Solarpanel and Batteries

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cottonpickers
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Re: Solarpanel and Batteries

Postby cottonpickers » Wed Oct 09, 2013 6:17 am

Andrie: Hi and Welcome!!
Personally I would not use a 12v 4.3inch screen (sorry to say that!) as it uses a different voltage from the Pi, so you have to manage two voltages from the same battery pack. Not impossible but just makes it all harder. Instead... I would suggest using your smartphone (Android, iPhone) if you have one, as the screen using VNC - Its dead easy to set up and means you bring the screen with you.
If you can make that change, then you can easily use my standard Ver7 or Ver 9 Model. Either should charge nicely in the day and run every night for about 4 hours or more. Both models have a USB output port suitable for charging your phone or powering a hub. Provided the hub doesn't draw too much power you should get a good use from even the ver 7 model.


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Re: Solarpanel and Batteries

Postby cottonpickers » Wed Oct 09, 2013 6:17 am

Andrie: Hi and Welcome!!
Personally I would not use a 12v 4.3inch screen (sorry to say that!) as it uses a different voltage from the Pi, so you have to manage two voltages from the same battery pack. Not impossible but just makes it all harder. Instead... I would suggest using your smartphone (Android, iPhone) if you have one, as the screen using VNC - Its dead easy to set up and means you bring the screen with you.
If you can make that change, then you can easily use my standard Ver7 or Ver 9 Model. Either should charge nicely in the day and run every night for about 4 hours or more. Both models have a USB output port suitable for charging your phone or powering a hub. Provided the hub doesn't draw too much power you should get a good use from even the ver 7 model.

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Re: Solarpanel and Batteries

Postby Andrie » Wed Oct 09, 2013 8:11 pm

Sorry I did not make myself clear the display runs of 5 Volt(s) I am just going to use a 12 Volt(s) power supply. :geek: :oops:
Last edited by Andrie on Thu Oct 17, 2013 9:13 am, edited 1 time in total.

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Re: Solarpanel and Batteries

Postby cottonpickers » Thu Oct 10, 2013 6:15 am

Andrie: Ah! that's good. It means you can use my low voltage (5v-6v) panels and maximise your Amps rather than use a 12v panel and waste energy converting it down to lower voltages. How long do you need to run it for? My V7 would be enough to test out the idea and run for an hour or so each day (I would think) or the Ver 9 would probably run for 5hours at a time but would need you to add some D cells (or get some plastic AA-> D converters)

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Re: Solarpanel and Batteries

Postby Andrie » Thu Oct 10, 2013 1:43 pm

Hi David (If I am correct), my plan is to build something with a 12 Volt(s) power supply because it would take longer to drain the batterie(s) (tell me if I am incorrect).

I am planning on building something almost like this (the type of battery on the diagram isn't relevant I could change it any time to a different type):



-- Andrie :P
Last edited by Andrie on Wed Oct 16, 2013 11:00 am, edited 4 times in total.

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Re: Solarpanel and Batteries

Postby cottonpickers » Fri Oct 11, 2013 7:31 pm

Andrie: The voltage should not influence the time to drain. Think of a 6v lantern battery (lasts a long time) versus a 9v battery (doesn't last as long) Its really all about their capacity, not so much the voltage. You can get tiny 12v batteries for car alarm key fobs but they don't have the power to start a car even though they are 12v.

Basically you multiply the voltage with the capacity to get the total watt hours then compare to the amount of watts that get used up.

SO... a high capacity D cell that is rated at 8,000mah and is 1.2v holds about 9watt hours (math here is 8 x 1.2) compared to a 280mah 9v battery that powers my remote control car that only holds only about 2 watt hours (math here is 7.2v X 2.8)

The Raspberry pi uses up about 2watts per hour. So you could in theory run a Pi off a 9v battery for about an hour or from a D cell for about 4.5 hours. Of course you'd need to convert the voltage.

I'm not sure I'm explaining too well here :-) but when you convert to 5v that the pi needs, ultimately its the capacity in watts that counts (which is a combination of Voltage x mah) rather than just voltage. A simpler way is that its the size of the battery :-) So you could easily wire 8 cells together such that they basically gave 5v with twice the capacity of just 4 batteries.

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Re: Solarpanel and Batteries

Postby Andrie » Sat Oct 12, 2013 4:11 pm

Thanks for your feedback! So I should get some of these: , (what type would you recommend).

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Re: Solarpanel and Batteries

Postby cottonpickers » Sat Oct 12, 2013 4:47 pm

andrie: I would not get those as they are 2500ma each. This means they are basically AA batteries wrapped in a larger plastic sleeve :? Better is are these at 8,500mah http://za.rs-online.com/web/p/d-recharg ... s/6708753/ or perhaps get these and use with your AA batteries http://www.ebay.com/itm/4-Pcs-New-Cell- ... 2a1e83262f
If you have 12 batteries, you could be put 8 in those and use the other 4 in the pi holder -if it were me, I'd do that.

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Re: Solarpanel and Batteries

Postby cottonpickers » Sat Oct 12, 2013 4:48 pm

andrie: I would not get those as they are 2500ma each. This means they are basically AA batteries wrapped in a larger plastic sleeve :? Better is are these at 8,500mah http://za.rs-online.com/web/p/d-recharg ... s/6708753/ or perhaps get these and use with your AA batteries http://www.ebay.com/itm/4-Pcs-New-Cell- ... 2a1e83262f
If you have 12 batteries, you could be put 8 in those and use the other 4 in the pi holder -if it were me, I'd do that.

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Re: Solarpanel and Batteries

Postby Andrie » Sat Oct 12, 2013 4:48 pm

Sorry Cottonpickers, but my first post is not shown. In it I also added the a Arduino to the list of devices I would like to run from the solar-battery-thing(s) (I might build more than one). It (the Arduino) runs of 7 - 12 V what battery-power-supply must I then use?


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