NiCad SpotWelder?

[mike]

S.M.Taylor wrote:

mike wrote:


You need to try VERY hard to minimize leakage inductance in your
transformer. There are also satuation issues. A microwave oven
transformer is designed specifically for LOTS of leakage inductance,
then they put shunts in to make it higher still. Not a good starting
point for a CD welder. But makes an OK brute force 60 Hz. welder.


That's rather the conclusion I had come to as well !


If you're doing serious welding, you need to make me an offer
on my small welding head. It's a Unitek model 32.
A good repeatable welding head is half the battle.


Our head is an opposed pincer type thing, arranged a bit like a toggle
clamp.

Thanks for tbe tips - so no-one has made a proper pulse discharge
welder, apart from the big guys ?

Steve

I think if you had the transformer, the rest would be easy.
Note that the data in my previous post showed discharge into one
milliohm. My experimental secondary path had 20 or so milliohms.
That doesn't even count the effects of poor coupling. I was taking
out a milliohm here and there.
I was actually welding battery tabs with a controlled cycle counter
off AC, but repeatability was poor.

I gave up trying to switch a low voltage cap discharge. I welded a lot
of switch contacts, but never a battery tab. I was starting to think
about switching high voltage into a transformer when the Unitek 125
showed up on Ebay for $15.
That sorta killed my enthusiam for further experiments.

Welding with an opposed head is significantly easier.
mike

--
Return address is VALID.
Bunch of stuff For Sale and Wanted at the link below.
Toshiba & Compaq LiIon Batteries, Test Equipment
Honda CB-125S $800 in PDX
Yaesu FTV901R Transverter, 30pS pulser
Tektronix Concept Books, spot welding head...
http://www.geocities.com/SiliconValley/Monitor/4710/

 

[Watson A.Name - \"Watt Su]

"mike" <spamme0@juno.com> wrote in message
news:40577F2E.1080304@juno.com...

Watson A.Name \"Watt Sun - the Dark Remover\" wrote:
MikeM wrote:

Anybody build a welder capable of spot welding
tabs on batteries?

I came into a bunch of tabless NiCads, and would like to
attach tabs.


MikeM


Google for microwave oven welder and you will come up with a
homemade
spot welder that can weld even thicker metal than NiCad battery
tabs.

Can you be just a wee bit more specific. Google for "microwave oven
welder" got one hit to a dead site. Without the quotes got 4620 hits
to all sorts of stuff. To which were you refering?
Thanks, mike

The second one. Teralabs spot welder.

> --

 

[Watson A.Name - \"Watt Su]

<ehsjr@bellatlantic.net> wrote in message
news:4057D5E7.3B76A1FF@bellatlantic.net...

Dave VanHorn wrote:

I just solder directly to the battery, I tin it first, then solder
either
a tab (ie:
keystone makes all sorts of PCB mount tabs), but this all depends
on how
many you need to
make.

http://www.dvanhorn.org/NIMH/Index.php

This is a very bad idea, though I know people do it all the time.
The cell makers cringe when they hear stuff like this.

If it's a choice between soldering the cell or throwing
it away, the "very bad idea" becomes a very good idea.

Just don't use any of the cells in something that demands high
reliability, like a (GULP!) pacemaker.

That doesn't change the fact that you can harm the cell
by soldering, but soldering a single cell into a 35
dollar pack is worth the chance to save the pack.

Nowadays, the packs can cost a hundred or two.

 

[mike]

Watson A.Name - \"Watt Sun, the Dark Remover\" wrote:

"mike" <spamme0@juno.com> wrote in message
news:40577F2E.1080304@juno.com...

Watson A.Name \"Watt Sun - the Dark Remover\" wrote:

MikeM wrote:


Anybody build a welder capable of spot welding
tabs on batteries?

I came into a bunch of tabless NiCads, and would like to
attach tabs.


MikeM


Google for microwave oven welder and you will come up with a

homemade

spot welder that can weld even thicker metal than NiCad battery

tabs.

Can you be just a wee bit more specific. Google for "microwave oven
welder" got one hit to a dead site. Without the quotes got 4620 hits
to all sorts of stuff. To which were you refering?
Thanks, mike


The second one. Teralabs spot welder.

Well...it's the third one on my search list. If people have info,

why can't they just post the D$#%W$ LINK?? Then we know that we're
discussing the same apple. A general google search is darn near useless
as a reference unless it gets one hit on everybody's search.

Take a look at the weld pictures. If you get the top of your battery
hot enough to discolor it, it's too hot.

If you use the right version of the solid state relay, it starts on zero
crossing, greatly reducing stress on the components. I also used a
PAL20V8 to implement a full-cycle counter to terminate the weld on the
correct half cycle and reduce saturation effects. I'd probably use a
PIC if I rebuilt it. I was finding that
with only a few cycles of weld time, the previous state of the
transformer mattered.

mike


--
Return address is VALID.
Bunch of stuff For Sale and Wanted at the link below.
Toshiba & Compaq LiIon Batteries, Test Equipment
Honda CB-125S $800 in PDX
Yaesu FTV901R Transverter, 30pS pulser
Tektronix Concept Books, spot welding head...
http://www.geocities.com/SiliconValley/Monitor/4710/

 

[ddwyer]

In article <405D9837.8080201@juno.com>, mike <spamme0@juno.com> writes

Watson A.Name - \"Watt Sun, the Dark Remover\" wrote:
"mike" <spamme0@juno.com> wrote in message
news:40577F2E.1080304@juno.com...

Watson A.Name \"Watt Sun - the Dark Remover\" wrote:

MikeM wrote:


Anybody build a welder capable of spot welding
tabs on batteries?

I came into a bunch of tabless NiCads, and would like to
attach tabs.


MikeM


Google for microwave oven welder and you will come up with a

homemade

spot welder that can weld even thicker metal than NiCad battery

tabs.

Can you be just a wee bit more specific. Google for "microwave oven
welder" got one hit to a dead site. Without the quotes got 4620 hits
to all sorts of stuff. To which were you refering?
Thanks, mike


The second one. Teralabs spot welder.

Well...it's the third one on my search list. If people have info,
why can't they just post the D$#%W$ LINK?? Then we know that we're
discussing the same apple. A general google search is darn near useless
as a reference unless it gets one hit on everybody's search.

Take a look at the weld pictures. If you get the top of your battery
hot enough to discolor it, it's too hot.

If you use the right version of the solid state relay, it starts on zero
crossing, greatly reducing stress on the components. I also used a
PAL20V8 to implement a full-cycle counter to terminate the weld on the
correct half cycle and reduce saturation effects. I'd probably use a
PIC if I rebuilt it. I was finding that
with only a few cycles of weld time, the previous state of the
transformer mattered.

mike


Coming into this late.

Have used parallel gap welder with both cap discharge and direct mains
stepdown transformer.
Material compatibility is almost everything.
So molybdenum copper electrodes stick least with nickel as per
batteries.
Control of Actual force between electrodes and weld subject.
is essential
--
ddwyer

 

mike wrote:

ehsjr@bellatlantic.net wrote:

Dave VanHorn wrote:

I just solder directly to the battery, I tin it first, then solder either

a tab (ie:

keystone makes all sorts of PCB mount tabs), but this all depends on how

many you need to

make.

http://www.dvanhorn.org/NIMH/Index.php

This is a very bad idea, though I know people do it all the time.
The cell makers cringe when they hear stuff like this.


If it's a choice between soldering the cell or throwing
it away, the "very bad idea" becomes a very good idea.

That doesn't change the fact that you can harm the cell
by soldering, but soldering a single cell into a 35
dollar pack is worth the chance to save the pack.

Under the heading, "Sounded like a good idea at the time"
One of my early attempts to rebuild a laptop battery pack
resulted in some sizzling noise coming from my computer.
I managed to get the battery out and into the front yard
before it exploded. Luckily, the cell went the other direction
and all I got was hot caustic goo on my safety glasses and some
minor facial burns.

How on earth did you screw things up so badly
that a disconnected battery pack exploded?
I'm trying to imagine the circuit that would do
that. A shorted cell wouldn't do it. An open
cell wouldn't do it. A cell installed backwards
wouldn't do it. There must've been something in
addition to one of those defects - or some defect
or defects not included in those mentioned.

So, how much is your laptop worth?
How about your kid's eyesight?
Make sure you include ALL the facts when making your decision.
If that soldering iron melts the safety vent shut, you're in for
trouble.
mike

ps Don't get me started on the perils of replacing one cell of
a multi-cell pack.

--
Return address is VALID.
Bunch of stuff For Sale and Wanted at the link below.
Toshiba & Compaq LiIon Batteries, Test Equipment
Honda CB-125S $800 in PDX
Yaesu FTV901R Transverter, 30pS pulser
Tektronix Concept Books, spot welding head...
http://www.geocities.com/SiliconValley/Monitor/4710/

 

[John Woodgate]

I read in sci.electronics.design that ehsjr@bellatlantic.net wrote (in
<40626882.BF3A8928@bellatlantic.net&gt about 'NiCad SpotWelder?', on Thu,
25 Mar 2004:

How on earth did you screw things up so badly that a disconnected
battery pack exploded? I'm trying to imagine the circuit that would do
that. A shorted cell wouldn't do it. An open cell wouldn't do it. A cell
installed backwards wouldn't do it.

A cell installed backwards would be charged in reverse by the other
cells. They can explode. Guess how I know. I have a shaver that uses
cells in parallel!
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

 

[Dave VanHorn]

How on earth did you screw things up so badly
that a disconnected battery pack exploded?
I'm trying to imagine the circuit that would do
that. A shorted cell wouldn't do it. An open
cell wouldn't do it. A cell installed backwards
wouldn't do it. There must've been something in
addition to one of those defects - or some defect
or defects not included in those mentioned.

There is something called "thermal runaway".
In cells with damaged or missing vents, it is possible for the cell to
accumulate both hydrogen and oxygen under pressure. The results are rather
spectacular. On my web page, you can see a single cell event. I've seen
worse, but I can't release that data at this time.

 

[mike]

ehsjr@bellatlantic.net wrote:

mike wrote:

snip
How on earth did you screw things up so badly
that a disconnected battery pack exploded?
I'm trying to imagine the circuit that would do
that. A shorted cell wouldn't do it. An open
cell wouldn't do it. A cell installed backwards
wouldn't do it. There must've been something in
addition to one of those defects - or some defect
or defects not included in those mentioned.

Wasn't hard at all. This was an early attempt at patching up
a NiMH battery. I replaced the cells with ones that (apparently)
couldn't take the fast charge in the laptop. I pulled them out of a
different pack,
cut the welded tabs in half and soldered the tabs together in the new
configuration. I tested the crap out of it by fast
charge/discharging it on the bench for several cycles.

And I DO mean "tested the crap out of it". I built a
custom computer controlled test fixture out of a GPIB programmable
power supply and dynamic load fixture. I plotted graphs of volts/time
and capacity. I was VERY SURE I knew what I was doing.

When I tried to charge it in the laptop, it overheated and started to
hiss. I ripped out the pack and hauled it into the front yard.

After a few seconds it stopped hissing. Good! A few seconds later, one
cell exploded. I never thought I could be so happy that I could still
see the hot caustic goo on my safety glasses. And I still had my whole
body intact.
I never did find the guts of the cell.

The laptop used a thermistor for charge termination. There was enough
imbalance in the cells to allow one to overheat before the ones under
the thermistor warmed up.

Mr. Murphy doesn't seem to care how many EE degrees you have or how many
decades of analog design experience you have. I cringe every time I
read how a newbie is gonna solder some batteries together. Yeah, it
often works. I had one explosion in over 40 years of messing with
batteries. A very small percentage, but it only takes once to hurt
yourself real bad. Remember that many of us have been abusing surplus
NiCd cells that were made in the '70s. The energy density of modern
batteries is MUCH higher. Soldering batteries is VERY risky even if
they're NOT lithium.
mike

So, how much is your laptop worth?
How about your kid's eyesight?
snip

--
Return address is VALID.
Bunch of stuff For Sale and Wanted at the link below.
Toshiba & Compaq LiIon Batteries, Test Equipment
Honda CB-125S $800 in PDX
Yaesu FTV901R Transverter, 30pS pulser
Tektronix Concept Books, spot welding head...
http://www.geocities.com/SiliconValley/Monitor/4710/

 

John Woodgate wrote:

I read in sci.electronics.design that ehsjr@bellatlantic.net wrote (in
40626882.BF3A8928@bellatlantic.net&gt about 'NiCad SpotWelder?', on Thu,
25 Mar 2004:
How on earth did you screw things up so badly that a disconnected
battery pack exploded? I'm trying to imagine the circuit that would do
that. A shorted cell wouldn't do it. An open cell wouldn't do it. A cell
installed backwards wouldn't do it.

A cell installed backwards would be charged in reverse by the other
cells.

Yes - if the thing is in circuit, but not when the
pack is disconnected.

They can explode. Guess how I know. I have a shaver that uses
cells in parallel!

I don't doubt that. Haven't had that "pleasure" myself,
and hope I won't!

--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

 

mike wrote:

ehsjr@bellatlantic.net wrote:

mike wrote:

snip
How on earth did you screw things up so badly
that a disconnected battery pack exploded?
I'm trying to imagine the circuit that would do
that. A shorted cell wouldn't do it. An open
cell wouldn't do it. A cell installed backwards
wouldn't do it. There must've been something in
addition to one of those defects - or some defect
or defects not included in those mentioned.

Wasn't hard at all. This was an early attempt at patching up
a NiMH battery. I replaced the cells with ones that (apparently)
couldn't take the fast charge in the laptop. I pulled them out of a
different pack,
cut the welded tabs in half and soldered the tabs together in the new
configuration. I tested the crap out of it by fast
charge/discharging it on the bench for several cycles.

And I DO mean "tested the crap out of it". I built a
custom computer controlled test fixture out of a GPIB programmable
power supply and dynamic load fixture. I plotted graphs of volts/time
and capacity. I was VERY SURE I knew what I was doing.

When I tried to charge it in the laptop, it overheated and started to
hiss. I ripped out the pack and hauled it into the front yard.

After a few seconds it stopped hissing. Good! A few seconds later, one
cell exploded. I never thought I could be so happy that I could still
see the hot caustic goo on my safety glasses. And I still had my whole
body intact.
I never did find the guts of the cell.

The laptop used a thermistor for charge termination. There was enough
imbalance in the cells to allow one to overheat before the ones under
the thermistor warmed up.

Mr. Murphy doesn't seem to care how many EE degrees you have or how many
decades of analog design experience you have. I cringe every time I
read how a newbie is gonna solder some batteries together. Yeah, it
often works. I had one explosion in over 40 years of messing with
batteries. A very small percentage, but it only takes once to hurt
yourself real bad. Remember that many of us have been abusing surplus
NiCd cells that were made in the '70s. The energy density of modern
batteries is MUCH higher. Soldering batteries is VERY risky even if
they're NOT lithium.
mike

Bizarre! I would not have thought a cell could explode
once the pack was removed from the circuit, unless there
was a short somewhere allowing the other cells to force
a current through the cell. Is it possible that the
cell leaked and provided that short? I don't know if
enough was left of the pack to determine that.

 

[mike]

ehsjr@bellatlantic.net wrote:

mike wrote:

ehsjr@bellatlantic.net wrote:

mike wrote:


snip

How on earth did you screw things up so badly
that a disconnected battery pack exploded?
I'm trying to imagine the circuit that would do
that. A shorted cell wouldn't do it. An open
cell wouldn't do it. A cell installed backwards
wouldn't do it. There must've been something in
addition to one of those defects - or some defect
or defects not included in those mentioned.

Wasn't hard at all. This was an early attempt at patching up
a NiMH battery. I replaced the cells with ones that (apparently)
couldn't take the fast charge in the laptop. I pulled them out of a
different pack,
cut the welded tabs in half and soldered the tabs together in the new
configuration. I tested the crap out of it by fast
charge/discharging it on the bench for several cycles.

And I DO mean "tested the crap out of it". I built a
custom computer controlled test fixture out of a GPIB programmable
power supply and dynamic load fixture. I plotted graphs of volts/time
and capacity. I was VERY SURE I knew what I was doing.

When I tried to charge it in the laptop, it overheated and started to
hiss. I ripped out the pack and hauled it into the front yard.

After a few seconds it stopped hissing. Good! A few seconds later, one
cell exploded. I never thought I could be so happy that I could still
see the hot caustic goo on my safety glasses. And I still had my whole
body intact.
I never did find the guts of the cell.

The laptop used a thermistor for charge termination. There was enough
imbalance in the cells to allow one to overheat before the ones under
the thermistor warmed up.

Mr. Murphy doesn't seem to care how many EE degrees you have or how many
decades of analog design experience you have. I cringe every time I
read how a newbie is gonna solder some batteries together. Yeah, it
often works. I had one explosion in over 40 years of messing with
batteries. A very small percentage, but it only takes once to hurt
yourself real bad. Remember that many of us have been abusing surplus
NiCd cells that were made in the '70s. The energy density of modern
batteries is MUCH higher. Soldering batteries is VERY risky even if
they're NOT lithium.
mike



Bizarre! I would not have thought a cell could explode
once the pack was removed from the circuit, unless there
was a short somewhere allowing the other cells to force
a current through the cell. Is it possible that the
cell leaked and provided that short? I don't know if
enough was left of the pack to determine that.

When the cell overheats, the separator can fail letting the + and - touch.
Then all the energy stored in the cell goes directly into melting more
separator and vaporizing the
electrolyte. The cell gets very hot very fast...if you're lucky and
it's not a Lithium and it doesn't catch fire... This opens the vent and
sprays electrolyte all over the place...if you're lucky. If you're not
lucky, debris from the disintegrating internal structure gets blown into
the vent and plugs it up. Then guess what happens. Stopping of the
hissing sound is NOT a good thing.

Soldering overheats the cell possibly damaging the separator, possibly
leading to explosion now or at a later stressful event.

SOLDERING RECHARGEABLE BATTERIES IS BAD!!!!!
Yes, it can be done. Yes, I've done it successfully. No, I won't do it
again.

MIKE

--
Return address is VALID.
Bunch of stuff For Sale and Wanted at the link below.
Toshiba & Compaq LiIon Batteries, Test Equipment
Honda CB-125S $800 in PDX
Yaesu FTV901R Transverter, 30pS pulser
Tektronix Concept Books, spot welding head...
http://www.geocities.com/SiliconValley/Monitor/4710/

 

[CWatters]

<ehsjr@bellatlantic.net> wrote in message
news:40637EFD.5CAB9D0E@bellatlantic.net...

Yes - if the thing is in circuit, but not when the
pack is disconnected.

What sometimes happens is that on charge a pack cets so hot that the makers
shrink sleeve splits. Then cell cans short against each other and the rest
is obvious.

 

CWatters wrote:

ehsjr@bellatlantic.net> wrote in message
news:40637EFD.5CAB9D0E@bellatlantic.net...

Yes - if the thing is in circuit, but not when the
pack is disconnected.

What sometimes happens is that on charge a pack cets so hot that the makers
shrink sleeve splits. Then cell cans short against each other and the rest
is obvious.

Thanks! That makes sense.