mark2fly1034
Posts: 1
Joined: Sat Mar 05, 2016 3:49 pm

Powering Pi 2

Sat Mar 05, 2016 3:54 pm

Hello I am trying to set up a pi that will not be able to run off a wall outlet as one would be to far away, I bought Solar Charger, Solar External Battery Pack, iBeek® Portable 12000mAh, and it appears it was not able to run in the overnight hours. I was hoping with the solar charger that it would be able to charge up all day and then use the battery during the night. The room where it is located is well lit during most of the night there is around a 5 hour period where no one is in the office so the lights do turn off. Any help on what to do without having to use a 45 foot extension cable?

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GTR2Fan
Posts: 1601
Joined: Sun Feb 23, 2014 9:20 pm
Location: South East UK

Re: Powering Pi 2

Sat Mar 05, 2016 4:13 pm

Roughly whereabouts in the world are you? If you're somewhere in the UK or northern Europe, expect to need a high quality photovoltaic panel approximately the size of a house door to keep up with it at this time of year.
Pi2B Mini-PC/Media Centre: ARM=1GHz (+3), Core=500MHz, v3d=500MHz, h264=333MHz, RAM=DDR2-1200 (+6/+4/+4+schmoo). Sandisk Ultra HC-I 32GB microSD card on '50=100' OCed slot (42MB/s read) running Raspbian/KODI16, Seagate 3.5" 1.5TB HDD mass storage.

klricks
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Joined: Sat Jan 12, 2013 3:01 am
Location: Grants Pass, OR, USA
Contact: Website

Re: Powering Pi 2

Sat Mar 05, 2016 5:10 pm

mark2fly1034 wrote: ....I was hoping with the solar charger that it would be able to charge up all day and then use the battery during the night. The room where it is located is well lit during most of the night there is around a 5 hour period where no one is in the office so the lights do turn off. ....
I don't believe you can expect to get sufficient charging on indoor lighting alone if that is what you are doing. The panel(s) need direct outdoor sunlight. Even that may not be enough depending on the time of year and size of panel(s) etc.
Last edited by klricks on Sat Mar 05, 2016 5:16 pm, edited 1 time in total.
Unless specified otherwise my response is based on the latest and fully updated Raspbian Buster w/ Desktop OS.

JimmyN
Posts: 1109
Joined: Wed Mar 18, 2015 7:05 pm
Location: Virginia, USA

Re: Powering Pi 2

Sat Mar 05, 2016 5:15 pm

During the day when it's charging the battery the solar panel will also need to power the Pi. So the solar panel has to have enough output to do both at the same time. How many watts is the solar panel?

HankB
Posts: 127
Joined: Fri Jan 01, 2016 2:45 pm

Re: Powering Pi 2

Sat Mar 05, 2016 8:24 pm

Hi mark2fly1034
My Pi 2 is sitting in front of me with an HDMI cable, Ethernet cable and Logitech unifying receiver plugged into it. I have a USB meter between it and the wall wort that shows it using about 250 mA. (These meters are under $10US on Amazon.) With a fully charged 1200 mAH battery I would expect it to run 1200/250 => 4.8 hours. You'll need something bigger to get you through the night. Things that could affect this estimate:
* Difference between rated battery capacity and what you actually get (efficiency)
* Difference in load for your Pi 2 - depending on what's plugged into it and what it's doing.
* Benefit from indoor lighting - depends entirely on your solar panel and how bright the lighting is. Might reduce battery draw a little.

If this system is unattended overnight you can see how long it runs with your present setup and gauge what you have to do to get all night operation. This little shell script will update the timestamp on the indicated file every 5 minutes (300 seconds) until the system dies. It's not really good to shutdown that way so backup your files first in case it results in corruption. (Most of the time any corruption is automatically fixed on the next boot.)

Code: Select all

while(:)
do
touch timestamp_file
sleep 300
done
Do not leave the 'sleep 300' part or the script will generate a lot of disk I/O activity and use more CPU. I tried it for a bit and it drove CPU usage to 27% and power usage to ~400 mA.

HTH,
hank

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