DaveC wrote:
Panasonic 2.4v screwdriver battery pack consists of 2x sub-C cells in
series. Pack has (+) and (-) terminals, and a 3rd terminal (charge
sense?).

This 3rd terminal connects the charge circuit to the pack's (-)
terminal through 2 diodes and 2 resistors, all in series. The diodes
are glass with a yellow band. When I hook it up to the charger, the
diodes each drop 0.535v.

What are these diodes? Germanium would drop 0.3v or less, and silicon
would drop more than this 0.5, no?

They could be silicon. What was the current? A 1N4148 drops about 0.5v at
around 150 micro-amps.

Farnell sell Schottky diodes with forward voltage drops ranging from 0.2 to
1.2V.

"Andrew Holme" wrote in message
...
DaveC wrote:
Panasonic 2.4v screwdriver battery pack consists of 2x sub-C cells
in
series. Pack has (+) and (-) terminals, and a 3rd terminal (charge
sense?).

This 3rd terminal connects the charge circuit to the pack's (-)
terminal through 2 diodes and 2 resistors, all in series. The
diodes
are glass with a yellow band. When I hook it up to the charger,
the
diodes each drop 0.535v.

What are these diodes? Germanium would drop 0.3v or less, and
silicon
would drop more than this 0.5, no?

They could be silicon. What was the current? A 1N4148 drops about
0.5v at
around 150 micro-amps.

Farnell sell Schottky diodes with forward voltage drops ranging from
0.2 to
1.2V.




Actually a silicon diode drops 600mV, prettywell consistently
irrespective of type.

Have you tried reverse supply through a resistor? They could be
zeners.

Either way they are part of the charge sense or charging circuit. If
the battery has three contacts, then you have +ve out, -ve out, and
charge probably common to -ve. The diodes ensure polarity, the
resistors control the charge current, simple as that.


--
Woody

harrogate2 at ntlworld dot com

"harrogate2" wrote in message
...

"Andrew Holme" wrote in message
...
DaveC wrote:
Panasonic 2.4v screwdriver battery pack consists of 2x sub-C cells
in
series. Pack has (+) and (-) terminals, and a 3rd terminal (charge
sense?).

This 3rd terminal connects the charge circuit to the pack's (-)
terminal through 2 diodes and 2 resistors, all in series. The
diodes
are glass with a yellow band. When I hook it up to the charger,
the
diodes each drop 0.535v.

What are these diodes? Germanium would drop 0.3v or less, and
silicon
would drop more than this 0.5, no?

They could be silicon. What was the current? A 1N4148 drops about
0.5v at
around 150 micro-amps.

Farnell sell Schottky diodes with forward voltage drops ranging from
0.2 to
1.2V.




Actually a silicon diode drops 600mV, prettywell consistently
irrespective of type.


According to the datasheet, the 1N4148 drops 1V at 10mA, which surprised me.

Have you tried reverse supply through a resistor? They could be
zeners.

Either way they are part of the charge sense or charging circuit. If
the battery has three contacts, then you have +ve out, -ve out, and
charge probably common to -ve. The diodes ensure polarity, the
resistors control the charge current, simple as that.


Diodes can be used as temperature sensors, and there's an outside chance
that they monitor the battery temperature. It's unlikely but worth bearing
in mind.

If they are 1N4148s and they are carrying the charge current it seems a bit
of corner-cutting by the manufacturer. 1N400x would have been a better
option IMO.

Dave

On Wed, 12 Jan 2005 20:46:42 +0000, harrogate2 wrote:


"Andrew Holme" wrote in message
...
DaveC wrote:
Panasonic 2.4v screwdriver battery pack consists of 2x sub-C cells
in
series. Pack has (+) and (-) terminals, and a 3rd terminal (charge
sense?).

This 3rd terminal connects the charge circuit to the pack's (-)
terminal through 2 diodes and 2 resistors, all in series. The
diodes
are glass with a yellow band. When I hook it up to the charger,
the
diodes each drop 0.535v.

What are these diodes? Germanium would drop 0.3v or less, and
silicon
would drop more than this 0.5, no?

They could be silicon. What was the current? A 1N4148 drops about
0.5v at
around 150 micro-amps.

Farnell sell Schottky diodes with forward voltage drops ranging from
0.2 to
1.2V.




Actually a silicon diode drops 600mV, prettywell consistently irrespective
of type.

No. The voltage drop of a diode is VERY dependant on the current flowing
through it, a 1N4001 diode can range in drop between ~0.3 and ~1.0
depending on the current flow. The 0.6 that is common is just a convinient
number to use. TTYL

On Wed, 12 Jan 2005 20:46:42 GMT, "harrogate2" wroth:



Actually a silicon diode drops 600mV, prettywell consistently
irrespective of type.


Actually, a silicon diode drops (in the forward direction) any value
from 0.0 volts to more than a volt depending on the current through it.

Take a look at some typical characteristic curves from the data sheets.

Jim

On Wed, 12 Jan 2005 20:46:42 GMT "harrogate2"
wrote:

Actually a silicon diode drops 600mV, prettywell consistently
irrespective of type.

It IS independent of type, but it is completely dependent on current
and temp. If you check the data sheets, it varies from nearly zero
(for nearly zero current) to about 1V (at the device's full rated
current.) For typical current values, however, .5-.75V is a good
estimate.

-
-----------------------------------------------
Jim Adney
Madison, WI 53711 USA
-----------------------------------------------

"DaveC" wrote in message
al.net...
Panasonic 2.4v screwdriver battery pack consists of 2x sub-C cells in
series.
Pack has (+) and (-) terminals, and a 3rd terminal (charge sense?).

This 3rd terminal connects the charge circuit to the pack's (-) terminal
through 2 diodes and 2 resistors, all in series. The diodes are glass with
a
yellow band. When I hook it up to the charger, the diodes each drop
0.535v.

What are these diodes? Germanium would drop 0.3v or less, and silicon
would
drop more than this 0.5, no?

I want to make more battery packs for this screwdriver and need to
identify
these diodes.


Most likely a 1N4148, a silicon diode. They are as common as muck and very
cheap.
http://www.semiconductors.philips.co...8_1N4448_5.pdf

You won't find germanium diodes in a battery pack, they're still used but
only for specialised purposes.

Dave

On Wed, 12 Jan 2005 11:21:08 -0800, DaveC wrote:

Panasonic 2.4v screwdriver battery pack consists of 2x sub-C cells in
series. Pack has (+) and (-) terminals, and a 3rd terminal (charge
sense?).

This 3rd terminal connects the charge circuit to the pack's (-) terminal
through 2 diodes and 2 resistors, all in series. The diodes are glass with
a yellow band. When I hook it up to the charger, the diodes each drop
0.535v.

What are these diodes? Germanium would drop 0.3v or less, and silicon
would drop more than this 0.5, no?

I want to make more battery packs for this screwdriver and need to
identify these diodes.

While they could be standard pn junction silicon diodes, my guess would be
they are schottky. TTYL

repatch wrote:
On Wed, 12 Jan 2005 11:21:08 -0800, DaveC wrote:


Panasonic 2.4v screwdriver battery pack consists of 2x sub-C cells in
series. Pack has (+) and (-) terminals, and a 3rd terminal (charge
sense?).

This 3rd terminal connects the charge circuit to the pack's (-) terminal
through 2 diodes and 2 resistors, all in series. The diodes are glass with
a yellow band. When I hook it up to the charger, the diodes each drop
0.535v.

What are these diodes? Germanium would drop 0.3v or less, and silicon
would drop more than this 0.5, no?

I want to make more battery packs for this screwdriver and need to
identify these diodes.


While they could be standard pn junction silicon diodes, my guess would be
they are schottky. TTYL


Why?

--
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"DaveC" wrote in message
al.net...
Panasonic 2.4v screwdriver battery pack consists of 2x sub-C cells in
series.
Pack has (+) and (-) terminals, and a 3rd terminal (charge sense?).

This 3rd terminal connects the charge circuit to the pack's (-) terminal
through 2 diodes and 2 resistors, all in series. The diodes are glass with
a
yellow band. When I hook it up to the charger, the diodes each drop
0.535v.

What are these diodes? Germanium would drop 0.3v or less, and silicon
would
drop more than this 0.5, no?

I want to make more battery packs for this screwdriver and need to
identify
these diodes.

Thanks,
--
Please, no "Go Google this" replies. I wouldn't
ask a question here if I hadn't done that already.

DaveC

This is an invalid return address
Please reply in the news group

Does the third terminal connect to the junction of the two nicads? You can
check that by seeeing if it is at 1/2 voltage. Do the diodes make any
connection to that?

Tam

As others have pointed out, they could well be silicon diodes, but are they
temperature sensors? I'd expect to find temperature sensors in a battery
pack.

"DaveC" wrote in message
al.net...
Panasonic 2.4v screwdriver battery pack consists of 2x sub-C cells in
series.
Pack has (+) and (-) terminals, and a 3rd terminal (charge sense?).

This 3rd terminal connects the charge circuit to the pack's (-) terminal
through 2 diodes and 2 resistors, all in series. The diodes are glass with
a
yellow band. When I hook it up to the charger, the diodes each drop
0.535v.

What are these diodes? Germanium would drop 0.3v or less, and silicon
would
drop more than this 0.5, no?

I want to make more battery packs for this screwdriver and need to
identify
these diodes.

Thanks,
--
Please, no "Go Google this" replies. I wouldn't
ask a question here if I hadn't done that already.

DaveC

This is an invalid return address
Please reply in the news group

"mc" wrote in message
...
As others have pointed out, they could well be silicon diodes, but are
they
temperature sensors? I'd expect to find temperature sensors in a battery
pack.


They could be both. Diodes can be used to sense temperature.

Dave

On Wed, 12 Jan 2005 23:41:14 +0000, Dave D wrote:


"mc" wrote in message
...
As others have pointed out, they could well be silicon diodes, but are
they
temperature sensors? I'd expect to find temperature sensors in a battery
pack.


They could be both. Diodes can be used to sense temperature.

If one is up against one cell, and the other is up against the other cell,
physically touching, then it's almost a sure thing that they're temp.
sensors.

Cheers!
Rich

"DaveC" schreef in bericht
al.net...
Panasonic 2.4v screwdriver battery pack consists of 2x sub-C cells in
series.
Pack has (+) and (-) terminals, and a 3rd terminal (charge sense?).

This 3rd terminal connects the charge circuit to the pack's (-) terminal
through 2 diodes and 2 resistors, all in series. The diodes are glass with
a
yellow band. When I hook it up to the charger, the diodes each drop
0.535v.

What are these diodes? Germanium would drop 0.3v or less, and silicon
would
drop more than this 0.5, no?

I want to make more battery packs for this screwdriver and need to
identify
these diodes.

Thanks,
--
Please, no "Go Google this" replies. I wouldn't
ask a question here if I hadn't done that already.

DaveC

This is an invalid return address
Please reply in the news group


You did neither tell the resistor values nor the voltage measured across
them. Should be of some help. Can only guess these are old 1N914 or similar.
Most likely used for temperature sensing. The temperature itself is not very
important. It is the changing of it (dT/dt) that is used to decide whether
the batteries are fully charged.

petrus bitbyter

Just to be different, Could the diodes and resistors be used to trickle
charge after the batteries are fully charged.
The charger output switches from the ( - ) neg of the battery to the
resistor diode string connected to ( - ) neg,
and allows for long times on the charger without cooking the batteries.
Mike

"DaveC" wrote in message
al.net...
Panasonic 2.4v screwdriver battery pack consists of 2x sub-C cells in
series.
Pack has (+) and (-) terminals, and a 3rd terminal (charge sense?).

This 3rd terminal connects the charge circuit to the pack's (-) terminal
through 2 diodes and 2 resistors, all in series. The diodes are glass with
a
yellow band. When I hook it up to the charger, the diodes each drop
0.535v.

What are these diodes? Germanium would drop 0.3v or less, and silicon
would
drop more than this 0.5, no?

I want to make more battery packs for this screwdriver and need to
identify
these diodes.

Thanks,
--
Please, no "Go Google this" replies. I wouldn't
ask a question here if I hadn't done that already.

DaveC

This is an invalid return address
Please reply in the news group

amdx wrote:

Just to be different, Could the diodes and resistors be used to trickle
charge after the batteries are fully charged.
The charger output switches from the ( - ) neg of the battery to the
resistor diode string connected to ( - ) neg,
and allows for long times on the charger without cooking the batteries.
Mike

Yet one more "different"... how about if the voltage drop
across the resistor is compared to the breakdown voltage
of the diode to determine the state of charge?

Ken

"amdx" wrote in message
...
| Just to be different, Could the diodes and resistors be used to trickle
| charge after the batteries are fully charged.
| The charger output switches from the ( - ) neg of the battery to the
| resistor diode string connected to ( - ) neg,
| and allows for long times on the charger without cooking the batteries.
| Mike

No point. Why put them in the battery? Makes more sense for either

1) Sensing

or

2) Calibrated compensation.

N

On Thu, 13 Jan 2005 04:51:15 GMT, "NSM" wrote:


"amdx" wrote in message
...
| Just to be different, Could the diodes and resistors be used to trickle
| charge after the batteries are fully charged.
| The charger output switches from the ( - ) neg of the battery to the
| resistor diode string connected to ( - ) neg,
| and allows for long times on the charger without cooking the batteries.
| Mike

No point. Why put them in the battery? Makes more sense for either

1) Sensing

or

2) Calibrated compensation.

N

Or it's there as a fuse.(thermally sensitive it blows when the battery
starts to overheat. Helps to prevent a battery exploding.)

Almost certain to be used as a temperature sensor (relying
on the "Diode Equation"), the abrupt rise in temperature
indicating when charging is complete.

"DaveC" wrote in message
al.net...
Panasonic 2.4v screwdriver battery pack consists of 2x sub-C cells in
series.
Pack has (+) and (-) terminals, and a 3rd terminal (charge sense?).

This 3rd terminal connects the charge circuit to the pack's (-) terminal
through 2 diodes and 2 resistors, all in series. The diodes are glass with
a
yellow band. When I hook it up to the charger, the diodes each drop
0.535v.

What are these diodes? Germanium would drop 0.3v or less, and silicon
would
drop more than this 0.5, no?

I want to make more battery packs for this screwdriver and need to
identify
these diodes.

Thanks,
--
Please, no "Go Google this" replies. I wouldn't
ask a question here if I hadn't done that already.

DaveC

This is an invalid return address
Please reply in the news group

These diodes are possibly needed to rectify the ac provided by the charging
transformer, so that the batteries recveive dc.Check with your multimeter if
the terminals of the charger supply ac.Usually the diodes are silicone, as
germanium is more expensive.Do you have a retailer of electronic gear in
vicinity that has experience in this kind of parts?The one I buy everything
can identify almost anything just with one look.

--
Tzortzakakis Dimitri?s
major in electrical engineering, freelance electrician
FH von Iraklion-Kreta, freiberuflicher Elektriker
dimtzort AT otenet DOT gr
? "DaveC" ?????? ??? ??????
al.net...
Panasonic 2.4v screwdriver battery pack consists of 2x sub-C cells in
series.
Pack has (+) and (-) terminals, and a 3rd terminal (charge sense?).

This 3rd terminal connects the charge circuit to the pack's (-) terminal
through 2 diodes and 2 resistors, all in series. The diodes are glass with
a
yellow band. When I hook it up to the charger, the diodes each drop
0.535v.

What are these diodes? Germanium would drop 0.3v or less, and silicon
would
drop more than this 0.5, no?

I want to make more battery packs for this screwdriver and need to
identify
these diodes.

Thanks,
--
Please, no "Go Google this" replies. I wouldn't
ask a question here if I hadn't done that already.

DaveC

This is an invalid return address
Please reply in the news group

DaveC wrote:
Panasonic 2.4v screwdriver battery pack consists of 2x sub-C cells in series.
Pack has (+) and (-) terminals, and a 3rd terminal (charge sense?).

This 3rd terminal connects the charge circuit to the pack's (-) terminal
through 2 diodes and 2 resistors, all in series. The diodes are glass with a
yellow band. When I hook it up to the charger, the diodes each drop 0.535v.

What are these diodes? Germanium would drop 0.3v or less, and silicon would
drop more than this 0.5, no?

I want to make more battery packs for this screwdriver and need to identify
these diodes.

Thanks,

This has been another of those amusing threads.
You've gotten a zillion "answers" each of which could be paraphrased,
1)Stick your finger in the air, or your favorite orifice.
2)Make a GROSS, UNSUBSTANTIATED, SPECULATION based on NO, NONE, NOT ANY
information.

I read the thread again. I couldn't even find mention of the polarity
of the diodes in the circuit. Heck, one of us might even have relevant
information if only we knew the Panasonic model number.

You need to take apart the CHARGER and reverse engineer that.
If you published the schematic of the battery and charger, you MIGHT,
maybe, get a useful bit of information buried in the inevitable noise.
Then your problem would be reduced to deciding which of the conflicting
opinions to choose.

IF the charge termination is indeed based on temperature, and IF the
unknown elements are involved in temperature sensing, you need to
GET IT RIGHT. Did I mention IF???

Nah, who am I kidding. I'm certain the diodes are not diodes at all.
They're put there just to add to confusion in internet newsgroups.
Leave them out. Bummer, I think I got something on my finger... ;-)
mike

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"mike" wrote in message
...

| Nah, who am I kidding. I'm certain the diodes are not diodes at all.
| They're put there just to add to confusion in internet newsgroups.
| Leave them out. Bummer, I think I got something on my finger... ;-)

Actually, you're right. They're extra parts from the flying saucer used by
Kang and Kodos. They were going to build a rectal probe for Homer J, but, as
explained in "Treehouse of Horror VII" (1996) - The Halloween episode, they
decided against it. "I suppose you want to probe me," says Homer on board
the flying saucer and dropping his pants. "Well, you might as well get it
over with."

Kang replies, raising a tentacle, and shuddering: "Stop! We have reached the
limit of what rectal probing can teach us!"

I suspect we have reached the limit on what speculation on this battery can
teach us!

GW

(Always laugh at that one)

DaveC wrote:
Panasonic 2.4v screwdriver battery pack consists of 2x sub-C cells in series.
Pack has (+) and (-) terminals, and a 3rd terminal (charge sense?).

This 3rd terminal connects the charge circuit to the pack's (-) terminal
through 2 diodes and 2 resistors, all in series. The diodes are glass with a
yellow band. When I hook it up to the charger, the diodes each drop 0.535v.

What are these diodes? Germanium would drop 0.3v or less, and silicon would
drop more than this 0.5, no?

I want to make more battery packs for this screwdriver and need to identify
these diodes.

Thanks,

This is almost certainly a diode temperature sensor operating in
switched mode. In this mode, temperature is sensed based upon the diode
voltage differential at two separate currents: delta Vd= KT/q x Ln(
I1/I2), and this also explains why your readings are so low- the meter
is averaging- and the sensing may be operating in burst mode. The
resistors may serve any number of purposes- cheap current limiting or
simply to raise the input voltage level. Two diodes will double the
differential- but two resistors?- don't know.

Various manufactures may use their own particular designs to match up to
whatever they want in correspondence to their chosen designs.

Sometimes they use a diode coming from the battery pack to give a one way
isolation to the battery pack for their load testing circuit in their
charger. This blocks the load test circuit from feeding back in to the
battery pack. They sometimes use a resistor, or combination of resistors
with the diode for current limitation of some type, depending again, on what
they specifically want to do accomplish in their design.

Sometimes, they may also use a diode that is thermo sensitive, thus being
able to also determine if the temperature of the battery pack is going too
high. In this case the diode can be serving for several purposes.

If you are replacing this diode you will have to be sure of its
specifications before simply using any diode off the shelf. There may be
some safety and performance issues here. This is why I prefer to go out and
get the original battery packs for my equipment rather than jeopardizing
safety and performance for a few dollars saved.

--

Jerry G.
=====

"DaveC" wrote in message
al.net...
Panasonic 2.4v screwdriver battery pack consists of 2x sub-C cells in
series.
Pack has (+) and (-) terminals, and a 3rd terminal (charge sense?).

This 3rd terminal connects the charge circuit to the pack's (-) terminal
through 2 diodes and 2 resistors, all in series. The diodes are glass with a
yellow band. When I hook it up to the charger, the diodes each drop 0.535v.

What are these diodes? Germanium would drop 0.3v or less, and silicon would
drop more than this 0.5, no?

I want to make more battery packs for this screwdriver and need to identify
these diodes.

Thanks,
--
Please, no "Go Google this" replies. I wouldn't
ask a question here if I hadn't done that already.

DaveC

This is an invalid return address
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