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another odd battery problem
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William Sommerwerck
Jan 9, 2014, 8:15:09 AM1/9/14
to
Any nicad experts out there? This is an interesting one. (I'm not looking for
a "solution", just an explanation, out of curiosity.)
Many years ago I bought the Sony TCD-D3 DAT Walkman, which fits a fat pocket.
I made a few live recordings, as it was a lot less bulky than a processor/VCR
system.
The other day I pulled it out to confirm it was still working. I'd bought two
extra batteries with the unit, and put all three on charge. They all charged
up, but the third battery wouldn't power the unit. Its end-of-charge voltage
was nearly 7V (though these batteries are nominally 6V), and the other two
charged to about 6.4V.
When I put the third battery on charge again, it rose to about 7.5V, even
before charge was terminated. I let it sit overnight, and it self-discharged
(?) to about 5.5V. (The others //did not// show significant self-discharge.)
It still wouldn't power the unit.
"Obviously" this battery pack is defective. I'm just wondering if anyone knows
what's going on.
It's no big deal, as I have two good packs (which are 20+ years old!), and the
AC adapter. Also, the packs are "external", so I could (if I wanted) saw open
the pack and replace the cells. Or simply throw together a homebrew pack to
fit the DC jack.
Just askin'.
"We already know the answers -- we just haven't asked the right questions."
-- Edwin Land
a "solution", just an explanation, out of curiosity.)
Many years ago I bought the Sony TCD-D3 DAT Walkman, which fits a fat pocket.
I made a few live recordings, as it was a lot less bulky than a processor/VCR
system.
The other day I pulled it out to confirm it was still working. I'd bought two
extra batteries with the unit, and put all three on charge. They all charged
up, but the third battery wouldn't power the unit. Its end-of-charge voltage
was nearly 7V (though these batteries are nominally 6V), and the other two
charged to about 6.4V.
When I put the third battery on charge again, it rose to about 7.5V, even
before charge was terminated. I let it sit overnight, and it self-discharged
(?) to about 5.5V. (The others //did not// show significant self-discharge.)
It still wouldn't power the unit.
"Obviously" this battery pack is defective. I'm just wondering if anyone knows
what's going on.
It's no big deal, as I have two good packs (which are 20+ years old!), and the
AC adapter. Also, the packs are "external", so I could (if I wanted) saw open
the pack and replace the cells. Or simply throw together a homebrew pack to
fit the DC jack.
Just askin'.
"We already know the answers -- we just haven't asked the right questions."
-- Edwin Land
Dave M
Jan 9, 2014, 12:46:15 PM1/9/14
to
Nicads have historically been plagued by "dendrites", or crystals of
conductive material (probably cadmium, but not sure) between the electrolyte
layers in the cells. This creates a low resistance leakage path inside the
cells, rendering them incapable of retaining a charge for any length of time
or putting out their rated voltage. Dendrites are responsible for the
so-called "memory effect" that nicads are famous for.
There have been several procedures published on the net as to how to remove
dendrites (search for "nicad dendrites"). One process involves charging a
large electrolytic capacitor (eg., 500uF) to a few hundred volts,
discharging it through the bad cell, then running the cell through a couple
of charge/discharge cycles. I built a little box for this process several
years ago, and it seems to work. It consists of a transformer, a voltage
doubler, and a large capacitor. A push-button switch triggers an SCR that
lets the capacitor discharge into the bad cell (sort of like a one-shot CD
ignition)
Dave M
et...@whidbey.com
Jan 9, 2014, 7:05:17 PM1/9/14
to
nicads he had. And he said they now charge prpperly and hold a charge.
He's happy.
Eric
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William Sommerwerck
Jan 9, 2014, 7:47:19 PM1/9/14
to
"Dave M" wrote in message
news:7-GdnRWXTpL1fVPP...@giganews.com...
> Nicads have historically been plagued by "dendrites", or crystals of
> conductive material (probably cadmium, but not sure) between the
> electrolyte layers in the cells. This creates a low resistance leakage
> path inside the cells, rendering them incapable of retaining a charge
> for any length of time or putting out their rated voltage. Dendrites are
> responsible for the so-called "memory effect" that nicads are famous for.
> There have been several procedures published on the net as to how to
> remove dendrites (search for "nicad dendrites"). One process involves
> charging a large electrolytic capacitor (eg, 500uF) to a few hundred volts,
> I built a little box for this process several years ago, and it seems to
> work.
> It consists of a transformer, a voltage doubler, and a large capacitor.
> A push-button switch triggers an SCR that lets the capacitor discharge into
> the bad cell (sort of like a one-shot CD ignition).
I'll give this serious thought. The worst that can happen is that the battery
is ruined. (!!!) Thanks.
I'm still curious about the battery's unnaturally high voltage.
news:7-GdnRWXTpL1fVPP...@giganews.com...
> Nicads have historically been plagued by "dendrites", or crystals of
> conductive material (probably cadmium, but not sure) between the
> electrolyte layers in the cells. This creates a low resistance leakage
> path inside the cells, rendering them incapable of retaining a charge
> for any length of time or putting out their rated voltage. Dendrites are
> responsible for the so-called "memory effect" that nicads are famous for.
> There have been several procedures published on the net as to how to
> remove dendrites (search for "nicad dendrites"). One process involves
> discharging it through the bad cell, then running the cell through a couple
> of charge/discharge cycles.
I assume the discharge is + to +.
> of charge/discharge cycles.
> I built a little box for this process several years ago, and it seems to
> work.
> It consists of a transformer, a voltage doubler, and a large capacitor.
> A push-button switch triggers an SCR that lets the capacitor discharge into
I'll give this serious thought. The worst that can happen is that the battery
is ruined. (!!!) Thanks.
I'm still curious about the battery's unnaturally high voltage.
Phil Allison
Jan 9, 2014, 10:28:38 PM1/9/14
to
"William Sommerwanker "
>
> When I put the third battery on charge again, it rose to about 7.5V, even
> before charge was terminated. I let it sit overnight, and it
> self-discharged (?) to about 5.5V. (The others //did not// show
> significant self-discharge.) It still wouldn't power the unit.
>
> "Obviously" this battery pack is defective. I'm just wondering if anyone
> knows what's going on.
** You are describing the standard "old age" failure mode of most NiCds.
> When I put the third battery on charge again, it rose to about 7.5V, even
> before charge was terminated. I let it sit overnight, and it
> self-discharged (?) to about 5.5V. (The others //did not// show
> significant self-discharge.) It still wouldn't power the unit.
>
> "Obviously" this battery pack is defective. I'm just wondering if anyone
> knows what's going on.
1. The internal resistance of some or all the cells in a pack rises - often
dramatically.
2. The energy capacity drops by a large factor.
3. The pack will not hold charge due to internal leakage.
4. The terminal voltage is depressed, from 1.25V to about 1.2V per cell.
A single overheating event can result in the same outcome - whether by
overcharging or otherwise.
Reason ?
NiCd cells have a small amount of water in them - lose that and the cell is
stuffed.
... Phil
Phil Allison
Jan 9, 2014, 10:36:20 PM1/9/14
to
"Phil Allison"
> 4. The terminal voltage is depressed, from 1.25V to about 1.1V per cell.
... Phil
mike
Jan 9, 2014, 11:45:21 PM1/9/14
to
On 1/9/2014 4:47 PM, William Sommerwerck wrote:
> "Dave M" wrote in message
> news:7-GdnRWXTpL1fVPP...@giganews.com...
>
>> Nicads have historically been plagued by "dendrites", or crystals of
>> conductive material (probably cadmium, but not sure) between the
>> electrolyte layers in the cells. This creates a low resistance leakage
>> path inside the cells, rendering them incapable of retaining a charge
>> for any length of time or putting out their rated voltage. Dendrites are
>> responsible for the so-called "memory effect" that nicads are famous for.
>
>> There have been several procedures published on the net as to how to
>> remove dendrites (search for "nicad dendrites"). One process involves
>> charging a large electrolytic capacitor (eg, 500uF) to a few hundred
>> volts, discharging it through the bad cell, then running the cell
>> through a couple of charge/discharge cycles.
>
> I assume the discharge is + to +.
>
I'd be careful. Energy is proportional to the square of the voltage.
> "Dave M" wrote in message
> news:7-GdnRWXTpL1fVPP...@giganews.com...
>
>> Nicads have historically been plagued by "dendrites", or crystals of
>> conductive material (probably cadmium, but not sure) between the
>> electrolyte layers in the cells. This creates a low resistance leakage
>> path inside the cells, rendering them incapable of retaining a charge
>> for any length of time or putting out their rated voltage. Dendrites are
>> responsible for the so-called "memory effect" that nicads are famous for.
>
>> There have been several procedures published on the net as to how to
>> remove dendrites (search for "nicad dendrites"). One process involves
>> charging a large electrolytic capacitor (eg, 500uF) to a few hundred
>> volts, discharging it through the bad cell, then running the cell
>> through a couple of charge/discharge cycles.
>
> I assume the discharge is + to +.
>
I use 12,000 uF and 10-20V, mostly because that's what was handy.
You want to hit the sweet spot where you instantly vaporize the dendrite,
but generate no more heat than necessary. Too little energy or too
much energy is worse than just right. That's why suggestions to
use a car battery are bad. Little chance of getting it just right.
Way too much chance of getting enough energy to explode something.
500uF AND 200V is WAY too much.
The process leaves the hole in the insulator/separator.
The field density is high and the dendrite wants to grow back.
And discharge thru the hole causes the high self-discharge rate.
I've had a lot of success restoring 40 year old F-NiCd's for
uses that don't require more than a few days storage life.
But, these days, you can get equivalent capacity in a pair of
AA NiMH cells.
Don't discount the safety issues with high voltage.
The "experts" who look at only part of the problem will call me an idiot,
because 200V probably won't kill you.
Two problems with that..."probably" is great for statistics, but
provides little solace to your family when you're the ONE who died.
And B, the shock isn't the only problem.
I've got scars where the muscle contractions that thru me across the
room caused me to rip my arm open on some sharp object in the path.
Luckily, I haven't fallen and cracked my head open on the furniture...
yet...
Eye Protection is a MUST. Sparks fly.
William Sommerwerck
Jan 10, 2014, 3:42:49 AM1/10/14
to
Fine. Nothing new. But why the high voltage?
Phil Allison
Jan 10, 2014, 4:39:52 AM1/10/14
to
"William Sommerwanker the Over Snipper form HELL "
> Fine. Nothing new.
** All new to YOU fuckhead.
> But why the high voltage?
Cease charge the pack and the voltage drops almost immediately.
V = I x R ..........
Wot an idiot.
.... Phil
Dave M
Jan 10, 2014, 7:04:24 AM1/10/14
to
William Sommerwerck wrote:
> "Dave M" wrote in message
> news:7-GdnRWXTpL1fVPP...@giganews.com...
>
>
> "Dave M" wrote in message
> news:7-GdnRWXTpL1fVPP...@giganews.com...
>
>
>> There have been several procedures published on the net as to how to
>> remove dendrites (search for "nicad dendrites"). One process involves
>> charging a large electrolytic capacitor (eg, 500uF) to a few hundred
>> volts, discharging it through the bad cell, then running the cell
>> through a couple of charge/discharge cycles.
>
> I assume the discharge is + to +.
>
>
>> I built a little box for this process several years ago, and it
>> seems to work.
>> It consists of a transformer, a voltage doubler, and a large
>> capacitor. A push-button switch triggers an SCR that lets the capacitor
>> discharge into the bad cell (sort of like a one-shot CD ignition).
>
>
> I'll give this serious thought. The worst that can happen is that the
> battery is ruined. (!!!) Thanks.
Yes, + to + on the CD pulse and normal charge/discharge.
>> remove dendrites (search for "nicad dendrites"). One process involves
>> charging a large electrolytic capacitor (eg, 500uF) to a few hundred
>> volts, discharging it through the bad cell, then running the cell
>> through a couple of charge/discharge cycles.
>
> I assume the discharge is + to +.
>
>
>> I built a little box for this process several years ago, and it
>> seems to work.
>> It consists of a transformer, a voltage doubler, and a large
>> capacitor. A push-button switch triggers an SCR that lets the capacitor
>> discharge into the bad cell (sort of like a one-shot CD ignition).
>
>
> I'll give this serious thought. The worst that can happen is that the
> battery is ruined. (!!!) Thanks.
Dave M
William Sommerwerck
Jan 10, 2014, 9:40:56 AM1/10/14
to
"Phil Allison" wrote in message news:bj9tfj...@mid.individual.net...
> Fine. Nothing new.
** All new to YOU, fuckhead.
I've killed men for less than that.
I wasn't expecting you to repeat common knowledge about rechargeable
batteries.
> But why the high voltage?
** When on charge - point 1 applies.
** Cease charge the pack and the voltage drops almost immediately.
** V = I x R ..........
** Wot an idiot.
You don't see it, do you? Of course not.
The same thought crossed my mind. The question is... why should a cell's
voltage -- which is supposedly determined by the battery's chemistry --
essentially double (assuming only one cell is bad)? Why should the cell become
a sort of electrochemical chameleon, trying to match the voltage across it?
> Fine. Nothing new.
** All new to YOU, fuckhead.
I've killed men for less than that.
I wasn't expecting you to repeat common knowledge about rechargeable
batteries.
> But why the high voltage?
** When on charge - point 1 applies.
** V = I x R ..........
** Wot an idiot.
You don't see it, do you? Of course not.
The same thought crossed my mind. The question is... why should a cell's
voltage -- which is supposedly determined by the battery's chemistry --
essentially double (assuming only one cell is bad)? Why should the cell become
a sort of electrochemical chameleon, trying to match the voltage across it?
Phil Allison
Jan 10, 2014, 7:29:04 PM1/10/14
to
"William Sommerwanker"
>> Fine. Nothing new.
>
> ** All new to YOU, fuckhead.
>
> I've killed men for less than that.
> I wasn't expecting you to repeat common knowledge about rechargeable
> batteries.
To your claim of "odd battery problem" - I replied:
--------------------------------------------------------------------------------
You are describing the standard "old age" failure mode of most NiCds.
1. The internal resistance of some or all the cells in a pack rises - often
dramatically.
2. The energy capacity drops by a large factor.
3. The pack will not hold charge due to internal leakage.
4. The terminal voltage is depressed, from 1.25V to about 1.2V per cell.
A single overheating event can result in the same outcome - whether by
overcharging or otherwise.
Reason ?
NiCd cells have a small amount of water in them - lose that and the cell is
stuffed.
** The above is NOT common knowledge and is ONLY true of NiCd cells.
>> But why the high voltage?
>
> ** When on charge - point 1 applies.
> ** Cease charge the pack and the voltage drops almost immediately.
> ** V = I x R ..........
> ** Wot an idiot.
>
> You don't see it, do you? Of course not.
> The same thought crossed my mind. The question is... why should a cell's
> voltage -- which is supposedly determined by the battery's chemistry --
> essentially double (assuming only one cell is bad)?
Not only do you over snip and change context at whim - now invent entirely
new stuff and pretend it is not new.
FYI fuckwit:
YOU claimed to have three 6V NiCd packs - means 5 cells in each.
So the normal, rest voltage is 1.25V x 5 = 6.25V
On charge, with good cells and at the recommended rate, voltage peaks to
about 1.45V then falls to about 1.35V per cell.
That means the pack will rise to 7.25V then fall to 6.75V as the cells get
warm.
If the cells are old and bad, the voltage will rise higher and may never
fall while on charge.
At rest the same faulty pack may well drop to a 1.1V per cell = 5.5V.
This correlates with your story, 100%.
Nothing odd, totally normal.
Shame the same is NOT true of steaming great fuckwits like YOU !!!!!!!!!!
... Phil
William Sommerwerck
Jan 10, 2014, 8:01:19 PM1/10/14
to
"Phil Allison" wrote in message news:bjbhir...@mid.individual.net...
** The above is NOT common knowledge and is ONLY true of NiCd cells.
It's common knowledge to anyone with a technical background.
> That means the pack will rise to 7.25V then fall to 6.75V as the cells
> get warm.
But it went to something like 7.8V. The question still hasn't been answered.
The fact that the pack is labeled 6V doesn't mean it has five cells in it.
Probably the best thing to do is Dremel off the top of the bad pack, and see
what's going on.
** The above is NOT common knowledge and is ONLY true of NiCd cells.
> That means the pack will rise to 7.25V then fall to 6.75V as the cells
> get warm.
The fact that the pack is labeled 6V doesn't mean it has five cells in it.
Probably the best thing to do is Dremel off the top of the bad pack, and see
what's going on.
Phil Allison
Jan 10, 2014, 8:45:48 PM1/10/14
to
"William Sommerwanker"
>> Fine. Nothing new.
>
> ** All new to YOU, fuckhead.
>
> I've killed men for less than that.
** Another idiotic lie.
> I wasn't expecting you to repeat common knowledge about rechargeable
> batteries.
** And I didn't.
To your claim of "odd battery problem" - I replied:
--------------------------------------------------------------------------------
You are describing the standard "old age" failure mode of most NiCds.
1. The internal resistance of some or all the cells in a pack rises - often
dramatically.
2. The energy capacity drops by a large factor.
3. The pack will not hold charge due to internal leakage.
4. The terminal voltage is depressed, from 1.25V to about 1.2V per cell.
A single overheating event can result in the same outcome - whether by
overcharging or otherwise.
Reason ?
NiCd cells have a small amount of water in them - lose that and the cell is
stuffed.
------------------------------------------------------------------------------------
** The above is NOT common knowledge and is ONLY true of NiCd cells.
>> But why the high voltage?
>
> ** When on charge - point 1 applies.
> ** Cease charge the pack and the voltage drops almost immediately.
> ** V = I x R ..........
> ** Wot an idiot.
>
> You don't see it, do you? Of course not.
** There is nothing new or "odd" to see.
> The same thought crossed my mind. The question is... why should a cell's
> voltage -- which is supposedly determined by the battery's chemistry --
> essentially double (assuming only one cell is bad)?
** You never put that **fucking mad idea** forward before ??????
Not only do you over snip and change context at whim - now invent entirely
new stuff and pretend it is not new.
FYI fuckwit:
YOU claimed to have three 6V NiCd packs - means 5 cells in each.
So the normal, rest voltage is 1.25V x 5 = 6.25V
On charge, with good cells and at the recommended rate, voltage peaks to
about 1.45V then falls to about 1.35V per cell.
>
> ** When on charge - point 1 applies.
> ** Cease charge the pack and the voltage drops almost immediately.
> ** V = I x R ..........
> ** Wot an idiot.
>
> You don't see it, do you? Of course not.
** There is nothing new or "odd" to see.
> The same thought crossed my mind. The question is... why should a cell's
> voltage -- which is supposedly determined by the battery's chemistry --
> essentially double (assuming only one cell is bad)?
** You never put that **fucking mad idea** forward before ??????
Not only do you over snip and change context at whim - now invent entirely
new stuff and pretend it is not new.
FYI fuckwit:
YOU claimed to have three 6V NiCd packs - means 5 cells in each.
So the normal, rest voltage is 1.25V x 5 = 6.25V
On charge, with good cells and at the recommended rate, voltage peaks to
about 1.45V then falls to about 1.35V per cell.
That means the pack will rise to 7.25V then fall to 6.75V as the cells get
warm.
warm.
William Sommerwerck
Jan 11, 2014, 3:49:55 PM1/11/14
to
I attacked the "bad" Sony battery pack with a Dremel-powered cutoff disk. It
was stuffed with five huge prism cells, each measuring 3 x 7/8 x 1/4. At least
two of them appeared to have excessively low voltage.
I have no intention of trying to restore or replace these cells, especially as
they aren't interconnected in the way you'd expect.
The question remains... As nicads and NiMH cells are charged by constant
current (theoretically, anyway), what would cause the total post-charge
voltage to hit nearly eight volts?
was stuffed with five huge prism cells, each measuring 3 x 7/8 x 1/4. At least
two of them appeared to have excessively low voltage.
I have no intention of trying to restore or replace these cells, especially as
they aren't interconnected in the way you'd expect.
The question remains... As nicads and NiMH cells are charged by constant
current (theoretically, anyway), what would cause the total post-charge
voltage to hit nearly eight volts?
John Robertson
Jan 11, 2014, 7:53:15 PM1/11/14
to
http://batteryuniversity.com/learn/article/charging_nickel_based_batteries
I've used this site for years when I want to figure out something
battery related...
John :-#)#
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(Please post followups or tech inquiries to the newsgroup)
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(604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."
William Sommerwerck
Jan 12, 2014, 8:27:43 AM1/12/14
to
"John Robertson" wrote in message
news:LuKdnU3ILK7hekzP...@giganews.com...
> I'm no expert, but why not ask your question here:
http://batteryuniversity.com/learn/article/charging_nickel_based_batteries
Why not? Thanks.
news:LuKdnU3ILK7hekzP...@giganews.com...
> I'm no expert, but why not ask your question here:
http://batteryuniversity.com/learn/article/charging_nickel_based_batteries
Why not? Thanks.
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