View Single Post
  #12   Report Post  
Posted to
webpa webpa is offline
external usenet poster
Posts: 52
Default Hot Batteries in TV Remote

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

- *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.