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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.

Oli
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  • I am aware of [100W kits like this](http://www.camsecure.co.uk/SolarPanel.html) 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](http://www.solcam.co.uk/products.html) - but again, way too much money. – Oli May 14 '13 at 10:20
  • There seem to be solar panels with chargers for car batteries: http://www.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 May 15 '13 at 09:58
  • @Arne (24 hours * 0.7A) / (8h * 350mA) * $139 = $834 just to make it even. How did you arrive to the 200 USD figure? – lenik May 15 '13 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 May 15 '13 at 12:57
  • The company above seems to have also bigger (and cheaper) panels: http://www.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 May 15 '13 at 13:00
  • @Arne On that tangent, for just over £100 you can buy a panel that claims to kick out 100W at 12V (over 8A?). This question has never been about whether or not you can buy the parts - it's about if there's something idiot proof that does it all for you. I'm not an electrician or a physicist. The finer points of electrical engineering are Greek to me. That's a lie, I actually know more Greek than I do electrical engineering. – Oli May 15 '13 at 13:07

1 Answers1

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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?

lenik
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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 May 14 '13 at 15:39
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    wireless == power, you'll need an even bigger battery/solar panel for that. – lenik May 14 '13 at 16:00
  • Er... Conservatively, a car battery's capacity is ~.5Kw/hours from full charge to discharge (40 amps x 12 volts) depending on the battery. This is sufficient to power your 3.5 watt Raspberry for 142 hours, or 6 days. – BobT May 14 '13 at 16:50
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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 May 15 '13 at 05:33
  • @XAleXOwnZX would you mind to check my grammer and punctiation as well? thanks. – lenik May 15 '13 at 05:39
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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 May 15 '13 at 05:45
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    @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 May 15 '13 at 05:46
  • @XAleXOwnZX, I was only commenting on the capacity of the battery as a reply to lenik's (original) erroneous analysis.. Of course efficiency of the conversion to 5V will make a difference. – BobT May 15 '13 at 15:08
  • I understand, I'm just adding on. Most beginners use linear regulators and lose a lot of battery life they could have otherwise had with a switch mode power supply – Alexander May 15 '13 at 22:04
  • Hundreds of dollars, yes. Thousands, no. A hundred-watt solar panel will run about $100, a 75 AH marine deep-cycle battery will run about $100, and a 30-amp charge controller will run you another $100. Add in somebody's 12V to USB charger ($20) and a waterproof case ($50), and you've got something that's ridiculously overpowered for under $400. – Mark Jul 17 '17 at 20:41