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Copper pipe for cross connections

Discussion in 'Home Power and Microgeneration' started by 'Captain' Kirk DeHaan, Mar 2, 2004.

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  1. I'm planning on using copper pipe, flatten of course, to interconnect
    the 6 volt cells in my 12 volt battery bank. The flexible cables get
    in the way of the caps. I will still use flexible cables to
    interconnect the pairs in parallel. These are L16's. What pipe
    diameter is sufficient?


    "Moe, Larry, the cheese!", Curly
  2. Bob Peterson

    Bob Peterson Guest

    depends entirely on the current it is required to carry.
  3. Ecnerwal

    Ecnerwal Guest

    And the wall-thickness of the pipe - they are not all the same.
  4. Bughunter

    Bughunter Guest

  5. My brain wants to say there's something about rigid interbattery
    connections that's tough on battery posts, but I can't really
    remember. Maybe something about inherent stresses or small battery
    movements being clamped down?
  6. Sounds like a plan to me. I'll see if the local steel recycling
    outfit has any. The handle all metals.


    "Moe, Larry, the cheese!", Curly
  7. More than adequate considering I'm using 8 L16's in series-parallel.
    The inverter is 2500w and I rarely get to 1500w and that's when using
    a skill saw, etc.

    My calc's say that would be about 31 amps on each pair. Well below
    what you stated.


    "Moe, Larry, the cheese!", Curly

  8. Perhaps a slightly oversized hole that would allow some expansion or
    movement. But then if it's capable of moving you probably have a
    reduction in conductivity. I can't believe though it would be that
    much stress as the connection is angled and the span is only about 6


    "Moe, Larry, the cheese!", Curly
  9. Bob Adkins

    Bob Adkins Guest

    A good educated guess would be 3/8 for up to 200A, and 1/2 for up to 500A.
    Of course you need to make sure the pipe is not getting hot. If so, just go
    up a size.

    Why not just get copper flat stock? some 1/8 x 1" would carry a hell of a
    lot of current, and you wouldn't have to do all that flattening.

    Don't forget to get some nice 1/4 or 5/16 copper or brass bolts, nuts, and
    washers while you're at it.


    Remove "kins" from address to reply.

  10. Found some 1/2" x 1/4" stock for .38 a foot. Should be sufficient for
    my needs. Currently using #2 cable for interconnect.


    "Moe, Larry, the cheese!", Curly
  11. Yabut the cracks would be parallel to the current flow, so would not
    effect it. Not that you'd want cracks, but it's not going to effect
    your ampacity. You probably will have more concern about your
    home-made battery terminals than the copper between them...
  12. Bob Adkins

    Bob Adkins Guest

    Oh yea! That'll carry some serious current! Good price, too!


    Remove "kins" from address to reply.
  13. I would reconsider the pipe - it is RIGID and any
    expansion/contraction cam break the posts out of the batteries. Rather
    use a few copper ribbons cut from copper flashing and bent to allow
    some movement. Broken links inside batteries can cause battery
    explsions. Don't ask how I know - suffice it to say I used sheet
    copper ribbons to connect the batteries in my electrified Fiat.

  14. But my batteries will not be moving. Expansion will be at a minimum as
    the ambient temp is within 5 degrees year round in the room.


    "Moe, Larry, the cheese!", Curly
  15. I have a bank of Absolyte II AGM's that I have built my own links
    out of 1/2" copper tubing flattened on the ends and drilled with
    1/4 inch holes. These links replaced the original links that were
    solderplatted copper 1/2"X 1/8"X 6". This bank runs my ISP Servers,
    Routers, WiFi Access Points, and Networking Systems, for
    here in the bush of Alaska. I have a Trace U2624 that provides the
    Inverter/Charger for this bank and is AC powered from a 20Kw Diesel
    Genset, that runs 10 hours a day. (7am to noon, and 5 Pm to 10 Pm)
    Just enough to keep the freezers cold and the inverter batteries topped

    Copper tubing works very well for these battery links, on this
    800Amp/hour bank.

    Bruce in alaska
  16. It's up to you - but generally "forwarned is forarmed". Just the
    cyclic heating and cooling of the batteries with charge and discharge
    CAN cause problems. I would NEVER advise it.
  17. Graig Pearen

    Graig Pearen Guest

    ALL the telcos have been using busbars between cells "forever" - well over 50 years at least. It
    never causes a problem in a heated building and these strings are usually 12 cells in a row. The big
    cells are at least 18 inches square so that is a lot of copper lined up end to end. Even in poorly
    heated and non-airconditioned huts, I've never seen a problem in my 40 years in the business.


  18. The expansion I would see appears extremely insignificant.


    "Moe, Larry, the cheese!", Curly
  19. daestrom

    daestrom Guest

    The vibration and movement in an 'electrified Fiat' is probably more than
    what we're going to experience in any permanent setup.

    But for the record, even very large batteries like the ones we used on
    submarines can be bolted with 'rigid' connections. The cells are wedged
    tightly together with wooden wedges, then the connections made up. We never
    had more than about 7 cells connected in a single row, but that was for
    magnetic field suppression. The 7 cells would be connected with eight
    pieces of lead-covered copper bus bar about 1 foot long. Each cell measured
    about 18" square with the negative posts on one side of one cell connected
    to the positive posts of the adjacent cell. After about six of seven cells
    in one row, the bus-bars would jump sideways to cell in the next row for
    about six cells. This formed adjacent loops that would cancel their
    magnetic fields (to foil magnetic mines).

    Despite all the 'angles and dangles' the boat would take on, we didn't have
    a problem with inter-cell connections working loose very much (did test them
    while doing test-discharges every month).

    P.S. For safety, we only used shortened, non-sparking (phosphor-bronze)
    tools in the battery well. Including a specially made torque wrench for
    making up bus-bar connections.
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