FS: Solar Charger & Battery Pack for the Raspberry Pi-Ver 9

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cottonpickers
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FS: Solar Charger & Battery Pack for the Raspberry Pi-Ver 9

Postby cottonpickers » Sun Feb 17, 2013 8:13 am

Image

This has following features:

The Pi will draw power from the sun or from the cells seamlessly switching between the two. As the 'B' Pi draws about 440ma with a wifi adapter installed the panel is large enough to both power the PI on a sunny day and also recharge the battery at the same time. When the sun goes in, the batteries take over. The lower powered 'A' Model can theoretically be powered all summer without mains.

920ma PanelRequires 4 AA NiMH and/or 4 D NiMH cells
2 USB ports
* One is Apple compatible
* One is Standard/non-Apple
Linkable - You can double the battery storage and double the solar harvesting by adding a second unit.
Switch to turn on/off the PI whilst still allowing the batteries to charge in the sun when off
LED to indicate when the sun is out ;-) and give you that warm feeling that panel is doing its job
Can be plugged in to a USB socket when the sun is not around
Both AA and D Cell battery holders.

You can put in either NiMH AA or D Cells, Or both.

When loaded with both AA and D cells , you should get over 10,000 mah of storage - easily enough to run the PI overnight, or if you have the lower power 'A' Model it *should* run for 2 days :twisted: without sun.

Of course, you can also use it to charge your iPad, iPhone, Android or whatever....

It will run on just 4 AA cells, but the panel is large enough to overcharge 4 AAs if the sun is strong and the pi is off. So either leave it switched on, or use some D cells in addition to the AA's or instead of them. There are some AA->D converters if you don't have D cells.

If you can't get hold of decent D cell Nimh cells, I may be able to help. I have some genuine 8000ma Maplin cells I could supply to UK folks.

This will become a standard offering Model (alongside the Ver 7) priced at £35 for UK folks
Panel size is 26x18cm .

As a thank you to people who have registered AND made a posting on this thread before today [16 Feb 2013] I'd be delighted to offer this model at the same price as the V7 (eg £25 for UK folks) . Going forward, I hope to offer further thanks for people who contribute here.

How do I order? Simply click the appropriate Paypal link below. You don't need to have signed up to Paypal in order to pay:





Nickb23
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Re: FS: Solar Charger & Battery Pack for the Raspberry Pi-Ve

Postby Nickb23 » Tue Feb 26, 2013 9:07 pm

Hey Cotton,
Just received mine. Many Thanks!!!! Just to confirm, the iphone port also charges ipads!!!

Anyway, I have a couple of questions. I know you said it can be charged via usb if there is no sun. I presume it is the dangling usb cable that you plug in? Is there anyway to know if it is charging? Does it cut off once charged?

Secondly, with the daisy chaining them - Is it possible to make a secondary usb only Solar Panel, so that you can effectivly double the panel space, without doubling the battery packs?

Sofar got 4 2400ma AA's plugged in, and gonna get some hi capacity D Cells. Any ones you recommend??

Thanks again Cotton Pickers!! At The moment my Pi is in the fixers, so I am getting lots on enjoyment charging my iPad :lol:

Nick

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

Postby cottonpickers » Fri Mar 01, 2013 7:51 pm

nick: Thanks for the feedback!
yes it's the dangling USB lead to use if there is no sun. it won't fully charge the NiMH cells I'm afraid, only give them a light charge if they are flat.
I can supply a second panel without the boxes attached, just the panel and USB ports but I recommend batteries also in the second unit to increase run time. if you just want the panel I would suggest a 5.5v panel instead which is a little higher current and won't over charge the cells. price is the same as a ver7
Ideally you want high quality low discharge, high man cells at a good price. the problem is you can't get all three together :(


These are the highest capacity but not low discharge

These are the highest capacity LSD cells

These are a reasonable price performance compromise

Alternatively use AAs in a converter like this:

or I can sell some new unopened maplin 2xD cell low discharge cells 8000mah for £12 with any of my solar panels.

Nickb23
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Re: FS: Solar Charger & Battery Pack for the Raspberry Pi-Ve

Postby Nickb23 » Sat Mar 02, 2013 12:19 am

Damn. I wish I read your reply earlier. Just been to maplin where I have just bought 4 x 2800ma d cells for £9. These would be ok, wont they?? They were on at half price :-)
I need a really quick idiots guide to power and batteries. I have got 4 2400 AA's and now 4 2800 D cells. Do I just multiply the ma number the numbers up to tell me how much capacity I have?

Thanks in advance.
Nick

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

Postby cottonpickers » Sat Mar 02, 2013 6:39 pm

Nick: basically multiply voltage by capacity to give you total energy in watt hours. So 1.2 x 2.4 =2.8 watt hours in each cell. If you have 4 of these you have 11.2 watt hours there for your £9. This isn't bad for the price. By comparison the 11000mah cells hold 1.2 x 11=13.2 watt hours each. If you had 4 of them it would total 52.8 watt hours but cost an eye watering £48
The pi model b uses about 400mah at 5v so this is about 2 watts per hour (.4 x 5) The model a uses apparently one third of the power so I guess 0.7 watts an hour. Your cells on their own should last about 6.5 hours on their own. If you added in some aa's it would last longer.

Hope you follow ok as it's not easy.

Nickb23
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Re: FS: Solar Charger & Battery Pack for the Raspberry Pi-Ve

Postby Nickb23 » Sun Mar 03, 2013 8:35 pm

Thanks cotton. That makes lots of sense :-). So i have 4 aa's @ 2450ma and 4 d's at 2800ma. So this means that I have 25.2 watt hours. This means that I should be able to run the pi for 12.6 hours. Now I am also going to add a wifi usb dongle aswell as a 64gb usb key to share data from. Once I have all my bits, is there a way to work out / test how much power is being drawn?

To work out how long ut takes to charge, is it a case of adding up all the ma's of all the batteries (12600ma) then dividing by the solar power (920ma)? With everything off, does this mean it should take 13 hours?

Thanks for all your help. I have learnt more about electriity and power in the last couple of days than I ever did at school ;-)

I think when I can I will upgrade to bigger cells. Can I mix capacity sizes of the d's? Just so I can buy some this month and buy more next?

Nick

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

Postby cottonpickers » Sun Mar 03, 2013 9:26 pm

Nickb23: To test how much your pi is drawing you need to buy a 'digital multimeter' and put it in betwetn the pi and the panel/batteries. I've done this and found the pi uses 420ma (see my graph on the thread somewhere) or about 440ma with a wifi dongle. Its hard for you to do this now without cutting the pi microusb lead and splicing it in there. You could try between the battery and the spring. I can guide you if you fancy giving this a go. DMM's are about £6 on ebay or £10 at maplin.

The panel charges at a higher voltage (lets call it 5v for simplicity, so it charges 4 cells (or 8 cells) at once at 900ma so you can actually bundle the mah together. If the panel charged at 1.2v you woul be right, but as it charges at a higher rate it will be quicker. So you have 2450 + 2800- 5250ma @ 4.8v , so the panel at the same 5v will take 5250/900 = about 6 hours if my math is OK!

If you do swap any of the batteries you need to do them in 4's to get the benefit, otherwise you will get one weak battery and the voltage will sag as soon as the first one is empty. If this happens the pi will shut off, even though the other 3 batteries may be half full etc. If you are upgrading your cells you could look for a dual AA to D converter an buy another set of 4 AAs. Just a thought. You then place two AAs inside the D shell . Its just a cheap way to use your existing cells and add to them.

Nickb23
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Re: FS: Solar Charger & Battery Pack for the Raspberry Pi-Ve

Postby Nickb23 » Mon Mar 04, 2013 6:04 pm

thanks mate. I do own a digital multimeter for a problem I was having with my car :-) Still trying to work out how to use it.
If I buy one of those double AA to D convertors, if I put in 2 2400ma AA's, does this make each D cell 2400ma or 4800ma?

I am sorry how stupid I must seem, but my god electronics is like a different language to me!!!

Nick

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

Postby imigueldiaz » Wed Mar 06, 2013 9:34 am

Hi!

I would like to know if this model could support both a raspberry pi B with wifi nano adapter and usb 3G drive and an external 1TB hard disk, It would be located on Madrid (Spain) and with lots of sun hours. It could be possible to adapt to these requeriments?

I'm programmer, but I've no skills on electronics...

Excuse my english, Spanish is my native language ;)

Best
Ignacio

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

Postby cottonpickers » Wed Mar 06, 2013 8:51 pm

NicK: Great, its fairly easy then! Set your DMM to 10A setting (you could use the ma setting but I don't know how high it will go, so best use the high current setting) then put the black lead in COM and the red lead in 10A. Now switch on the dmm and set it to "A" or "Amp" and make sure its on DC not AC. Now you are ready to test! - just half lift out one of the batteries and put the DMM in between the battery and the spring. Something like this SPRING<---------DMM------->Battery-Battery-Battery-Battery-SPRING so all the electricity goes through your DMM and can record how much its using. You will get a reading of about 0.4amps (ie 400ma)

Ignacio: Rapberry Pi B uses 400ma wifi Nano uses 40ma usb 3g drive is maybe 100ma?? External 3.5inch 1TB drive is about 2,000ma -3,000ma

This is too hard to do :-( a laptop hard disk is better. 2.5inch 1Tb is about 500ma. Still quite high

I think you need to look at SD or USB thumb drives.


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