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

[cottonpickers]

As you likely know, the Raspberry Pi is advertised as being able to run off batteries, so I really had to have a go at making a battery pack. I also love all things solar and the idea of free power for my Pi was too enticing, so I was off to work.

The Pi runs off USB which according to the spec is 4.75v - 5.25v and can draw up to 700ma.

Often specs are over rated and I know that most USB ports on a computer are rated at 500ma so I'm guessing this is a conservative rating.


Anyway, I've now put together a solar charger suitable for the Pi. Take a look, and feel free to ask any questions, or go to the 'I want one!' section to buy one.

The panel is a 2 watt, 330ma panel. - I 've got a variety of other panels ranging from 200ma up to 1000ma that I could use, but this one seemed a nice match. I'm thinking of using a different shape one at similar current, as well as looking at putting together a 1000ma panel with 10,000ma D Cells
This should give really good runtimes while still being portable.
I really want to get it set up as a web server and perhaps even run this Forum using solar - don't see why it shouldn't be possible off a Pi.

[MacD]

Do you think you could run this 24x7??? perhaps if it wasnt' plugged in to a TV? I'm thinking of an outdoor project that probably wouldn't tax the Pi, but wondering if the batteries could run through the night? do you think thats possible?

[cottonpickers]

Not in the UK ! - It looks to be good for a good few hours, but it would never make it through the night. I'll take some readings this weekend on current so you can see what the Pi is using as it boots up and settles down. But I'm pretty sure it wouldn't idle all night on a set of AAs. However!!! I'm always looking to improve these, and will make a few different ones, so watch this space. One I'm definitely going to make is a 4x D cell model with larger panel I've got some 8000ma D cells here and will see what I can do with them. I reckon *this* could do the trick. Watch thise space!!

BTW, would you like to guess how a voltage the Pi can actually take before it gives in??? (and how high before the fuse kicks in?)

[TinTin]

BTW, would you like to guess how a voltage the Pi can actually take before it gives in??? (and how high before the fuse kicks in?)

Well USB Spec is supposed to be 4.75 - 5.25 so thats my guess

[TheWhiteDragon]

Hey CottonPickers,

great design and planning, do you reckon you could beef it up enough to power a screen as well ?
debating picking up a 3.5"/4.3" tft screen to display the pi's os ?

idea being a triangle shape case/base, Solar Panel on 1 side, screen on another side, and bottom being the base holding the pi.

something along this line for the screen.
http://www.ebay.co.uk/itm/4-3-TFT-LCD-D ... 326wt_1110

what do you reckon ?
my electronic skills are maxed out at changing a plug, lol

[cottonpickers]

TheWhiteDragon: Yes that should be pretty do-able. Just need to work out the currents!

That one you link to is 12v. I do have a Lithium power pack that is pretty small and will output 12v but I think you'd be better off getting a 5v / usb model. Something like this: http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... ink:top:en

This one has its own built in battery and could also be charged by the pi solar charger. I could add the lead to charge the nimh and tv at the same time.
It would take a while to charge both this and the batteries with this panel though. I would suggest a larger panel unless you don't mind a slow charge time. I think it would take an additional 8 hours to charge the TV. But once full, you'd still get around 3 hours usage of PI with T
There are now some UK Freeview Model with inbuilt battery and 5V charging just ensure its 5v or USB in and has an AV-IN

BTW I doubt the chinese one off eBay would pick up UK HD TV I image it would be USA or Japanese TV only - but I could be wrong. If you want any help with putting something together let me know. Also, I'm interesting in how you might use it??

Here's the promised current graph that the Pi uses:


and interesting the Pi will go LOWER than 4v and still work fine . (Perhaps no surprise as most of the circuitry is actually 3.3v... but there you go!)

[TheWhiteDragon]

lol, great work cottonpickers

i have ordered the tv unit, but chinese delivery will prolly take about a month to arrive..
would you be able to sling a larger panel and an additional charging point together on your existing model ?
any idea on the extra cost ?

[cottonpickers]

Let me know what size you are after. Can do a 450ma, 700ma, 800ma or 1000ma panel. If you need an extra charging point I can put a USB socket as well as the micro USB lead. Extra cost would be about £10

[TheWhiteDragon]

if anyone else is planning this kinda setup i'd recommend Gittex37 for the screen above, price isnt bad for UK, and the seller is fairly open and host in explaining that obviously you cant use this as a proper tv in the UK.
though as its only displaying the Pi thats not a problem.....

http://myworld.ebay.co.uk/gittex37?ssPa ... AQ:GB:1181

[TheWhiteDragon]

Let me know what size you are after. Can do a 450ma, 700ma, 800ma or 1000ma panel. If you need an extra charging point I can put a USB socket as well as the micro USB lead. Extra cost would be about £10

hi cottonpickers,

which would you say would be the best size panel ?
the extra usb socket will be good though.