm
Location: Vallejo, CA (US)

Re: Raspberry Pi Solar-Powered: Great OnLine Tool

Tue Oct 15, 2019 12:40 am

Imperf3kt wrote:
Tue Oct 15, 2019 12:23 am
Great post, will definitely bookmark this for future reference, if only to point out to people that their Pi will not run 24/7/365 on a "15W" solar panel because it's the same as the official power supply spec.
That and just how much battery capacity it takes to run continuously and allow for poor weather.

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rin67630
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Re: Raspberry Pi Solar-Powered: Great OnLine Tool

Tue Oct 15, 2019 5:33 am

Imperf3kt wrote:
Tue Oct 15, 2019 12:23 am
... their Pi will not run 24/7/365 on a "15W" solar panel because it's the same as the official power supply spec.
The example I gave was for a PiZeroW completely headless.
For a Pi 4 with e.g. a touch display or keyboard/mouse and an hour display on daytime, consider a 1000W panel and a good 120A/12V starter battery.

If you are located in Vallejo, in Australia or in Atlanta you get of course easier figures...

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davidcoton
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Location: Cambridge, UK

Re: Raspberry Pi Solar-Powered: Great OnLine Tool

Tue Oct 15, 2019 8:23 am

rin67630 wrote:
Tue Oct 15, 2019 5:33 am
For a Pi 4 with e.g. a touch display or keyboard/mouse and an hour display on daytime, consider a 1000W panel and a good 120A/12V starter battery.
You do not need (or want) a "starter" battery, because they are designed for a high current, which the Pi will not ever need.
What you want is a high capacity (measured in Ah or Wh) so that it can go on providing a very moderate current for a long time (days).
Leisure batteries (sold for caravans, for example) are a better buy for this purpose.
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rin67630
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Re: Raspberry Pi Solar-Powered: Great OnLine Tool

Tue Oct 15, 2019 10:03 am

davidcoton wrote:
Tue Oct 15, 2019 8:23 am
Leisure batteries (sold for caravans, for example) are a better buy for this purpose.
Are they not less common and hence more expensive at same capacity?

achrn
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Re: Raspberry Pi Solar-Powered: Great OnLine Tool

Tue Oct 15, 2019 11:01 am

rin67630 wrote:
Tue Oct 15, 2019 10:03 am
davidcoton wrote:
Tue Oct 15, 2019 8:23 am
Leisure batteries (sold for caravans, for example) are a better buy for this purpose.
Are they not less common and hence more expensive at same capacity?
Less common yes. More expensive for the stated nominal capacity, yes. The point is they are less expensive for the useful capacity, because you'll need a bigger nominal capacity starter battery to deliver the desired performance.

A starter battery has a nominal capacity but if you actually drain a significant proportion of that (say, more than 30%) more than a few times you'll wear out the battery. A leisure (or 'deep cycle') battery should deliver close to its stated capacity many times. If you buy a starter battery you'll need to buy one with a much bigger number on the side, and then it won't be cheaper.

There's no hard changeover between a starter battery and a leisure battery - it's a continuum of behaviour between things that will do very high currents for short periods and don't like being run down, to things that will do low currents for long periods but don't mind being drained relatively low.

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