Hot Batteries in TV Remote

[powrwrap]

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?

 

[Adrian C]

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.

 

[hr(bob) [email protected]]

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.

 

[Ronbo]

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.

 

[powrwrap]

On Dec 11, 11:29 am, powrwrap <[email protected]> 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]

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?

 

[Gareth Magennis]

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.

 

[Adrian C]

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.

 

[powrwrap]

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.

 

[webpa]

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.

 

[powrwrap]

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.