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Building a Lithium Ion Battery Pack. Need help.

Discussion in 'Electronic Design' started by Bighiller, Mar 30, 2009.

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  1. Bighiller

    Bighiller Guest

    My goal is this:

    To be able to power a 21W HID bulb for 3hours using AA sized lithium-
    ion batteries and to charge them using one charger. Basically I am
    building an underwater canister dive light, but I'm not 100% on the
    battery pack and how to wire it.

    I understand I can buy a bunch of batteries at ~3.7V each, but I need
    to know how to wire them up to the PCM and other such niceties. If
    someone could point me in the right direction, that would be
    excellent!

    Let me know if anyone could tell me what I'll need to make this so.

    Thanks,
     
  2. Guest

    And you wanna trust your life to the low life yahoos on this group!?
    Never heard of AA 3.7V lithium ion cells. You got a link?
    http://www.greenbatteries.com/libafa.html#Li-ion in AA
    "Are Lithium Ion batteries available in standard sizes like AA , C or
    D cell size?
    No, Lithium-ion batteries are not available in standard sizes. "
    I'd point you in the direction of a diving supply store. And of you
    still want to build something like this yourself, I'd point you to a
    stretcher in the back of the truck driven by the men with the
    butterfly nets.
     
  3. PeterD

    PeterD Guest

    A 63 Watt hour AA sized battery would be quite a trick. You could go
    voltage I suppose, and have a *lot* of batteries, but they why limit
    yourself to AA sizes? That said, there is no such thing as a AA sized
    lithium battery anyway.
     
  4. Guest

    He is probably talking about 18650 cells. They are slightly longer and
    wider in diameter than AA cells.

    Lithium-ion batteries require more attention to safety than nicad or
    nimh.
     
  5. James Arthur

    James Arthur Guest

  6. James Arthur

    James Arthur Guest

    Confining a large lithium-ion pack in a pressure-tight
    container is DANGEROUS. Be careful.

    A safety vent's a good idea.

    Best of luck,
    James Arthur
     
  7. Benj

    Benj Guest

    Absolutely. My camera takes them. They are nifty gadgets! The
    batteries have a tiny circuit board built right in the end that
    handles all the electronic sensing and charging folerol for Li-ion
    batteries too.
     
  8. TheM

    TheM Guest

    I don't get this:
    http://www.ssp.ie/images/CHARGE.jpg
    "Through Case Charging - Reduced possibility of leakage due to seal damage"

    It looks terminals are in contact with sea water.

    M
     
  9. IanM

    IanM Guest

    I downloaded the data sheet for JJJ-LC14500 and it did not appear to
    "handles all the electronic sensing and charging folerol for Li-ion
    batteries too"
     
  10. Bighiller

    Bighiller Guest

    That's a nice thing to say. And useful too.
    Buddy, just keep your useless comment to yourself. You know jack and
    squat about what I am doing and you just want to seem like you know
    something....which is doubtful.

    Good luck with that.

    Well, thanks for the useless comments, they've made all our lives
    better.
     
  11. Bighiller

    Bighiller Guest

    I've check batteryspace.com and they have A LOT of lithium ion
    batteries and chargers, but I can't make out exactly what I need. It's
    a matter of wiring the batteries together and getting the right
    charger. As for the size, well I don't really care, so long as they
    fit into a 2"x~12" PVC tube (roughly).
     
  12. Bighiller

    Bighiller Guest

    Yeah, I think I was.
    This is understand, hence my posting.

    They will be in a sealed container, but not permanently sealed. It's a
    canister dive light, using PVC, proper O-rings, etc. SS latches hold
    the top on making an air-tight seal.
     
  13. Bighiller

    Bighiller Guest

    I understand that, but it shouldn't be a problem as the pack would
    only be sealed for ~2hrs MAX. It's a dive light and I don't plan on
    any LOOOOOOOONG dives.
     
  14. Jim Yanik

    Jim Yanik Guest

    how do you recharge it then? the diode would block charging current.
     
  15. James Arthur

    James Arthur Guest

    CONNECTION: several cells in series, or series-parallel, to
    get the voltage the HID needs.

    SAFETY: you need battery pack electronics, thermal switch, + a
    one-way valve (vent) for the containing vessel.

    The battery pack electronics protects each cell in the series
    pack against reverse voltage, overdischarge, overcharging, and
    the entire thing against short-circuit. The thermal switch
    (PTC, positive temp. coefficient thermistor) is built-in to
    many LiIon cells' anode contact. It's a back-up short-circuit
    protector.

    Numerous vendors offer pack electronics configured for common
    pack voltages.

    CHARGER: current-limited to C/2, voltage-limited to 4.15v per cell.

    You might consider the 18650 size cells--they're the standard, bigger,
    stronger, and cheaper. 14500's not so much.

    The dangers are many--LiIons will vent with flame if abused, sometimes
    not for hours or days after the insult. I don't know how they'll like
    being pressurized.

    You need the one-way safety vent. They're common, and cheap.
    Otherwise, you're making a pipe bomb.

    HTH,
    James Arthur
     
  16. Bighiller

    Bighiller Guest

    The canister will only be air-tight with no-venting as I am in the
    water (max ~1hr). The pressure inside the canister will remain at
    1bar, while the outside pressure on the canister will max at about
    4bar. The battery pack will be housed in a air-tight/water-tight
    (both) canister for the dive. The battery pack will be contained with
    heat shrink wrapping. The batteries will NEVER (as long as I can help
    it) come in contact with water. As for the venting, please, if you
    could, explain why I need to vent this canister? The battery pack will
    stay in there only while on my dive and it's not likely to create an
    explosion underwater. When you say vent, do you mean out of the
    battery pack or out of the canister?
     
  17. James Arthur

    James Arthur Guest

    I mean that if and when the battery pack catches on fire, a vent
    will keep it from killing you. The excess pressure has to have
    an escape all the way to the atmosphere, otherwise it'll build
    up, burst and shred most any container. That throws shrapnel,
    fire, and incandescent burning metal everywhere inside your car,
    boat, or backpack.

    It doesn't happen often, but it happens.

    Vents are common in flashlights, even dive lights IIRC. They
    keep external pressure and water out, but let internal pressure
    escape.

    One method uses a silicone rubber plug--it'll pop out under
    overpressure conditions. Another is a simple seal arrangement
    that compresses and seals tighter under sea pressure, but
    which lets internal pressure out. AKA "check valve."


    (View in Courier font)

    battery
    /
    plug | .--..--. |
    --> (== | || | |
    | | || | |
    | | || | | <~~container
    | '--''--' |
    '----------'

    Cheers,
    James Arthur
     
  18. Bighiller

    Bighiller Guest

    That I understand. I think, so long as it doesn't pop off, I'd could
    integrate a check valve. Just would suck if it popped off underwater
    and then water seeped in an made a bigger mess. What I am building is
    similar to one of these:

    http://www.halcyon.net/?q=lights/explorer

    I prefer lithium-ion as they last longer and an HID for the quality
    and quantity of light. Simply need a battery setup that will fit into
    a canister like the one on their page....

    BTW, thanks for your input James!!!
     
  19. James Arthur

    James Arthur Guest

    Dunno. Soiled wetsuit, that's for sure.

    James Arthur
     
  20. Bighiller

    Bighiller Guest

    Soiled dry suit! :)

    There is a guy that builds these things and his says that it's not as
    bad as was expected when lithium-ion batteries were first considered...
     
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