Mystery component in NiCad battery pack

[Rick]

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

 

[Matthew Smith]

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]

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

It could be a thermistor or a thermal fuse.

 

[M.Joshi]

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

It could be a thermistor or a thermal fuse.

 

[[email protected]]

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.

 

[[email protected]]

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

 

[Bill Jeffrey]

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]

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.

Yeah - I get it. It just seems like that would be a very hard thing to
short out, considering how the pack is put together. Like I said, FWIW,
this is the only cordless phone nicad pack I've ever seen it in. So
far...

be a Bel MQ or MS style package (page 1123 in current Digikey catalog.)

Tim.

Hi Tim

I don't have a DigiKey any more. But I take it then that it a fuse? If
it is, I can get a pico fuse with the same ratings elsewhere.

Thanks

Rick

 

[Rick]

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.

 

[Jerry G.]

It is a miniature 2 amp fuse.

--

Jerry G.
======


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

 

[James Sweet]

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.

 

[Jim Adney]

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.

-