NiCad Battery Charger repair

[[email protected]]

Have an OEM battery charger for mid-1980's equipment that does not
appear to be operating correctly. It has been longer than that since
my high school Physics' classes and I have exhausted my personal
"knowledge base" as to trying to diagnose and correct this "problem."

Any suggestions as to how to proceed will be appreciated.

Background:

The battery charger is marked as Input AC 120V, 50/60Hz, 5W
and Output of DC 10.43V 180 mA.

The Red LED for "operating" is not illuminating and the 3A fuse for
the equipment is blown.

Checked the battery charger secondary output at the connector and it
is reading 15.34 VDC with no load.

Main's current was 121.4 VAC

Opened the battery charger case. Transformer is marked as "206082" and
label logo appears to read as "SDB."

Secondary output side has three post. I will refer to them as L, C,
and R.

Voltage at L and C or at C and R is 13.74 VAC.

C feeds the lead to the equipment connector jack, the negative pole.

L and R each go to their individual diodes (can not read the values)
and then connect together. The voltage at either L or R to C, after
being rectified is 15.39 VDC.

The combined L & R then connects the lead to a 68 ohm resistor (which
feeds one side of the Red LED) and also into what I assume to be a
Ceramic Tubular Capacitor (light bluish colored, "dog-boned" shaped
with end leads and color banded Gold/blank/Gold/Gold/White(or
silver?))

Voltage across the two leads for the LED reads 0.000VDC.

The output lead of the "capacitor"? then feeds both the other lead of
the Red LED and continues as the Positive pole of the equipment
connector jack.

Questions:

1) Is the 15.37 VDC "no load" output at the connector representative
of a battery charger malfunction?

2) Is this a reason that the LED is not illuminating?

3) The OEM feels that this "simple" battery charger is worth US
$120.00. Any suggestions?


Again, thanks for any suggestions.

 

[Homer J Simpson]

Questions:

1) Is the 15.37 VDC "no load" output at the connector representative
of a battery charger malfunction?
No.

2) Is this a reason that the LED is not illuminating?

Probably not.

3) The OEM feels that this "simple" battery charger is worth US
$120.00. Any suggestions?

Repair the one you have.

 

[Jim Yanik]

[email protected] wrote in

Have an OEM battery charger for mid-1980's equipment that does not
appear to be operating correctly. It has been longer than that since
my high school Physics' classes and I have exhausted my personal
"knowledge base" as to trying to diagnose and correct this "problem."

Any suggestions as to how to proceed will be appreciated.

Background:

The battery charger is marked as Input AC 120V, 50/60Hz, 5W
and Output of DC 10.43V 180 mA.

The Red LED for "operating" is not illuminating and the 3A fuse for
the equipment is blown.

Checked the battery charger secondary output at the connector and it
is reading 15.34 VDC with no load.

Main's current was 121.4 VAC

Opened the battery charger case. Transformer is marked as "206082" and
label logo appears to read as "SDB."

Secondary output side has three post. I will refer to them as L, C,
and R.

Voltage at L and C or at C and R is 13.74 VAC.

C feeds the lead to the equipment connector jack, the negative pole.

L and R each go to their individual diodes (can not read the values)
and then connect together. The voltage at either L or R to C, after
being rectified is 15.39 VDC.

The combined L & R then connects the lead to a 68 ohm resistor (which
feeds one side of the Red LED) and also into what I assume to be a
Ceramic Tubular Capacitor (light bluish colored, "dog-boned" shaped
with end leads and color banded Gold/blank/Gold/Gold/White(or
silver?))

Voltage across the two leads for the LED reads 0.000VDC.

The output lead of the "capacitor"? then feeds both the other lead of
the Red LED and continues as the Positive pole of the equipment
connector jack.

Questions:

1) Is the 15.37 VDC "no load" output at the connector representative
of a battery charger malfunction?

2) Is this a reason that the LED is not illuminating?

3) The OEM feels that this "simple" battery charger is worth US
$120.00. Any suggestions?


Again, thanks for any suggestions.

It MIGHT help if you identified WHAT the "mid-1980's equipment"
IS;make,model,serial number.
Somebody here may have a manual or link to one.

 

[[email protected]]

[email protected] wrote in
---- clipped -----

It MIGHT help if you identified WHAT the "mid-1980's equipment"
IS;make,model,serial number.
Somebody here may have a manual or link to one.

--
Jim Yanik
jyanik
at
kua.net- Hide quoted text -

Hello Jim and thanks for the input. I was afraid that I had already
given too much information!

The equipment is a Topcon GTS-2B Geodetic Total Station, used for land
surveying. Most of the device is mechanical or optical/mechanical, but
the distance measuring function uses an 8.4 volt battery pack.

The battery charger is a Topcon Battery Charger BC-10B, which is used
for standard rate charging. When using the standard battery pack, the
BT-5Q (DC 8.4V output and 1.2AH capacity) the recommended charge time
is 8 hours.

Again, any ideas or suggestions will be appreciated.

 

[mike]

Have an OEM battery charger for mid-1980's equipment that does not
appear to be operating correctly. It has been longer than that since
my high school Physics' classes and I have exhausted my personal
"knowledge base" as to trying to diagnose and correct this "problem."

Any suggestions as to how to proceed will be appreciated.

What's the history?
Did it work yesterday and not today?
Did you pull it out of a dumpster?
If the latter, idle NiCd batteries go shorted and burn up stuff
when you turn on the charger.

A significant clue is that the fuse is blown, but you gloss
over that fact and don't describe where in the circuit it is.
It ain't likely to work with a blown fuse.
The problem is likely downstream of the fuse.

If you've got 15V on one side of the resistor and nothing
on the other you've got no current, which is consistent with a
blown fuse. Also consistent with open resistor or dogbone.

It's likely that the led illuminates only when there's sufficient
current to generate some volts across the dogbone.

Start with the blown fuse. Check for shorted batteries.
mike

 

[[email protected]]

Have an OEM battery charger for mid-1980's equipment that does not
appear to be operating correctly. It has been longer than that since
my high school Physics' classes and I have exhausted my personal
"knowledge base" as to trying to diagnose and correct this "problem."

Any suggestions as to how to proceed will be appreciated.

Background:

The battery charger is marked as Input AC 120V, 50/60Hz, 5W
and Output of DC 10.43V 180 mA.

The Red LED for "operating" is not illuminating and the 3A fuse for
the equipment is blown.

Checked the battery charger secondary output at the connector and it
is reading 15.34 VDC with no load.

Main's current was 121.4 VAC

Opened the battery charger case. Transformer is marked as "206082" and
label logo appears to read as "SDB."

Secondary output side has three post. I will refer to them as L, C,
and R.

Voltage at L and C or at C and R is 13.74 VAC.

C feeds the lead to the equipment connector jack, the negative pole.

L and R each go to their individual diodes (can not read the values)
and then connect together. The voltage at either L or R to C, after
being rectified is 15.39 VDC.

The combined L & R then connects the lead to a 68 ohm resistor (which
feeds one side of the Red LED) and also into what I assume to be a
Ceramic Tubular Capacitor (light bluish colored, "dog-boned" shaped
with end leads and color banded Gold/blank/Gold/Gold/White(or
silver?))

Voltage across the two leads for the LED reads 0.000VDC.

The output lead of the "capacitor"? then feeds both the other lead of
the Red LED and continues as the Positive pole of the equipment
connector jack.

Questions:

1) Is the 15.37 VDC "no load" output at the connector representative
of a battery charger malfunction?

2) Is this a reason that the LED is not illuminating?

3) The OEM feels that this "simple" battery charger is worth US
$120.00. Any suggestions?

Again, thanks for any suggestions.

---------------------
the LED should lite loaded or not
u mentioned no load output
what is the load u r putting on it?
is it a switching power supply 100-260Vac 50~60Hz or a linear PS
if bottom regulation voltage can be seen to ring when u lower ac
input on your scope then it is linear

 

[[email protected]]

Mike. Thanks for the questions. Let me expound on the situation so
that you and others may have more to ruminate on as to my battery
charger situation.

What's the history?

Battery charger (Topcon BC-10B) was properly charging the battery pack
on a GTS-2B "Total Station" (used for surveying). I had miswired the
connector to another port on the GTS-2B. Noticed a problem when saw
that the Red LED "charging" light was out. Checked battery charger's
output at the plug - saw more than 15 VDC. Then also noticed the blown
fuse on the GTS-2B.

Since the voltage read at the connector (15.39 VDC) was well above the
BC-10B's stated output of 10.43VDC and the battery pack is made up of
seven ni-cad cells (8.4 VDC) I was concerned that the BC-10B battery
charger was way out of tolerance.

As this is a simple, plug in the wall battery charger, I started
looking for a replacement. Topcon wants $120 for theirs. At that point
it was worth opening up to try to find the problem.

Did you pull it out of a dumpster?
If the latter, idle NiCd batteries go shorted and burn up stuff
when you turn on the charger.

No dumpster diving on this one. The battery pack was properly
functioning and the problem occured only after I miswired the hook-up
connectors while starting to recharge the battery pack.

A significant clue is that the fuse is blown, but you gloss
over that fact and don't describe where in the circuit it is.
It ain't likely to work with a blown fuse.
The problem is likely downstream of the fuse.

The fuse is on the GTS-2B equipment (actually associated with the
battery pack and it even has an On/Off switch that controls both
output (into the GTS-2B from the battery pack for distance measuring
operations) and input (for charging the battery pack - the switch must
be On for charging operations.)

I have +/- 15.4VDC (depending on the line current, it was 15.39 with
the line current at 121.4 VAC and directly proportional increase as
the line current changed) coming out of the battery charger, which I
initially measured at the charger's plug. Now that I have taken the
battery charger module apart, I measure a similar voltage at any point
after the current is rectified (the diodes are immediately after the
secondary side of the transformer.)

If you've got 15V on one side of the resistor and nothing
on the other you've got no current, which is consistent with a
blown fuse. Also consistent with open resistor or dogbone.

Have +/- 15.4vdc on both sides of the resistor when tapping to the
secondary side's center output post (supplies the negative for the
output plug).

The mention as to the 0.000 VDC was when I check the voltage of the
two legs going into the Red LCD.

One leg of the LED terminates into the output side of the 68 ohm
resistor.

On the output side of the "dog-bone" is a Tee where one leg runs to
the output plug as the Positive terminal and the other leg from this
Tee becomes the "other" leg into the Red LCD.

I do read +/- 68 ohms across the resistor as it sits, still wired into
the charger, but the charger's output jack is not hooked up to the
battery pack (and stating the obvious, not plugged into the line
current!)

Believe the "dog-bone" is a capacitor, but was not 100% certain. Is
what I described as a "dog-bone" a Ceramic Tubular Capacitor, and if
so, what capacity with the White(Silver?) / Gold / Gold / Gold
banding?

The "dog-bone" is still hooked up. Everything is still as it was as I
have only opened the battery charger case without breaking any
connections, up to this point.

It's likely that the led illuminates only when there's sufficient
current to generate some volts across the dogbone.

The "dog-bone" has +/- 15.4VDC on both sides. Do not have an easy way
to measure the current at this time. Possibly, I could hook up a small
automotive lamp to the plug to see if there is current.

Start with the blown fuse. Check for shorted batteries.

To review, the blown fuse and the batteries (which still have minimal
charge) are on the GTS-2B equipment. Replaced the fuse and the GTS-2B
equipment still works.

It is only because I no longer have an illuminated Red LED and my
checking of the output voltage (and my belief that this is way to
high) that I believe that I have a problem.

Do you think that I do have a problem (of course, I mean with the
battery charger!) and if so, any ideas of how to correct it/them?

Again, thanks for your input and attempts to help me.

 

[Dave Plowman (News)]

Battery charger (Topcon BC-10B) was properly charging the battery pack
on a GTS-2B "Total Station" (used for surveying). I had miswired the
connector to another port on the GTS-2B. Noticed a problem when saw
that the Red LED "charging" light was out. Checked battery charger's
output at the plug - saw more than 15 VDC. Then also noticed the blown
fuse on the GTS-2B.

If you managed to introduce a charged battery the wrong way round to the
charger that might account for a blown LED - they are polarity sensitive.

Since the voltage read at the connector (15.39 VDC) was well above the
BC-10B's stated output of 10.43VDC and the battery pack is made up of
seven ni-cad cells (8.4 VDC) I was concerned that the BC-10B battery
charger was way out of tolerance.

Voltage doesn't matter when charging Ni-Cads - within a wide range,
provided it is higher than the nominal pack voltage. It's the current
through the pack which is important and in this case (in the main) is set
by the series resistor.

As this is a simple, plug in the wall battery charger, I started
looking for a replacement. Topcon wants $120 for theirs. At that point
it was worth opening up to try to find the problem.

It has so few components it should be simple to test them all with a DVM -
and to see if it is actually producing charging current. The LED can be
checked by simple substitution - they are very cheap. Check also its
series resistor.

 

[Bill Jeffrey]

This is an extremely simple charger. Nicad chargers usually have a bit
more complexity. However, drawing up the circuit as you have described
it, I find:
1. The transformer is center tapped. C is the center tap, L and R are
the two ends. Given your choice of labels, I think you know this. The
two diodes provide full-wave rectification.
2. In this configuration, the voltage that you read beyond the diodes is
pretty meaningless, since your meter will read the peaks of the
rectified half-waves, not the average or the DC component.
3. The "capacitor" probably isn't a capacitor, since it is in series
with the battery being charged. I am assuming it is a low-value
resistor, which provides operating voltage for the LED.
4. You should read the color code from the other end - that is,
gold-gold-white-blank-gold. But regardless of whether it is cap or
resistor, that color code doesn't make sense. I am betting that it is
white-brown-gold, which would make it 9.1 ohms. If the entire battery
current (180 mA) passed through it, it would drop 1.6 volts, which is
not out of line for a LED. Its real purpose is to share some of the
charge current with the LED, so the LED doesn't get overdriven.
5. The LED is not expected to light unless a battery is being charged.
That is, if you simply plug the charger into the wall and set it on your
desk with no battery inserted, the LED won't light. However, if you put
something like a 47-ohm resistor across the charger terminals for a
moment, the LED should light. Is this what you observe?
6. Hooking up a battery backward will NOT damage the LED due to reverse
conduction. The rectifier diodes will prevent current from flowing.
7. Having said that, if you a) short the charger output, or b) insert a
battery backward and plug in the charger, it might damage either the LED
or the 9.1 ohm resistor or both, due to overcurrent. Assuming that the
LED does not light in step 5 above, I'm betting that the 9.1 ohm
resistor overheated (which would account for the difficulty in reading
the true colors of the bands) and failed open, at which point the LED
failed from overcurrent.

Hope this helps. To answer your question "Is it worth spending $100+ to
replace this thing", the answer is no. You can replace the LED and the
resistor for less than a buck each (Radio Shack). Before you do so, I
would recommened using the ohmmeter part of your VOM or DVM to confirm
that a) the rectifier diodes are still diodes, b) the 68 ohm resistore
is good, c) the LED looks like a diode (or doesn't), and d) the 9.1 ohm
resistor is way out of whack (or isn't).

Bil Jeffrey
-----------------------------------

 

[Jim Yanik]

[email protected] wrote in

Hello Jim and thanks for the input. I was afraid that I had already
given too much information!

The equipment is a Topcon GTS-2B Geodetic Total Station, used for land
surveying. Most of the device is mechanical or optical/mechanical, but
the distance measuring function uses an 8.4 volt battery pack.

The battery charger is a Topcon Battery Charger BC-10B, which is used
for standard rate charging. When using the standard battery pack, the
BT-5Q (DC 8.4V output and 1.2AH capacity) the recommended charge time
is 8 hours.

that's a slow charge rate;must be a trickle charger.

Again, any ideas or suggestions will be appreciated.

NiCds charge at ~1.5x the pack voltage,usual slow charge rate is 1/10
C,takes several hours,but IMO,NiCds do better with fast charges,1 hr or
less.("C"= AH rating,IOW,Capacity.)
But for fast charge,you need a temp sensor or a smart IC to monitor cell
voltage.

With most trickle chargers,you need to use a timer so you don't OVERcharge
the cells,shortening their life.


1.2AH would be AA-size cells.IIRC,AA NiCds are around 1200mAH.

AA NiMH cells go even higher,around 2200mAH.

since your charger outputs a much higher voltage,I suspect the regulating
circuit has shorted or failed.

 

[cmdrdata]

[email protected] wrote in

Its amazing the various replies you got on this problem. Reading your
description of the circuit, it sounded like a simple fullwave bridge
rectifier circuit converting transformer secondary AC voltage via two
discrete diodes with the no "regulation" whatsoever and a light load /
power indicator of LED with current limiting resistor. So, if I were
you, instead of being gouged by the vendor wanting 120 dollars, find
a similar DC wall power supply with output spec near 10-11 VDC
( similar current rating capability) and adapt the power plugs (cut
off and rewire the old to new one), and your problem is solved.

Nicads, like someone posted is pretty tolerant to voltage levels, and
like to be charged at 1/10th the AH capacity or if you're willing to
tolerate it, at even lower charge rate. As far as the LED not
lighting up, I would check the LED and the limiting resistor. One of
them is probably open circuit. Also, if you hook up 100 ohm load on
the output leads, my guess is that the open voltage measurement you
got will drop down a few volts closer ot the label voltage rating you
mentioned. If the voltage with the load on drops real low, then
perhaps you have a shorted winding in the transformer, thus unable to
even proved the 100-150 mA charging current.

The fuse thing was a misleading issue, since you miswired it when it
happened.

 

[Gary Tait]

1.2AH would be AA-size cells.IIRC,AA NiCds are around 1200mAH.

Likely Sub-C cells, considering the date. AA cells would be around 600 mAH.

$120 for a replacement charger doesn't seem out of line considering the age
and nature of the equipment.

 

[mike]

Its amazing the various replies you got on this problem. Reading your
description of the circuit, it sounded like a simple fullwave bridge
rectifier circuit converting transformer secondary AC voltage via two
discrete diodes with the no "regulation" whatsoever and a light load /
power indicator of LED with current limiting resistor. So, if I were
you, instead of being gouged by the vendor wanting 120 dollars, find
a similar DC wall power supply with output spec near 10-11 VDC
( similar current rating capability) and adapt the power plugs (cut
off and rewire the old to new one), and your problem is solved.

This is excellent advice assuming you actually measure the resultant
charge current. And assuming the power supply does not attempt to
power the device, and, and. Last thing you want is a fire due to very
poor choice of power brick. It's trivial if you know what you're doing.
Not so trivial if you don't.
That the question was asked implies the latter.

Better to fix the busted one and remove the risk...assuming you measure
the resultant charge current, and, and...
mike
I claim to know what I'm doing...ask me about my singed eyebrows...

 

[[email protected]]

Hello all and again, thanks for your help. I have replaced the LED on
the battery charger, hooked it up to the battery pack and the voltage
now show 9.42 VDC. I'll let it recharge, but I expect everything to
work correctly now.

I am a happy camper and thankful for the advise that this group
provided.