Portable D Battery USB Charger

[Cannon101]

I noticed that D batteries have around 8000-12000 mAH per battery while most AAs have under 1800 mAH, and that alot of portable usb chargers on the market that I have found are only AA and 9-volt and that seems to be even worse. I was wondering if anyone has a guide or ideas on how to build a D battery pack, I know i will need to step down to 5v and a female usb, but the idea is that with 3 batteries I could run a little over 30000mAH or 30 AH, which with the added usb devices could run my Raspberry Pi for up to 39-42 hours while camping. The point being that by carrying batteries and this pack I could camp for up to a week or two at a time and still get my work done with a 3g card, I will make two of there probably to run a micro LCD monitor. Ideas? Sorry for the trouble, just could get a good idea going.

 

[alyoshka]

Since the idea is camping and power.... have you thought about one of these....
http://www.voltaicsystems.com/offgrid.shtml
they've already started making such stuff it's be worth the try.

 

[Cannon101]

Since the idea is camping and power.... have you thought about one of these....
http://www.voltaicsystems.com/offgrid.shtml
they've already started making such stuff it's be worth the try.

I have seen a few of those, however, I already have a bag, and I'm looking to make something very compact, and cheap. I'm fairly certain I could make this design for less than $20 with the right help. Not to mention all of those bags I have seen require sunlight, usually 1 hour equals 30-50 minutes of battery time, and since it is usually is dark or rainy (it will also soon start snowing heavily) most of the time and I'd be moving during the day time through thick trees it wouldn't have time to sufficiently charge enough to do my required daily work.

 

[alyoshka]

Since you're going to be walking a lot have you thought about the shake and charge ones??.... since you are in to making something, like I call it, Creative Engineering, here's a little something that you can break down and put to good use in your setup
http://www.amazon.com/Shake-Flashlight-Batteries-Simply-Recharge/dp/B000637LTY
http://discovercircuits.com/H-Corner/shake-chgr.htm

Even this is a great idea....http://en.wikipedia.org/wiki/Mechanically_powered_flashlight
I'd have hooked up a bicycle Dynamo to one of these and got it to gimme some usable current.

 

[Cannon101]

Those are kind of cool, but I'm mostly doing this so that I can come up with a nice guide for myself and others. I already have a solar AA charger that lasts around 4 hours, but d batteries are so cheap that if I could make this work then you could potentially spend less than $5 per trip to have your small computer run for up to 80 hours continually, not to mention, I like a good project =).
Also, I saw you would have to shake one of those for 30 seconds to only power a small LED for 5-7 minutes, but this would have to be able to store hours of battery life while not over exerting yourself when already carrying an 60-80 lb bad for hours.

 

[alyoshka]

Is that your mail that you posted there?
Get rid of the link....PLS
Just copy the content without the to's and from's and paste it here....

 

[Cannon101]

oops, i meant to, copied link from wrong window, sorry

 

[Recycled]

You suggest 2 batteries, each at 1.5V nominal, each holding 10,000mAH=10AH.
2x1.5Vx10AH=30WH.

I suggest 3 lithium 18650 batteries, each at 3.7V nominal, each holding 3,400mAH=3.4AH
3x3.7Vx3.4AH=37.74WH

I'd go with some 18650 lithium cells. Search for "18650 usb charger" on eBay (for junk cells) or on www.FastTech.com (for quality cells.) They are available with 2, 3, 4, or more cells. Replace the cells with good quality Panasonics or Sanyos. As a plus, lithium cells are lighter and more resistant to cold temperatures than are alkaline cells.

Here's one preassembled for $31.27 + S/H: http://www.fasttech.com/products/0/10004458/1341103-xinbo-1-1-5a-3-18650-single-usb-output-mobile

Note: I get no compensation from FastTech. I have had good experiences with them after lousy experiences with sold-on-eBay cells.

 

[Cannon101]

oho, thank you very much sir, I had forgotten this project until today. Thank you for the input

 

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