Re: Discuss: Solar Charger & battery pack for the Raspberry

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cottonpickers
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Re: Discuss: Solar Charger & battery pack for the Raspberry

Postby cottonpickers » Sat Jun 22, 2013 7:38 pm

MC: It depends on sun in your area. It will be 'touch and go' to last 24x7. I think on sunny days you would last through the night but not on cloudy days. You definitely would not get 24x7 7 days a week every week. You can do the maths yourself by adding up the power draw and how much power the panel puts back in.

To run the Pi A with a wifi dongle and just using the inbuilt SD card (maybe get a 64Gb card??) 24 hours you need ~6000ma of juice. My panel will supply 1500ma maximum an hour. So you would need to guarantee 4-5 hours of good sun every day to generate that 6000ma.

You could add in a second panel to then halve the number of hours sun you need. Just depends what the sun is like with you and how important it is to run every day. My upcoming Timer would let you switch off for some time each day and make a difference.


Aikidokajeff
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Re: Discuss: Solar Charger & battery pack for the Raspberry

Postby Aikidokajeff » Sun Jun 23, 2013 1:29 pm

About the USB timers, are they going to only be connected for power or will they allow data too?
I had thought about how good they would be for turning on USB devices like cameras or WiFi dongles.

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cottonpickers
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Re: Discuss: Solar Charger & battery pack for the Raspberry

Postby cottonpickers » Sun Jun 23, 2013 7:48 pm

The USB timers will be power only. The good thing is that it means they will be useable on lots of other things that use USB power (like you say, cameras for example) They will have a male and female USB port on them.

Aikidokajeff
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Re: Discuss: Solar Charger & battery pack for the Raspberry

Postby Aikidokajeff » Sun Jun 23, 2013 7:52 pm

O well, I'm sure they'll still be great.
Would have been handy to connect up a USB web cam through one and have it come on and off when rimmed.
Or WiFi to do the same, just leave a script checking for WiFi and do stuff only when it is powered up.

Excited nonetheless.

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Re: Discuss: Solar Charger & battery pack for the Raspberry

Postby cottonpickers » Mon Jun 24, 2013 6:08 am

Aikidokajeff: Hmm. I think I'm understanding you better now - I don't think I could get it to switch the data lines as well as power but I think I could leave the data lines in tact (by request) so that the power is only removed - leaving data lines in place even when off. I'll take a look when all the parts are here, but that should be possible. I Think this would mean that you could use it to 'switch' on and off a peripheral such as wifi dongle. So long as the dongle is happy being plugged in without power but with data lines. (I'm guessing this is similar to leaving plugged in to a USB Hub that is not plugged in to the mains (if that makes sense!)

Aikidokajeff
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Re: Discuss: Solar Charger & battery pack for the Raspberry

Postby Aikidokajeff » Mon Jun 24, 2013 6:51 pm

Yep that's what I was thinking.

adgrpi
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Re: Discuss: Solar Charger & battery pack for the Raspberry

Postby adgrpi » Fri Jun 28, 2013 1:10 pm

to Cottonpickers, apologies for delay in replying. Thanks for the recommendation. I have just placed an order. Regards, Andy

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Re: Discuss: Solar Charger & battery pack for the Raspberry

Postby adgrpi » Sat Jun 29, 2013 10:57 am

To CottonPickers,
What would you consider to be the longest cable from the solar panel to the battery pack? Would you be able to supply with my order (happy to send more payment)? Ideally I would want 5 metres but unsure how feasible this is. I need to place the battery at the further end alongside the Raspberry Pi.
Regards,
Andy

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cottonpickers
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Re: Discuss: Solar Charger & battery pack for the Raspberry

Postby cottonpickers » Sat Jun 29, 2013 11:10 am

Andy: Hmm. Its all about voltage drop....When the voltage is low and the wire is thin the voltage drops quickly. Its why we have high voltage transmission lines to move electricity over long distances (the drop is much lower when the voltage is much higher) If you 'fatten' the cable it also helps, or if you can keep the current low.

I use 24awg cable. Over 5 meters and about 1500ma the voltage drop is quite high (it will take it to about 4v) I do have thicker 18awg cable here that would help but still that distance will drop voltage to about 4.6v which is still 'touch and go' If you could put the battery pack half way (so 2.5m away) and maybe I could make one up without a diode it would help and you could stay at 5v. Here's a good voltage drop calculator that you can use to make some judgements: http://www.calculator.net/voltage-drop- ... &x=47&y=16

One other option is that I have a 1amp 6v panel, that using 24awg cable would drop you to 5v pretty much exactly. Obviously its not a 1.5amp panel though, but may be worth considering. Its 26cm x 18cm.

This also indicates that you might want the 1.5amp panel loose? and not attached to the project box? - let me know and I can tailor it for you.

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Re: Discuss: Solar Charger & battery pack for the Raspberry

Postby cottonpickers » Sun Jun 30, 2013 7:11 pm

Andy, Here are the bits all ready to wrap up and put in the post. The wire is 24Awg and is 3m long. I've included a spare USB port so if you do need to cut it down and are handy with a soldering iron you can wire it back up. As you are separating the panel from the electric box I've left the panel separate rather than my normal method of putting it directly on top. I've also included the small fan that I'm including in future with all 1.5amp panel/box combos - I don't think you'll likely use it but included anyway. For others, the idea is that you wire the fan direct to the panel on the 'before' diode side so that it will come on whenever the sun shines - and when the sun goes in the fan stops. it uses 150ma (10%) so I won't install by default in case people want to squeeze the most power from their panel.

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