Hot Batteries in TV Remote

Discussion in 'Electronic Repair' started by powrwrap, Dec 11, 2008.

  1. powrwrap

    powrwrap Guest

    My son noticed that the battery area of our TV remote was quite hot. I
    immediately removed the batteries, both were almost too hot to hold
    onto. Sorry, I didn't check to see if the batteries were installed
    with the polarities correct. They had gotten so hot that the plastic
    surrounding the negative terminal that connects to the PCB was
    slightly melted and deformed.

    A new set of batteries did not cause the remote to function.

    I disassembled the remote and completely cleaned it. Scraped gunk out
    of the holes in the remote casing with a small jewelers screwdriver
    followed with a toothbrush and soapy water. Cleaned the flexible
    plastic sheet that functions as the button pad with soapy water and
    toothbrush. Completely dried everything with a hair dryer. Carefully
    pulled on spring for neg. terminal, stretching it so it will retain a
    battery, reassembled and put in fresh set of batteries. All is well.

    What caused the batteries to get hot?
     
    powrwrap, Dec 11, 2008
    #1
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  2. powrwrap

    Adrian C Guest

    powrwrap wrote:
    > My son noticed that the battery area of our TV remote was quite hot. I
    > immediately removed the batteries, both were almost too hot to hold
    > onto.


    > What caused the batteries to get hot?


    Dunno, probably an internal short from leaking somewhere, or perhaps
    some object was sitting on the remote a long time?. Looks like you may
    have cleared it now.

    Anyway - please make sure that the batteries you are using in this are
    NOT of the rechargeable type. If they are, that would explain the high
    temperatures and deformed terminal.

    --
    Adrian C
     
    Adrian C, Dec 11, 2008
    #2
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  3. powrwrap

    hr(bob) Guest

    On Dec 11, 11:29 am, powrwrap <> wrote:
    > My son noticed that the battery area of our TV remote was quite hot. I
    > immediately removed the batteries, both were almost too hot to hold
    > onto. Sorry, I didn't check to see if the batteries were installed
    > with the polarities correct. They had gotten so hot that the plastic
    > surrounding the negative terminal that connects to the PCB was
    > slightly melted and deformed.
    >
    > A new set of batteries did not cause the remote to function.
    >
    > I disassembled the remote and completely cleaned it. Scraped gunk out
    > of the holes in the remote casing with a small jewelers screwdriver
    > followed with a toothbrush and soapy water. Cleaned the flexible
    > plastic sheet that functions as the button pad with soapy water and
    > toothbrush. Completely dried everything with a hair dryer. Carefully
    > pulled on spring for neg. terminal, stretching it so it will retain a
    > battery, reassembled and put in fresh set of batteries. All is well.
    >
    > What caused the batteries to get hot?


    If the batteries were making poor contact with the negative spring,
    that in itself could have caused localized heating right at the spring.
     
    hr(bob) , Dec 11, 2008
    #3
  4. powrwrap

    Ronbo Guest

    powrwrap wrote:
    > My son noticed that the battery area of our TV remote was quite hot. I
    > immediately removed the batteries, both were almost too hot to hold
    > onto. Sorry, I didn't check to see if the batteries were installed
    > with the polarities correct. They had gotten so hot that the plastic
    > surrounding the negative terminal that connects to the PCB was
    > slightly melted and deformed.
    >
    > A new set of batteries did not cause the remote to function.
    >
    > I disassembled the remote and completely cleaned it. Scraped gunk out
    > of the holes in the remote casing with a small jewelers screwdriver
    > followed with a toothbrush and soapy water. Cleaned the flexible
    > plastic sheet that functions as the button pad with soapy water and
    > toothbrush. Completely dried everything with a hair dryer. Carefully
    > pulled on spring for neg. terminal, stretching it so it will retain a
    > battery, reassembled and put in fresh set of batteries. All is well.
    >
    > What caused the batteries to get hot?


    The resistance of the poor connections.
     
    Ronbo, Dec 11, 2008
    #4
  5. powrwrap

    powrwrap Guest

    On Dec 11, 1:17 pm, "hr(bob) " <>
    wrote:
    > On Dec 11, 11:29 am, powrwrap <> wrote:


    > If the batteries were making poor contact with the negative spring,
    > that in itself could have caused localized heating right at the spring.


    OK that's plausible. I'll stretch the springs out even more.
     
    powrwrap, Dec 11, 2008
    #5
  6. powrwrap

    powrwrap Guest

    > On Dec 11, 1:33 pm, Meat Plow <> wrote:
    >
    > >What caused the batteries to get hot?

    >
    > The battery Fairy?  
    >
    > Sorry I find this a bit hard to believe based upon my knowledge of
    > built in saftey by design and my three and a half decades in the
    > industry.


    Yeah, I've got nothing better to do than make up stories.

    Would you like me to post a photo of the melted plastic section that
    houses the negative terminal spring?
     
    powrwrap, Dec 11, 2008
    #6
  7. "hr(bob) " <> wrote in message
    news:...
    On Dec 11, 11:29 am, powrwrap <> wrote:
    > My son noticed that the battery area of our TV remote was quite hot. I
    > immediately removed the batteries, both were almost too hot to hold
    > onto. Sorry, I didn't check to see if the batteries were installed
    > with the polarities correct. They had gotten so hot that the plastic
    > surrounding the negative terminal that connects to the PCB was
    > slightly melted and deformed.
    >
    > A new set of batteries did not cause the remote to function.
    >
    > I disassembled the remote and completely cleaned it. Scraped gunk out
    > of the holes in the remote casing with a small jewelers screwdriver
    > followed with a toothbrush and soapy water. Cleaned the flexible
    > plastic sheet that functions as the button pad with soapy water and
    > toothbrush. Completely dried everything with a hair dryer. Carefully
    > pulled on spring for neg. terminal, stretching it so it will retain a
    > battery, reassembled and put in fresh set of batteries. All is well.
    >
    > What caused the batteries to get hot?


    If the batteries were making poor contact with the negative spring,
    that in itself could have caused localized heating right at the spring.





    How so? The maximum current draw of the remote can't be very much at all,
    so how can this max current through the dirty contact resistance cause so
    much heat as to melt the plastic? Am I missing something?

    If the remote is too hot to hold that can only be caused by pretty much
    shorting out the batteries or the batteries shorting out each other.


    Gareth.
     
    Gareth Magennis, Dec 11, 2008
    #7
  8. powrwrap

    Adrian C Guest

    Dave Platt wrote:
    Or, possibly, some conductive liquid (salty
    > broth?) was spilled onto/into the remote, and resulted in a near
    > short circuit.


    There was mention of a leaking battery. Perhaps the liquid shorted over
    the base of the LED driver transistor and drove Amps through the thing.

    --
    Adrian C
     
    Adrian C, Dec 12, 2008
    #8
  9. powrwrap

    powrwrap Guest

    On Dec 11, 3:46 pm, (Dave Platt) wrote:

    > The connection resistance would be an issue - it was probably the
    > local site-of-generation of the heat which started to melt the
    > plastic.  However, I think it's a secondary issue, and not the only
    > source of heat generation - the internal resistance of the batteries
    > would also have been a generator.
    >
    > The real question is, why was so much current being drawn from the
    > batteries (and released as heat)?  A remote control, when working
    > properly, is a relatively low-current device (a few tens of
    > milliamperes, I imagine) with a relatively low duty transmission duty
    > cycle, and it shouldn't be drawing more than an infinitesimal amount
    > of power from the batteries when there's no button being pushed.
    >
    > I think there might be several reasons why this overheating might have
    > occurred:
    >
    > -  Batteries inserted backwards, in a remote which has a reverse-biased
    >    across-the-battery diode at the input to its electronics.  The
    >    diode could act as an effective short-circuit across the batteries
    >    if they were inserted backwards.  [Using such a diode, and not
    >    having a fuse or a resettable thermal current limiter in series
    >    with the battery, would seem like a Really Bad Idea.]


    > -  Some bit of metal came loose inside the case (maybe a loose
    >    connector, maybe a stray bit of wire) and short-circuited the
    >    battery connections.  Or, possibly, some conductive liquid (salty
    >    broth?) was spilled onto/into the remote, and resulted in a near
    >    short circuit.


    > -  A cat sat on the remote, it started transmitting continuously, and
    >    (due to bad design or some sort of internal circuit fault) it drewso
    >    much current that it overheated.


    > I tend to lean towards the second possibility, myself.  


    No cat, and no evidence of anything spilled on the remote. I do know
    that the springs on the negative battery terminals had been compressed
    over the years and the batteries were not snug in the compartment.

    How about the battery was loosely set in the battery drawer AND the
    remote was wedged between the sofa cushions constantly pressing down
    on some buttons. It's been like that overnight. Then my son comes
    along, pulls the remote out from the cushions and notices it is hot.
    (?)

    I'll ask him if the remote was wedged in the sofa when he gets home
    from school.
     
    powrwrap, Dec 12, 2008
    #9
  10. powrwrap

    webpa Guest

    On Dec 12, 8:40 am, powrwrap <> wrote:
    > On Dec 11, 3:46 pm, (Dave Platt) wrote:
    >
    >
    >
    > > The connection resistance would be an issue - it was probably the
    > > local site-of-generation of the heat which started to melt the
    > > plastic.  However, I think it's a secondary issue, and not the only
    > > source of heat generation - the internal resistance of the batteries
    > > would also have been a generator.

    >
    > > The real question is, why was so much current being drawn from the
    > > batteries (and released as heat)?  A remote control, when working
    > > properly, is a relatively low-current device (a few tens of
    > > milliamperes, I imagine) with a relatively low duty transmission duty
    > > cycle, and it shouldn't be drawing more than an infinitesimal amount
    > > of power from the batteries when there's no button being pushed.

    >
    > > I think there might be several reasons why this overheating might have
    > > occurred:

    >
    > > -  Batteries inserted backwards, in a remote which has a reverse-biased
    > >    across-the-battery diode at the input to its electronics.  The
    > >    diode could act as an effective short-circuit across the batteries
    > >    if they were inserted backwards.  [Using such a diode, and not
    > >    having a fuse or a resettable thermal current limiter in series
    > >    with the battery, would seem like a Really Bad Idea.]
    > > -  Some bit of metal came loose inside the case (maybe a loose
    > >    connector, maybe a stray bit of wire) and short-circuited the
    > >    battery connections.  Or, possibly, some conductive liquid (salty
    > >    broth?) was spilled onto/into the remote, and resulted in a near
    > >    short circuit.
    > > -  A cat sat on the remote, it started transmitting continuously, and
    > >    (due to bad design or some sort of internal circuit fault) it drew so
    > >    much current that it overheated.
    > > I tend to lean towards the second possibility, myself.  

    >
    > No cat, and no evidence of anything spilled on the remote. I do know
    > that the springs on the negative battery terminals had been compressed
    > over the years and the batteries were not snug in the compartment.
    >
    > How about the battery was loosely set in the battery drawer AND the
    > remote was wedged between the sofa cushions constantly pressing down
    > on some buttons. It's been like that overnight. Then my son comes
    > along, pulls the remote out from the cushions and notices it is hot.
    > (?)
    >
    > I'll ask him if the remote was wedged in the sofa when he gets home
    > from school.


    Have had this sort of thing happen twice over the years...the cause
    was the same both times: Child who could not keep his fingers out of
    anything with moving parts; batteries removed and re-inserted more or
    less continuously for hours on end. Until one of the cells was
    inserted backwards. Remote survived in one case, did not survive in
    the other. This is not conjecture...child is now an adult and
    confessed in detail after returning from a deployment cruise.
     
    webpa, Dec 15, 2008
    #10
  11. powrwrap

    powrwrap Guest

    It happened again last night. I watched the 6 p.m. news, shut the TV
    off and put the remote on the end table. My entire family went out
    Christmas shopping. At about 8:30 my son picked up the remote to turn
    on the TV and it was hot. The batteries were extremely hot. The
    negative terminal was melted more than the original episode. Very
    strange.

    Obviously the thing is toast. Am now shopping for a new remote.
    Probably will get a universal.
     
    powrwrap, Dec 19, 2008
    #11
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