solar/wind the Pi

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solar/wind the Pi

Postby demonmaestro » Thu Jun 27, 2013 8:56 am

Okay i am working on a complete stand alone project.

its going to be a cam that can be placed anywhere and anyone can view with there phone or what ever. Current Project log.<-Rpi forums

But im at another stand still. This needs to be a 24/7 constant operation ordeal.

This is what i have.

Small wind turbine -> 12v, 30w max, 2.5a
Solar pannel -> 12v, 20w max, 1.66a

everything needed to run off of battery
Internet -> 5v, 4.2w max, 840ma
RPi-> 5v, 3.5w max, 700ma

now i know i will need a charge controler will this work

I have been trying to keep this project under $200 usd that i am already over but this is just the prototype and i know i can do different on some of the things. Thats why i am coming here. Okay doky whats ya think? input?

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Re: solar/wind the Pi

Postby cottonpickers » Thu Jun 27, 2013 6:00 pm

demonmaestro: Looks like a nice project!

Firstly , Whatever you do is a good project :-) as you will learn and have fun. Some pointers below (but be aware that these are only my thoughts that you should decide to ignore or consider as you wish) I hope others will also chip in.

Your biggest challenge is the $200 cost....
I think you could use less power if youwanted, but it looks like you are using about 25ah a day so you'd need a 100ah 12v battery to keep you above the 50% depth of discharge that you should aim for (go lower and you damage lead acid)
Personally I'd get a Gel/AGM deep cycle if possible as they don't lose as much charge during inactivtiy OR I'd get a 'free' battery to play with and learn and save up for a proper Deep Cycle (the free option would keep your costs low but will be rubbish)
Get a good converter from 12v to 5v don't just rely on a cheap car usb port as they are likely innefficient. (or get a cheap car adapter to keep costs low and upgrade later)

Nice to have a combination of wind and solar. good idea. Get the wind generator up HIGH as that will Massively improve its efficiency.

I don't think I'd buy that controller. It has 3 stage charging which is good :-) but it doesn't say what voltage it is charging to. Just says '12v nominal' Personally I'd want to know if its charging to 13.7v (bit low) 14.4v or 15v (bit high) or somewhere in between. Lead acid will slowly 'sulphate' if the voltage is low. Knowing what its doing is important. So I'd get a different one where it says what the end voltage is. Then you can read up on your battery what it needs and get them matched better.

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Re: solar/wind the Pi

Postby ForestBE » Fri Jun 28, 2013 8:18 pm

Dear demonmaestro,

I gave up on a 24/7 solar only plan because of limited battery options to bridge maybe a week or even 2 of bad weather.
Why do you count 700 mA for the Pi (a model B?)? If you can use a model A you will get away with less than half of this figure.
I do not know your internet option (3G?) again high assumptions. You mention that anyone should be able to connect to it with a (smart?) phone. Thus Wifi should be sufficient. Pi A and WiFi should go for less than 500 mA (maybe calculate with 600 mA to take additional circuits into account - e.g. an RTC).

Just some thoughts,


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