FS: Solar Charger & Battery Pack for the Raspberry Pi- Ver 7

ersiko
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Re: FS: Solar Charger & Battery Pack for the Raspberry Pi- V

Postby ersiko » Fri Jul 12, 2013 7:10 am

Hi!

Nice stuff you got here! You rock :)

I was thinking about building a solar-powered raspberry, with wi-fi and the new pi camera. The first idea was to time-lapse my garden growing, but once I get it working, it can be a security camera and whatnot. Nothing really fancy, just to have some fun with my pi.

I've got the camera and the wifi parts covered, but now I'm looking for the solar and outdoors (waterproof) parts. I want it to run 24x7, so the batteries must last overnight. And foreseeing cloudy winter days, I would like some kind of charge indicator as well, so I can get a page alerting if charge goes down a certain level. And I'd like to put out outdoors, so it needs to be sealed.

As far as I can see, I could use one of your large sets, and seal the back inside some kind of tupperware... or did you any advance in waterproofing it?

Plus, is there in your set any way to measure the charge?

Thank you very much for your work and inspiration... keep up the great work!


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cottonpickers
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Re: FS: Solar Charger & Battery Pack for the Raspberry Pi- V

Postby cottonpickers » Fri Jul 12, 2013 8:18 am

ersiko:Thanks for the feedback!! For 24x7 running you really need to keep power requirements as low as possible and solar panel size as large as possible. Really this means looking at my 1.5amp Solar panel. The nice thing is that I do have a plastic box for it (the panels sits on top and the electrics in the box) As its exactly A4 sized panel you should be able to get alternate boxes if you prefer. To keep power usage low you should really look at the Raspberry Pi A version as it uses half the power. Finally you need to look at a large battery store to take you through the night. (Alternatively you could use my "soon to be available" USB Timer, which can switch the Pi on and off at set times each day/week) The 1.5amp panel does not come with batteries or a battery holder. Rather you would purchase a readily available 'External USB Power Pack' that can be charged by USB and can also charge USB devices. Many of these use 18650 sized Li-ion batteries that laptops also use, and come in a variety of sizes. I can sell an 'empty' 18650 External USB power pack for $15 and leave you to puchase the Li-ion batteries elsewhere (as I can't ship Li-ions) Hope this gives you some ideas.

ersiko
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Re: FS: Solar Charger & Battery Pack for the Raspberry Pi- V

Postby ersiko » Fri Jul 12, 2013 11:37 am

Interesting! That's pretty much what I was thinking... but what about monitoring the battery charge? Is there any way to measure it from the raspberry? This guy (http://pi.qcontinuum.com/project.html) used an arduino uno module, but maybe there are batteries with something similar integrated?

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cottonpickers
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Re: FS: Solar Charger & Battery Pack for the Raspberry Pi- V

Postby cottonpickers » Fri Jul 12, 2013 8:17 pm

Ersiko: If you use Li-ion then battery monitoring is really easy. Nimh voltage is not directly linked to battery capacity but with Li-ion it is. so 4.2v on Li-ion is 100% full. 4.1v is 87% 4v is 0.75% 3.9v is 55% and 3.8v is 30% with flat being 3.5v or below. You can use a mini volt meter (like the the pic in the top corner) or perhaps use the Pi to record voltage. (haven't tried this myself though..) Most of the external battery packs have a simple LED light system to indicate approx charge remaining...

ersiko
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Re: FS: Solar Charger & Battery Pack for the Raspberry Pi- V

Postby ersiko » Sat Aug 24, 2013 5:53 am

Hi again!

After the vacation time I'm retaking my project. I'm following your advice, and reading around the internet. According to this post http://www.raspberrypi.org/phpBB3/viewtopic.php?f=63&t=6050&p=291334&hilit=watts+power#p291334, a model B raspberry takes 600mA, so for 20 hours, I need (20x600=) a 12000mAh battery. And in this other post http://minipute.com/2013/07/08/qa-can-you-run-raspberry-pi-outdoor-continuously-on-battery-power/2049 they say a model A raspberry with a camera takes approx as much energy as a model B.

Off to look for batteries, then. This http://www.adafruit.com/products/353 seems to be an affordable battery, I could buy two 6600mAh batteries to get a >12000mAh. But I also read the raspberry needs 5V, and in the description I can read "3.7V". What are those 3.7 volts about? Is that the output? I can't use them with the raspberry, then, right?

After that I need a solar panel, but should be there a controller, too? Something beetween the solar panel and the batteries? Or they can be connected directly? How do you do that?

Thanks! And I've seen what a success is your solar charger v9, congratulations :)

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cottonpickers
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Re: FS: Solar Charger & Battery Pack for the Raspberry Pi- V

Postby cottonpickers » Sat Aug 24, 2013 7:12 am

ersiko: My readings show the pi drawing about a third less than the figures you have there , but either is OK for approximating runtimes.

That battery pack is made up of 3x 18650 Li-ion Cells (each one is a standard 2200ma cell) My Li-ion chargers would all charge that pack just fine and would cut out correctly when full, and can even include a mini voltmeter to show capacity like in the pic on this site however I think there may be better options.

You are right that these are 'nominal' 3.6v cells meaning that although their voltage varies from empty 3.5v up to full 4.2v we call them 3.6v (similar to 'nominal 1.5v AA batteries that also have a range of voltages over their life. You need to boost the voltage up to 5v to be useable. This also uses some energy to convert - as much as 20% but can be less if you have good circuit. In total these store 3.6v X 6600ma = 23.76watt hours. In comparison, my V7 pi stores 1.2v X 8800ma = 10.560 watt hours. Take off 10% or so for the conversion.

You could add these two together into a single larger pack.

I think a better solution is to source a 4 X 18650 Li-ion 'USB' Pack as this deals with the charging and also deals with getting the voltage up to 5v. You can also choose some better longer running cells (or if you prefer some cheaper ones)

For example the absolute best cells out there are GENUINE Panasonic 3400mah 18650 cells like these:

As they are rated and really do hit 3400ma you could get a pack with 3.6v X 3400 X 4 =48.960watt hours. So This would give you double the energy of the original idea in one single pack. The cost of the outside pack to do the conversion and protect cells from over charge and discharge etc is very low.

EG put them in a USB converter/Case etc like this


You would then have all the issues of converting voltage dealt with. The cells are then also replaceable etc. Are you US based? You should be able to get similar cells and packs, otherwise I can send the empty 18650 box for $15 or for UK folks purchasing with a panel 5GBP and you just need to source the 18650 batteries.

If you are looking at this sort of route, I recommend going with my 1.5amp (1500ma) Solar panel - perhaps in the water resistant box - as it can then charge these high capacity battery banks quicker. (around 8-10 hours of sun to fully charge)

ersiko
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Re: FS: Solar Charger & Battery Pack for the Raspberry Pi- V

Postby ersiko » Sun Aug 25, 2013 11:08 pm

Oh, very interesting!... I already bought the batteries and the case, using your links :)

Now I have ordered:
- Raspberry model A
- Raspberry camera module
- Wi-fi usb adapter
- 4 x panasonic batteries
- 1 x usb converter case

Now the only thing I need is the solar panel and something waterproof to wrap everything up. Mmm... no, wait... I'd also like some way to read the battery charge from the raspberry, so I can send alarms when the charge goes under some threshold (and make a fancy graph showing the charge percentage!). So I guess I still need something to read the voltage from the batteries and convert it to something that can be read by the raspberry... I'll look into it.
Meanwhile I'm foreseeing two problems...
- One of them is the temperature of the pack. Will the raspberry suffer or die for excessive heat?
- In my idea, there are two different things that need to be oriented: The solar panel (to the sun, of course) and the camera (to the area I want to photograph/record). I still don't know how big the camera module is, but I'm guessing I should mount it in an articulated arm, easily adjustable (at least easier than the solar panel :P).

BTW, where I was trying to make the design I was kind of lost reading, because there was too much information about different subjects. You're helping me a LOT, thank you so much for that :) I may name a son after you ;)

ersiko
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Joined: Thu Jul 11, 2013 11:46 am

Re: FS: Solar Charger & Battery Pack for the Raspberry Pi- V

Postby ersiko » Mon Aug 26, 2013 9:38 am

And I'm from Barcelona, I forgot to mention. Plenty of sun around here :)

Aikidokajeff
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Re: FS: Solar Charger & Battery Pack for the Raspberry Pi- V

Postby Aikidokajeff » Mon Aug 26, 2013 9:49 am

The camera module isn't much bigger than a postage stamp.
See it mounted on the front of this case.
You can see the pi and camera together.



jowi
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Re: FS: Solar Charger & Battery Pack for the Raspberry Pi- V

Postby jowi » Fri Sep 27, 2013 10:12 am

Hello CD,
Excellent idea. Order is already out, payment via paypal also. Best greetings from Bavaria, Schliersee 56km in the south of Munich - and 20km north of Tyrol / Austria ... Josef ;)


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