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There are numerous topics out there about powering Raspis from batteries or from solar or just making a waterproof enclosure... But I'm a programmer, not an electrician. I would end up plugging the flux capacitor into the manifold, blowing up the matrix. I think we can all agree: Nobody wants that.

Is there anything out there for sale that does all three?

Long story short, I want to stick a Pi in with our chickens so I can see when they're laying and when they're pecking at their eggs. The hutch is pretty waterproof but I wouldn't trust it for a moment. There's also no mains there.

I'd be looking for something that can survive the elements, contains its own regulated power pack for the pi, a camera and a wifi dongle to run 24/7 and has a way to charge it that doesn't involve any mains power. Ideally a solar trickle charge in the daytime via a fat panel on top of the hutch.

Does such a thing exist?

Edit: The comments are getting a bit tangled as people go off on tangents about the various parts of this problem. I am not adverse to breaking this into smaller segments but they do have to be geared towards somebody who doesn't understand the difference between Amperes, ohms, watts and volts.

So let's break this into two things

  • Power and charging

    What about a 44Ah 12V silver/lead battery, solar panel and a cigar-lighter socket with a USB adaptor? Is there any chance the Pi's going to get fried sitting behind that sort of circuit? How long is 44Ah@12V going to last? What sort of panel size am I going to need to keep it going indefinitely (consider the unearthly grey of UK winter)?

  • Enclosure

    Is a little IP66 box going to do the job? It's meant for outdoor junctions but the Pi will fit in it and all its "inputs" are rubberised silicone seals.

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  • I am aware of 100W kits like this but they're £500 (eep!) for way too much power. I'll run a DC line out to the chickens before I spend that much. Edit: for similar prices you can buy solar-powered IP-cams - but again, way too much money.
    – Oli
    Commented May 14, 2013 at 10:20
  • There seem to be solar panels with chargers for car batteries: batterystuff.com/solar-chargers/SP-5.html. @XAleXOwnZX mentioned that the car battery may last the Pi a week at least. If there's sun, you can recharge it using the above panel. Sounds like you may get away with 200 USD for the panel with charger, a battery plus you need a small 12V-5V adaptor.
    – Arne
    Commented May 15, 2013 at 9:58
  • @Arne (24 hours * 0.7A) / (8h * 350mA) * $139 = $834 just to make it even. How did you arrive to the 200 USD figure?
    – lenik
    Commented May 15, 2013 at 10:30
  • Yeah, you're right. You need more than one panel to both power the Pi and charge the battery. However, if you are willing to charge the battery every couple of weeks using a conventional charger, you may need less panels. :)
    – Arne
    Commented May 15, 2013 at 12:57
  • The company above seems to have also bigger (and cheaper) panels: batterystuff.com/solar-chargers/bsp22watt.html -- Those decrease charging times for a lead battery significantly. 1.2A is I think still a pretty valid charging current for lead batteries.
    – Arne
    Commented May 15, 2013 at 13:00

1 Answer 1

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Long story short -- there are a few waterproofs, you may even make your own using an acrylic sheet and a bit of glue. But there's no real solution for the solar battery power, the reliable solution that survive at least a few rainy days will include the truckload of batteries and dozens of square feet of the solar panels, driving the cost into the thousands.

Your raspberry consumes about 0.7a * 5v = 3.5W every hour. Two rainy days and you need 48 * 3.5 = 170Wt-hour, that is about 4 of average (Lead-Acid 6V 7.2Ah) batteries combined. Factor into this the fact that battery does not like to get totally empty, that results in 6-8 pack, just to cover 2 days.

To recharge this monster in just 8 hours (an average light day) you'll need about several amps of power, and most DIY solar panels provide only about 100-150mA, so you'll need plenty of them. And don't forget the charger -- the very important part, that will monitor your battery status and avoid overcharging, do the trickle charging and other interesting things.

From my point of view, you will need an internet connection to see your chicken, why don't you just lay another +5V wire along with the network cable?

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  • To the last part: I was planning on Wifi. Chicken hutch is 50M from the house but has line of sight to the router.
    – Oli
    Commented May 14, 2013 at 15:39
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    wireless == power, you'll need an even bigger battery/solar panel for that.
    – lenik
    Commented May 14, 2013 at 16:00
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    0.7a * 5v = 3.5W every hour: false. Watts are energy per second (1 W = 1 J/s). It would consume 3.5 Joules (J) per second, or 12,600 Joules per hour. The distinction should be made between "Watt Hour" (WH) and "Watt every Hour". The first means an amount of energy consumed by a device that draws 1 Watt of power for one hour (1 Wh = 3,600J). The latter isn't of physical significance.
    – Alexander
    Commented May 15, 2013 at 5:33
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    @BobT, car batteries run@12v, so if that were dropped down by a buck converter (switching power supply) as opposed to a regular (inefficient) linear power regulatory it would last much longer. A linear (typical) regulator just dissipates the voltage drop into heat [Heat output (W) = Current (A) * Voltage drop (v)], whereas a switching power supply would have a >90% efficiency (although it varies with other factors). The input of the PS would draw 12V, but much less current, and output 5V at a higher current than the input. This would over double the battery life, bumping it to almost 2 weeks.
    – Alexander
    Commented May 15, 2013 at 5:45
  • 2
    @lenik It's nothing personal, but many people depend on SE for data. The majority of users of this sub site are likely just linux enthusiasts and not electrical engineers, so giving them reliable information is of utmost importance.
    – Alexander
    Commented May 15, 2013 at 5:46

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