Mystery component in NiCad battery pack
 

Hi

Rebuilding what I thought was a dead NiCad pack for a cordless phone.
The battery pack in question is a Sony BP-T18 - 3.6v, 600mAh. In series
connecting 2 of the batteries is an open component with these markings:

bel 2A
MO 125V

I can't i.d. it based on the markings. It kind of looks like a small 1
amp rectifier diode, as far as size and shape go, but there is no
polarity marking on it. I think it's some kind of (blown) fuse? I've
never seen this in a 3.6v phone battery pack.

If it is a fuse, why would they put one in a simple nicad battery pack
for a cordless phone? Is it safe to just bypass it? I do have a parts
source for micro fuses with leads. (Which look quite different from this
one, but would fit.)

If it isn't a fuse, what the heck is it?

Rick

Rick wrote:
If it is a fuse, why would they put one in a simple nicad battery pack
for a cordless phone?

One possible reason that springs to mind is to stop anything nasty
happening if the terminals on the pack are shorted.

Does the resistance change with temperature i.e. when cooled or heated slightly or does it just register as a short citcuit?

It could be a thermistor or a thermal fuse.

If it is a fuse, why would they put one in a simple nicad battery
pack
for a cordless phone?

You've never seen a guy put a nicad battery pack into his pocket along
with loose change and some keys, I take it :-). NiCads are very
capable of getting very hot when shorted out.

From your description as a cylindrical package it sounds like that may
be a Bel MQ or MS style package (page 1123 in current Digikey catalog.)

Tim.

Have you not heard of all the people having their faces burned by an
exploding cell phone battery?

I have seen several TV news reports which claim it it caused by using
replacement batteries made by someone other than the phone
manufacturer.

There was one report of a girl who had her hip pocket blown off her
jeans. (They only showed the jeans on TV).

Van

I started down this same road the other day. Actually, the nicad pack in
my phone wasn't dead - it was just real old and wouldn't hold a decent
charge any more. My local Circuit City wanted something like $19 for a
replacement pack. I considered that outrageous, and decided to
"restuff" it with three new nicad cells. As I was getting ready to
leave Circuit City, I noticed a cordless phone on sale - for $7! Not a
wonderful phone, but guess what was inside it? The EXACT SAME battery
pack that was selling for $19 on a bubble card on the other side of the
aisle.

Needless to say, I didn't pay $19 for the bubble card pack, and I didn't
rebuild the old one ...

Bill Jeffrey
=====================

Rick wrote:
Hi

Rebuilding what I thought was a dead NiCad pack for a cordless phone.
The battery pack in question is a Sony BP-T18 - 3.6v, 600mAh. In series
connecting 2 of the batteries is an open component with these markings:

bel 2A
MO 125V

I can't i.d. it based on the markings. It kind of looks like a small 1
amp rectifier diode, as far as size and shape go, but there is no
polarity marking on it. I think it's some kind of (blown) fuse? I've
never seen this in a 3.6v phone battery pack.

If it is a fuse, why would they put one in a simple nicad battery pack
for a cordless phone? Is it safe to just bypass it? I do have a parts
source for micro fuses with leads. (Which look quite different from this
one, but would fit.)

If it isn't a fuse, what the heck is it?

Rick

M.Joshi wrote:

Does the resistance change with temperature i.e. when cooled or heated
slightly or does it just register as a short citcuit?

No - it's open - not shorted.


It could be a thermistor or a thermal fuse.

Matthew Smith Wrote:
Rick wrote:-
If it is a fuse, why would they put one in a simple nicad battery
pack
for a cordless phone?-

One possible reason that springs to mind is to stop anything nasty
happening if the terminals on the pack are shorted.

--
M.Joshi

It is a miniature 2 amp fuse.

--

Jerry G.
======


"Rick" wrote in message ...
Hi

Rebuilding what I thought was a dead NiCad pack for a cordless phone.
The battery pack in question is a Sony BP-T18 - 3.6v, 600mAh. In series
connecting 2 of the batteries is an open component with these markings:

bel 2A
MO 125V

I can't i.d. it based on the markings. It kind of looks like a small 1
amp rectifier diode, as far as size and shape go, but there is no
polarity marking on it. I think it's some kind of (blown) fuse? I've
never seen this in a 3.6v phone battery pack.

If it is a fuse, why would they put one in a simple nicad battery pack
for a cordless phone? Is it safe to just bypass it? I do have a parts
source for micro fuses with leads. (Which look quite different from this
one, but would fit.)

If it isn't a fuse, what the heck is it?

Rick

"Rick" wrote in message ...
M.Joshi wrote:

Does the resistance change with temperature i.e. when cooled or heated
slightly or does it just register as a short citcuit?

No - it's open - not shorted.



Almost certainly a fuse, NiCd cells can provide a very high short circuit
current, fusing packs is always a good idea.

On Tue, 22 Feb 2005 04:20:54 -0500 Rick wrote:

Rebuilding what I thought was a dead NiCad pack for a cordless phone.
The battery pack in question is a Sony BP-T18 - 3.6v, 600mAh. In series
connecting 2 of the batteries is an open component with these markings:

It sounds like a thermal fuse. It opens if it gets too hot.

They are about 3/16" in dia and maybe 3/8" long, look like a metal
case axial lead capacitor with some color of plastic insulation around
where one lead exits.

Does this sound right?

Radio Shack carries a few temps of these.

-
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Jim Adney
Madison, WI 53711 USA
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