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DIY - Watertight x4 AA Solar Battery Charger (pics and info)

Discussion in 'Do-It-Yourself & Gear Modifications' started by bruner, Feb 22, 2007.

  1. bruner

    bruner Loaded Pockets

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    Introduction

    I know very little about electronics aside from how to shock myself... Therefore, I credit G. Forrest Cook and his WEBSITE for providing me with the general instructions for the electrical assembly. Thank you Mr. Cook! I also got some charging time estimates from a few CPF members on THIS thread. Thank you CPF members! Now, on to the project.

    The Watertight Box

    [​IMG] [​IMG] [​IMG]
    I found these watertight containers at my local Gander Mountain for about $10. They are intended for carrying fly fishing hooks. I removed the grey foam that they came with to make space for the charger parts.

    The Solar Cell

    [​IMG] [​IMG] [​IMG]
    Although Mr. Cook did not use this solar cell on his project, he did suggest that it would be a very good candidate. I am referring to the Electronix Express model #08SLC07, which is 5V 60mA solar cell shown toward the bottom on this Product Page. Two nice features about this solar cell are that it is laminated to a PC board and includes a diode. The diode prevents the batteries from discharging back into the cell when in the dark. As you can see in the third photo, I have used a double layer of double-sided foam tape which will be used to attach the cell to the inside lid of the box. It was necessary to use a double layer of the foam tape so that the cell would set high enough off of the mounting surface to provide room for the diode, the terminals and the wires.

    The Battery Holders & Batteries

    [​IMG] [​IMG]
    For battery holders, go to RadioShack. I think they were less than $1 each. For batteries, I needed to meet the minimum purchase of $20 at Electronix Express, so I bought the batteries through them at $3.50 each. Yes, I know I probably got raped at that price, but it did help meet the minimum purchase requirement. The plus side of that is that these are low capacity nicad batteries rated at 1.2V 700mA. According to the folks over at CPF it is a reasonable estimate that, with the solar cell I chose, it would take approximately 12 hours of solid sunlight to charge 2 AA batteries. If I were to use high capacity 2500 mA nimh, it would take approximately 42 hours of solid sunlight to charge 2 AA batteries. My charger is set up to charge either 2 AA batteries or 4 AA batteries at the same time. If you were to charge 4 AA batteries at the same time, then you could double those time estimates... My thinking is that one would most likely be "topping off" batteries that are "not quite dead" as opposed to charging batteries from a completely dead state, so I feel that this charger is adequate for my needs. Please note in the first photo that the battery holders from RadioShack do not include the double-sided foam tape. That was added by me for attachment to the interior of the bottom of the box.

    The Schematic Diagram

    [​IMG]

    Don't ask, I barely speak the language... But, the diagram should be accurate.

    The Final Product

    [​IMG]
    It folds shut without any danger of crimping any wires and it's watertight. The batteries remain in thier current state of charge untill needed. I'm happy with it and I'll try to answer any questions that you might have. Just keep in mind that I'm not electronicaly inclined.

    Thanks for looking,
    Dan

    PS. Here's a sneak peak at all the other "modular components" of my bug out bag made from the same watertight boxes from Gander Mountain.

    [​IMG] [​IMG]
     
  2. bruner

    bruner Loaded Pockets

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    As of 9am EST 02/23/07, it appears that some of my images are not loading. It looks like ImageShack is having some trouble... They worked fine last night...

    Dan
     
  3. greenLED

    greenLED Empty Pockets

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    It's working on my end.

    Very nice build, bruner!

    O0
     
  4. Starcruiser1229

    Starcruiser1229 Loaded Pockets

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    Cool project! I count 12 pictures - how many are there supposed to be? If you are still having a problem, let me know - I have a paid hosting server that I can use to host them for you if you need me to. I really like this project - it must be a lot more cost effective than buying one, and it looks really good, plus it is waterproof, and it matches the rest of your gear!
    Patrick
     
  5. bruner

    bruner Loaded Pockets

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    Thanks guys,

    Yep, there are a total of 12 images and it looks like they are showing up now. Imageshack must have been busy or doing some maintenance or something.

    There are other chargers out there for less money, but like Starcruiser1229 said, I like that it's waterproof and matches my other gear ;)

    Dan
     
  6. dinoadventures

    dinoadventures Empty Pockets

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    Very cool, Dan!

    What's the total cost for this project?
     
  7. bruner

    bruner Loaded Pockets

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    Dino,

    Let's see, generally speaking, I spent:

    $10 for box
    $14 for batteries
    $4 for battery holders
    $8 for solar cell

    I allready had the double-sided foam tape, so the total for me was about $36.

    What killed me was getting that solar cell from Eletronix Express... Their minimum order was $20, so I threw some money out the window buying my rechargeable nicad batteries from them to meet the minimum...

    Like I said, there are other chargers out there for less money, but this is what I really wanted.

    Dan
     
  8. Cordless

    Cordless Empty Pockets

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    Bruner, thats a excellent post in all respects. O0 Thanks for taking the time to post it. And thanks for the links to F.Cook's solar circuits pages.
     
  9. kmcrawford111

    kmcrawford111 Empty Pockets

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    Very nice project! I'm always happy to see solar power get used. I hope it becomes a much bigger part of our lives in time, and things are looking bright (pun not intended) so far.
     
  10. Priestly

    Priestly Loaded Pockets

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    Excellent project and an excellent post, Bruner! :thumbsup:
     
  11. KydexSecrets

    KydexSecrets Empty Pockets

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    Whats your charge time on a sunny day? Looks like a great project! time to heat up the ol soldering iron!

    -KS
    Kydex Secrets
     
  12. bruner

    bruner Loaded Pockets

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    I haven't tested it yet myself...

    Those charge times are all theoretical and based on full exposure to sun.

    Dan
     
  13. Bernout

    Bernout Empty Pockets

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    Would be great to see a transparent version or one with a window, and the solar cells facing outward -- allowing the batts to be charged in a watertight condition, like on a boat while fishing. Nice work!
     
  14. jag-engr
    • Administrator

    jag-engr Semper Bufo!
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    I believe that the Otterbox 1000 or 2000 would meet these criteria. They are available with one side clear. I think that Pelican also makes something similar. I think Bruner may be concerned about cells overcharging (and rightfully so) if they are exposed to unchecked sunlight.
     
  15. bruner

    bruner Loaded Pockets

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    jag-engr,

    I had not thought of that myself, but good point.

    :thumbsup:

    Dan
     
  16. snidera

    snidera Loaded Pockets

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    A switch would negate that. A simple regulating circuit would be even better. It's all in how complicated you want it to be. There are solar cells taht can produce more power in about the same size as those for not much more cost, but you'd need a more complex circuit. This is a good application of KISS IMO.
     
  17. CootShooter

    CootShooter Loaded Pockets

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    Have we seen any charge time input yet?
     
  18. Itamimasu

    Itamimasu Loaded Pockets

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    This is awesome.
    I have been meaning to make one of these for awhile. I am going to try it with some solar panels out of the patio lights you see all over.
     
  19. tndiver13

    tndiver13 Loaded Pockets

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    Great build. Nice project . ;D