AA & 9V battery short circuit current

Discussion in 'Electronic Design' started by Robert, Oct 15, 2008.

  1. Robert

    Robert Guest

    Hello everyone,

    A battery powered product is headed for “intrinsically safe” certification.
    The main test documented in prior certificates uses the open circuit
    voltage and short circuit current from the power source to see if an
    explosive mixture of gases can be ignited. The circuit capacitance is
    placed across the combination of a bench supply and a limiting resistor for
    the test.

    I am looking for information on the short circuit current for 9V and AA
    batteries. This varies by manufacturer, model, and from battery to
    battery. I would also like to hear if anyone has ever tested small
    batteries for short circuit current.

    Have a good day,
    Robert
     
    Robert, Oct 15, 2008
    #1
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  2. Robert

    Jeff L Guest

    "Robert" <> wrote in message
    news:Xns9B386BC4996D5someonenowherecom@140.99.99.130...
    > Hello everyone,
    >
    > A battery powered product is headed for "intrinsically safe"

    certification.
    > The main test documented in prior certificates uses the open circuit
    > voltage and short circuit current from the power source to see if an
    > explosive mixture of gases can be ignited. The circuit capacitance is
    > placed across the combination of a bench supply and a limiting resistor

    for
    > the test.
    >
    > I am looking for information on the short circuit current for 9V and AA
    > batteries. This varies by manufacturer, model, and from battery to
    > battery. I would also like to hear if anyone has ever tested small
    > batteries for short circuit current.


    Short circuit current depends on a lot of things such as, in no particular
    order:
    - state of charge,
    - temperature,
    - age of cell
    - Chemistry of cell
    - Brand of cell
    - Internal resistance
    - Length of time cell is sitting idle
    - Revision of cell
    - Terminal material and attachment method, internal and external
    - etc

    For example, NiCd AA's could produce 100+A for a short duration. Cheap Zinc
    based AA cells might produce a short circuit current of a few amps. A 9V
    battery short circuit current would likely be around an order of magnitude
    less.

    >
    > Have a good day,
    > Robert
     
    Jeff L, Oct 16, 2008
    #2
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  3. Robert

    Phil Allison Guest

    "Robert"
    >
    > I am looking for information on the short circuit current for 9V and AA
    > batteries. This varies by manufacturer, model, and from battery to
    > battery. I would also like to hear if anyone has ever tested small
    > batteries for short circuit current.
    >


    ** If you are after "worst case" values, then look up the figures for "
    internal resistance" for AA size NiMH cells and 9 volt NiMH batteries on
    their maker's sites.

    A few rechargeable AA cells in series will have no trouble setting plastic
    coated wires and PCB component & tracks on fire. Then explode themselves.

    Products using them are NOT safe unless there is no possible way the cells
    can be shorted and there is a fuse link or other current limiting device (
    ie polyswitch) in series with the battery supply.

    BTW: NiMH AA cells are sold all over the place now, so any product using
    "loose" cells can expect to wind up with them installed.


    ...... Phil
     
    Phil Allison, Oct 16, 2008
    #3
  4. Robert

    Robert Guest

    John Fields <> wrote in
    news::

    > On Wed, 15 Oct 2008 15:35:45 GMT, Robert <> wrote:
    >>
    >>I am looking for information on the short circuit current for 9V and
    >>AA batteries. This varies by manufacturer, model, and from battery to
    >>battery. I would also like to hear if anyone has ever tested small
    >>batteries for short circuit current.

    >
    > ---
    > Wouldn't the various manufacturers be the best sources for that data
    > and wouldn't it behoove you to make the short circuit current
    > measurements yourself instead of trusting someone else's data to be
    > good?
    >
    > JF


    Have not found anything on the manufacturers web sites.

    The only measurements that will cound are the ones that CSA perform.

    Hoping to work a bit smarter. My aplication is low current. If one brand
    or model tends to have a lower short circuit current, it would make
    acceptance testing less of a problem. As a department of one, there is
    more to do than will get done.

    Have a good day,
    Robert
     
    Robert, Oct 16, 2008
    #4
  5. Robert

    Phil Allison Guest

    "Robert"
    >
    >> Wouldn't the various manufacturers be the best sources for that data
    >> and wouldn't it behoove you to make the short circuit current
    >> measurements yourself instead of trusting someone else's data to be
    >> good?
    >>
    >> JF

    >
    > Have not found anything on the manufacturers web sites.



    ** Hey dope - if you simply divide the cell / battery voltage by the
    internal resistance figure - you have the max short circuit current.


    > The only measurements that will cound are the ones that CSA perform.



    ** This is utter bollocks.

    AA and 9 volt batteries are USER REPLACEABLE !!


    > Hoping to work a bit smarter. My aplication is low current. If one brand
    > or model tends to have a lower short circuit current, it would make
    > acceptance testing less of a problem. As a department of one, there is
    > more to do than will get done.



    ** This is utter bollocks.

    AA cells and 9 volt batteries are USER REPLACEABLE !!

    You MUST work with a worst case scenario.

    Means you MUST design you device to be safe despite the HUGE current
    available from AAs and the latest 9 volt types.



    ...... Phil
     
    Phil Allison, Oct 16, 2008
    #5
  6. On Oct 16, 2:10 pm, Robert <> wrote:
    > John Fields <> wrote innews::
    >
    > > On Wed, 15 Oct 2008 15:35:45 GMT, Robert <> wrote:

    >
    > >>I am looking for information on the short circuit current for 9V and
    > >>AA batteries. This varies by manufacturer, model, and from battery to
    > >>battery. I would also like to hear if anyone has ever tested small
    > >>batteries for short circuit current.

    >
    > > ---
    > > Wouldn't the various manufacturers be the best sources for that data
    > > and wouldn't it behoove you to make the short circuit current
    > > measurements yourself instead of trusting someone else's data to be
    > > good?

    >
    > > JF

    >
    > Have not found anything on the manufacturers web sites.


    It's there on the data sheet, it's called the internal resistance and
    cell voltage - add ohms law and you have the maximum short circuit
    current when the cell is fresh.

    You are designing a product and didn't know this??

    Dave.
     
    David L. Jones, Oct 16, 2008
    #6
  7. Robert

    Martin Brown Guest

    On Oct 16, 3:45 am, "Phil Allison" <> wrote:
    > "Robert"
    >
    > > I am looking for information on the short circuit current for 9V and AA
    > > batteries.  This varies by manufacturer, model, and from battery to
    > > battery.  I would also like to hear if anyone has ever tested small
    > > batteries for short circuit current.

    >
    > ** If you are after "worst case" values,  then look up the figures for "
    > internal resistance" for AA size NiMH cells and 9 volt NiMH batteries on
    > their maker's sites.
    >
    > A few rechargeable AA cells in series will have no trouble setting plastic
    > coated wires and PCB component & tracks on fire. Then explode themselves.


    A pair is more than enough to source 10+A (initally closer to a
    50-100A transient spark) for plenty long enough to reach red heat
    burning off wire insulation and PCB tracks. The chemistry starts to
    get out of hand pretty quickly when only the cells internal resistance
    is the limiting factor. Heat gases, boiling electrolyte, venting and
    then explosion releasing cell contents. Sanyo reckon 1.2v and 0.025
    ohm at so around 50A 1000Hz. I have seen higher initial instantaneous
    short circuit currents than that.

    http://www.eneloop.info/uploads/media/Datasheet_-_HR-3UTG_01.pdf

    The old Kodak DC-120 camera managed to draw 2A continuously from 4x AA
    cells in worst case of macro mode with flash enabled. Modern digital
    cameras are a lot more frugal although their power packs still pack
    quite a wallop.
    >
    > Products using them are NOT safe unless there is no possible way the cells
    > can be shorted and there is a fuse link or other current limiting device (
    > ie polyswitch) in series with the battery supply.


    Or better that a cell is used in a physically encapsulated way such
    that it cannot ever source a high current no matter what the external
    provovcation. The stuff I recall for flame proof areas also included
    armoured impact casing and devious mechanical interlocks to ensure
    that no-one could ever open one without the requisite servicing tool.
    >
    > BTW:   NiMH  AA cells are sold all over the place now, so any productusing
    > "loose" cells can expect to wind up with them installed.


    Yep. If it will fit then one day someone will do it. You also
    sometimes find AAA cells wrapped with cardboard to make up the
    diameter and extended with folded KitKat foil or even a mixture of
    different capacity cells which is another *really* bad practice. But
    the guy just wanted to get it working again and bodged around with
    what was in his toolbox. It is annoying that field engineers who
    should know better do these sort of things as a quick interim fix and
    then forget about them until something really bad happens (like the
    weakest cell dies horribly).

    I find the prospect of the OP designing something that is intended to
    be intrinsically safe in an explosive atmospher particularly scary in
    the light of his question here. Hopefully the testing authorities will
    do their job adequately unlike USPTO.

    Regards,
    Martin Brown
     
    Martin Brown, Oct 16, 2008
    #7
  8. Robert

    Phil Allison Guest

    "Martin Brown"
    "Phil Allison"

    > > I am looking for information on the short circuit current for 9V and AA
    > > batteries. This varies by manufacturer, model, and from battery to
    > > battery. I would also like to hear if anyone has ever tested small
    > > batteries for short circuit current.

    >
    > ** If you are after "worst case" values, then look up the figures for "
    > internal resistance" for AA size NiMH cells and 9 volt NiMH batteries on
    > their maker's sites.
    >
    > A few rechargeable AA cells in series will have no trouble setting plastic
    > coated wires and PCB component & tracks on fire. Then explode themselves.


    A pair is more than enough to source 10+A (initally closer to a
    50-100A transient spark) for plenty long enough to reach red heat
    burning off wire insulation and PCB tracks. The chemistry starts to
    get out of hand pretty quickly when only the cells internal resistance
    is the limiting factor. Heat gases, boiling electrolyte, venting and
    then explosion releasing cell contents. Sanyo reckon 1.2v and 0.025
    ohm at so around 50A 1000Hz. I have seen higher initial instantaneous
    short circuit currents than that.

    http://www.eneloop.info/uploads/media/Datasheet_-_HR-3UTG_01.pdf

    The old Kodak DC-120 camera managed to draw 2A continuously from 4x AA
    cells in worst case of macro mode with flash enabled. Modern digital
    cameras are a lot more frugal although their power packs still pack
    quite a wallop.
    >
    > Products using them are NOT safe unless there is no possible way the cells
    > can be shorted and there is a fuse link or other current limiting device (
    > ie polyswitch) in series with the battery supply.


    Or better that a cell is used in a physically encapsulated way such
    that it cannot ever source a high current no matter what the external
    provovcation. The stuff I recall for flame proof areas also included
    armoured impact casing and devious mechanical interlocks to ensure
    that no-one could ever open one without the requisite servicing tool.
    >
    > BTW: NiMH AA cells are sold all over the place now, so any product using
    > "loose" cells can expect to wind up with them installed.


    Yep. If it will fit then one day someone will do it. You also
    sometimes find AAA cells wrapped with cardboard to make up the
    diameter and extended with folded KitKat foil or even a mixture of
    different capacity cells which is another *really* bad practice. But
    the guy just wanted to get it working again and bodged around with
    what was in his toolbox. It is annoying that field engineers who
    should know better do these sort of things as a quick interim fix and
    then forget about them until something really bad happens (like the
    weakest cell dies horribly).

    I find the prospect of the OP designing something that is intended to
    be intrinsically safe in an explosive atmospher particularly scary in
    the light of his question here.


    ** The OP is an utter ASS.

    There is NO WAY a unit containing AA cells or a 9 volt battery will ever
    be allowed inside a potentially explosive environment. It will have to
    remain outside and be linked by an intrinsically safe interface to whatever
    sensor is involved.

    My comments were only about the danger that now plagues all devices that
    allow the user to replace the cells or battery with whatever will fit.

    Even a common old AA alkaline cell will explode if shorted ( ie by an ill
    designed battery compartment ) or if fitted in reverse in a series battery.



    ...... Phil
     
    Phil Allison, Oct 16, 2008
    #8
  9. Robert

    Robert Guest

    "Phil Allison" <> wrote in
    news::

    >
    > ** The OP is an utter ASS.
    >
    > There is NO WAY a unit containing AA cells or a 9 volt battery will
    > ever be allowed inside a potentially explosive environment. It will
    > have to remain outside and be linked by an intrinsically safe
    > interface to whatever sensor is involved.
    >


    Hello everyone,

    The signal to noise ratio from google groups is quite low this morning. It
    may be time to reconsider some sort of filtering. Having received usefull
    information from unlikely places tells me to resist just blocking all
    google groups posts.

    Is there a quick way of blocking all posts from google on XNews?

    The public records will show many such devices have been approved. The
    last approval testing on this product showed over 10 amps from some 9 Volt
    batteries. That unit passes. Factors include how fast and how much energy
    is released.

    'Anyone can speak Troll,' said Fred dismissively,
    'all you have to do is point and grunt.'
    "Harry Potter and the Goblet of Fire" - J.K. Rowling (2000)
     
    Robert, Oct 16, 2008
    #9
  10. Robert

    Phil Allison Guest

    "Robert the LIAR "
    > "Phil Allison"
    >>
    >> ** The OP is an utter ASS.
    >>
    >> There is NO WAY a unit containing AA cells or a 9 volt battery will
    >> ever be allowed inside a potentially explosive environment. It will
    >> have to remain outside and be linked by an intrinsically safe
    >> interface to whatever sensor is involved.
    >>

    >
    > Hello everyone,



    ** **** off - dickhead.


    > The public records will show many such devices have been approved.



    ** But not for use *within* the hazardous area.

    You LYING POS.



    ....... Phil
     
    Phil Allison, Oct 16, 2008
    #10
  11. Robert

    Robert Guest

    Google Groups,

    Please accept by sincere apologies. You were falsely accused.

    ------------------
    Phil,

    *plonk*
     
    Robert, Oct 17, 2008
    #11
  12. Robert

    Martin Brown Guest

    On Oct 16, 3:37 pm, Robert <> wrote:
    > "Phil Allison" <> wrote innews::
    >
    > > ** The OP is an utter ASS.

    >
    > > There is  NO WAY  a unit containing AA cells or a  9 volt batterywill
    > > ever be allowed inside a potentially explosive environment.  It will
    > > have to remain outside and be linked by an intrinsically safe
    > > interface to whatever sensor is involved.


    It would be allowed inside a truly FlameProof certified casing. How do
    you think electric miners lamps work?

    The point here is that an AA battery cell is not intrinsically safe.
    It can source way too much current and juicy sparks.

    Anything that might spark internally is generally expected to be able
    to cope with the worst case explosive mixture inside it being
    detonated without showing any external signs of leaking flame or
    sparks. The kit might or might not work properly after this test, but
    it must not become a source of ignition.

    > The signal to noise ratio from google groups is quite low this morning.  It
    > may be time to reconsider some sort of filtering.  Having received usefull
    > information from unlikely places tells me to resist just blocking all
    > google groups posts.  
    >
    > Is there a quick way of blocking all posts from google on XNews?


    I suggest you learn to read headers as well as about Ohms law V = IR.
    The manufacturuers specify V and R it is left as an excercise to the
    reader to compute I.
    >
    > The public records will show many such devices have been approved.  The
    > last approval testing on this product showed over 10 amps from some 9 Volt
    > batteries.  That unit passes.  Factors include how fast and how much energy
    > is released.


    Lets see an example of one of these mythical devices that has been
    declared intrinsically safe with a 10A 9v spark source available
    internally. When you are in an explosive atmosphere you do not want
    any calorific sparks at all. Even inductors are carefully RC snubbed
    to keep the stored energy from causing trouble.

    I think you are confusing FlameProof and Intrinsically safe
    designations. See
    http://www.britishtelephones.com/flp.htm
    for a brief introduction to the differences.

    > 'Anyone can speak Troll,' said Fred dismissively,
    > 'all you have to do is point and grunt.'
    > "Harry Potter and the Goblet of Fire" - J.K. Rowling (2000)


    I think you need to heed that advice.
    Be sure to video the testing it should be amusing to watch on U-Tube
    as your kit explodes.

    Regards,
    Martin Brown
     
    Martin Brown, Oct 17, 2008
    #12
  13. Robert

    Robert Guest

    "Paul Hovnanian P.E." <> wrote in
    news::

    > Robert wrote:
    >>
    >> John Fields <> wrote in
    >> news::
    >>
    >> > On Wed, 15 Oct 2008 15:35:45 GMT, Robert <>
    >> > wrote:
    >> >>
    >> >>I am looking for information on the short circuit current for 9V
    >> >>and AA batteries. This varies by manufacturer, model, and from
    >> >>battery to battery. I would also like to hear if anyone has ever
    >> >>tested small batteries for short circuit current.
    >> >
    >> > ---
    >> > Wouldn't the various manufacturers be the best sources for that
    >> > data and wouldn't it behoove you to make the short circuit current
    >> > measurements yourself instead of trusting someone else's data to be
    >> > good?
    >> >
    >> > JF

    >>
    >> Have not found anything on the manufacturers web sites.
    >>
    >> The only measurements that will cound are the ones that CSA perform.
    >>
    >> Hoping to work a bit smarter. My aplication is low current. If one
    >> brand or model tends to have a lower short circuit current, it would
    >> make acceptance testing less of a problem. As a department of one,
    >> there is more to do than will get done.

    >
    > Hmm. If you are certifying the device as intrinsically safe, you are
    > going to want to do your testing/analysis with the worst case
    > possible. That would be the battery with the highest s.c
    > current/lowest internal resistance.
    >
    > Someone is apt to ignore any vendor/part number specifications and
    > replace the battery with the first one that fits found in the parts
    > bin. This includes the possibility of replacing an alkaline battery
    > with a NiCad or NiMH battery, both of which may have lower internal
    > resistances if my memory serves me correctly.
    >


    I am sure that they will. Our customers return units (for repair or
    annual calibration) without the ground strap. Stating that we can't
    afford enough liability insurance to do otherwise, the ground strap is
    replaced and the customer charged for it. It is imposable to keep
    people from doing foolish things. The nameplate will have a list of
    approved batteries. The manual will probably have some words on why.
    We will remove batteries that are not on the list.

    Back to the short circuit current. From scraps of information, lithium
    batteries seam offer the highest currents. They also have a reputation
    for spectacular failure. Fortunately I did not have to talk very long
    to get them off of the wish list.

    Look for the test results towards the end.
    http://www.dtic.mil/ndia/2007power/...n6pres_RBYRNESJtServicesApr07presentation.pdf

    Robert
     
    Robert, Oct 19, 2008
    #13
  14. Robert

    Robert Guest

    JosephKK <> wrote in
    news:p:

    > On Wed, 15 Oct 2008 15:35:45 GMT, Robert <> wrote:
    >
    >>Hello everyone,
    >>
    >>A battery powered product is headed for “intrinsically safe”
    >>certification. The main test documented in prior certificates uses
    >>the open circuit voltage and short circuit current from the power
    >>source to see if an explosive mixture of gases can be ignited. The
    >>circuit capacitance is placed across the combination of a bench supply
    >>and a limiting resistor for the test.
    >>
    >>I am looking for information on the short circuit current for 9V and
    >>AA batteries. This varies by manufacturer, model, and from battery to
    >>battery. I would also like to hear if anyone has ever tested small
    >>batteries for short circuit current.
    >>
    >>Have a good day,
    >>Robert

    >
    > If you need an intrinsically safe level, please consider sealed
    > apparatus. Otherwise the limits are like 50 uA and 5 V at all times.
    > Moreover applications like explosimeters, are constrained to replacing
    > batteries in clear atmospheres.
    >
    >


    This is a rework of an existing product that is already approved
    intrinsically safe. Unfortunately, like many businesses, documentation
    and history from the prior approval was not maintained.

    The case is well sealed. Fortunately this redesign is just a new circuit
    board and replacing the 9V battery with two AAs.

    Robert
     
    Robert, Oct 20, 2008
    #14
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