I've never had problems with the supposed rapid self-discharge of NiMH
cells. And now I have proof.

Almost two years ago, I visited a friend in Gold Bar WA for Christmas. I
took some camera equipment, including freshly charged NiMH cells for the
flash. I didn't take any flash pictures, so the cells remained unused in the
camera case -- which I just got around to unpacking yesterday. (Really.)

Four of the cells were 2700mAh Sanyo AAs. They all measured about 1.23V,
rather lower than the 1.4V NiMH cells commonly charge up to, but close to
the "nominal" 1.25V of NiMH and nicad cells. Contrary to Urban Legend, they
were not completely discharged.

I put them in a Canon 580EX II, and the flash fully charged up in less than
two seconds. I fired off some shots. The first few recycled "instantly". The
last two took about a half a second. I didn't run down the cells, but it was
obvious that two years of sitting on the shelf had no rendered them
unusable.

The belief that NiMH cells rapidly self-discharge is utter malarkey. Where
it came from, I don't know.

--
"We already know the answers -- we just haven't asked the right
questions." -- Edwin Land

On Dec 12, 4:26*am, "William Sommerwerck"
wrote:

The belief that NiMH cells rapidly self-discharge is utter malarkey. Where
it came from, I don't know.

My phone, my wife's phone, my Dremel nail grinder, and the eight Sony
AAs I bought before I knew about NiMHs, for a starter. These all are
replacements for or successors to products with NiCads, which by
comparison held a charge until needed.

"spamtrap1888" wrote in message
...
On Dec 12, 4:26 am, "William Sommerwerck"
wrote:

The belief that NiMH cells rapidly self-discharge is utter malarkey.
Where
it came from, I don't know.

My phone, my wife's phone, my Dremel nail grinder, and the eight Sony
AAs I bought before I knew about NiMHs, for a starter. These all are
replacements for or successors to products with NiCads, which by
comparison held a charge until needed.

Then why can four NiMH cells sit for two years and still be able to properly
power a high-drain device?

William Sommerwerck wrote:
I've never had problems with the supposed rapid self-discharge of NiMH
cells. And now I have proof.

Almost two years ago, I visited a friend in Gold Bar WA for Christmas. I
took some camera equipment, including freshly charged NiMH cells for the
flash. I didn't take any flash pictures, so the cells remained unused in the
camera case -- which I just got around to unpacking yesterday. (Really.)

Four of the cells were 2700mAh Sanyo AAs. They all measured about 1.23V,
rather lower than the 1.4V NiMH cells commonly charge up to, but close to
the "nominal" 1.25V of NiMH and nicad cells. Contrary to Urban Legend, they
were not completely discharged.

I put them in a Canon 580EX II, and the flash fully charged up in less than
two seconds. I fired off some shots. The first few recycled "instantly". The
last two took about a half a second. I didn't run down the cells, but it was
obvious that two years of sitting on the shelf had no rendered them
unusable.

The belief that NiMH cells rapidly self-discharge is utter malarkey. Where
it came from, I don't know.

so you got dead battery performance and maybe 3 flashes and therefor
batteries don't self discharge?

In article ,
William Sommerwerck wrote:

The belief that NiMH cells rapidly self-discharge is utter malarkey.
Where it came from, I don't know.

You seem to be drawing a sweeping conclusion based on one data point.
Not always a reliable approach?

Then why can four NiMH cells sit for two years and still be able to properly
power a high-drain device?

Likely possibility: the NiMH cells that you installed two years ago
use an internel chemistry which is superior to that used in
early-generation NiMH cells.

I definitely did observe the "rapid self-discharge" problem in the
first lots of NiMH cells I purchased and used, some years ago. They
simply were not reliable for storage times of more than 2-3 months...
they'd be down to less than half of their rated capacity after that
time.

Newer ones are much better. The ones advertised as "low self
discharge rate" (e.g Immedions, Eneloops, and the like) have been
available for several years, and I believe that the improved
low-self-discharge technologies have begun appearing in more
"mainstream" NiMH cells which aren't specifically advertised in this
way.

As I understand it, there's a tradeoff in NiMH cell chemistry:
capacity vs. self-discharge. Different metal alloys and structures
materials have different hydrogen-bonding characteristics... put
crudely, a tightly-binding structure will hold less total hydrogen
(i.e. less total charge storage capacity) but self-discharges at a
lower rate and thus holds its capacity for a longer time. Cells with
higher storage capacity use an alloy/structure which packs in more
hydrogen, but doesn't bind it as strongly and thus tends to
self-discharge more easily. [Again, this is a crude explanation based
on my own in-expert knowledge of the chemistry]

In good-quality NiMH AA cells currently on the market, cells down in
the 2000-2100 mAh range seem to be representative of the "lower
self-discharge rate" variety, and have a useful standby lifetime not
terribly different from NiCd cells. NiMH cells up in the 2400-2500 mAh
range seem to suffer more self-discharge. At least, that's my own
experience over the past year or two.

So, my guess is that the batteries you bought two years ago, were ones
at the lower-self-discharge end of the design range (even if not
explicitly advertised as such).

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

"Cydrome Leader" wrote in message
...
William Sommerwerck wrote:

I've never had problems with the supposed rapid self-discharge of NiMH
cells. And now I have proof.

Almost two years ago, I visited a friend in Gold Bar WA for Christmas. I
took some camera equipment, including freshly charged NiMH cells for the
flash. I didn't take any flash pictures, so the cells remained unused in
the
camera case -- which I just got around to unpacking yesterday. (Really.)

Four of the cells were 2700mAh Sanyo AAs. They all measured about 1.23V,
rather lower than the 1.4V NiMH cells commonly charge up to, but close to
the "nominal" 1.25V of NiMH and nicad cells. Contrary to Urban Legend,
they
were not completely discharged.

I put them in a Canon 580EX II, and the flash fully charged up in less
than
two seconds. I fired off some shots. The first few recycled "instantly".
The
last two took about a half second. I didn't run down the cells, but it
was
obvious that two years of sitting on the shelf had not rendered them
unusable.

The belief that NiMH cells rapidly self-discharge is utter malarkey.
Where
it came from, I don't know.

So you got dead battery performance and maybe 3 flashes and therefore
batteries don't self discharge?

Where did I say ANY SUCH THING?

I'm going to jump down your throat on this one, because I find most people
don't understand plain English. If I say "Some people have trouble getting
along with their bosses", most readers interpret that as "All people have
trouble getting along with their bosses." Really.

The cells WERE NOT DEAD. After two years they were at the nominal voltage
for a nicad or NiMH cell. Furthermore, they operated the flash without any
difficulty.

"Dave Platt" wrote in message
...
In article ,
William Sommerwerck wrote:

The belief that NiMH cells rapidly self-discharge is utter malarkey.
Where it came from, I don't know.

You seem to be drawing a sweeping conclusion based on one data point.
Not always a reliable approach?

It's not the only data point. I've never seen any NiMH cell "rapidly"
self-discharge. At least, not over a period of a month or two, which is the
general claim.

Furthermore, the claim is that ALL NiMH cells "rapidly" self-discharge. I've
seen both MAHA and (now) Sanyo cells hold their charge.


Then why can four NiMH cells sit for two years and still be able to
properly
power a high-drain device?

Likely possibility: the NiMH cells that you installed two years ago
use an internel chemistry which is superior to that used in
early-generation NiMH cells.

Unlikely. These are not low-discharge-rate cells.


Newer ones are much better. The ones advertised as "low self
discharge rate" (e.g Immedions, Eneloops, and the like) have been
available for several years, and I believe that the improved
low-self-discharge technologies have begun appearing in more
"mainstream" NiMH cells which aren't specifically advertised in this
way.

These cells are about three years old. And they're high-capacity -- 2700mAh.
To the best of my knowledgte, low-discharge cells have a lower capacity. I
think.


PS: I will not gainsay anyone's claim to have seen rapid NiMH
self-discharge. It's just that I haven't seen it. And I've been using NiMH
cells for almost five years.

In article ,
William Sommerwerck wrote:

The cells WERE NOT DEAD. After two years they were at the nominal voltage
for a nicad or NiMH cell. Furthermore, they operated the flash without any
difficulty.

To truly know whether (or how much) the cells had self-discharged,
you'd need to actually run them down to exhaustion and see how much
useful charge had been retained.

NiMH cells, like NiCd cells, have a rather flat discharge curve. Their
terminal voltage, and their ability to deliver current on demand,
don't change very much as they discharge... until they get down to
somewhere around the 10% charge level, at which point they "fall off
of a cliff" quite rapidly. They tend to work perfectly well, until
they die.

So, the fact that your batteries had a nominal terminal voltage, and
were able to charge the flash quickly and take a few photos, is useful
information, but by no means complete enough to diagnose whether (or
how much) the cells had discharged during storage.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

William Sommerwerck wrote:
"Cydrome Leader" wrote in message
...
William Sommerwerck wrote:

I've never had problems with the supposed rapid self-discharge of NiMH
cells. And now I have proof.

Almost two years ago, I visited a friend in Gold Bar WA for Christmas. I
took some camera equipment, including freshly charged NiMH cells for the
flash. I didn't take any flash pictures, so the cells remained unused in
the
camera case -- which I just got around to unpacking yesterday. (Really.)

Four of the cells were 2700mAh Sanyo AAs. They all measured about 1.23V,
rather lower than the 1.4V NiMH cells commonly charge up to, but close to
the "nominal" 1.25V of NiMH and nicad cells. Contrary to Urban Legend,
they
were not completely discharged.

I put them in a Canon 580EX II, and the flash fully charged up in less
than
two seconds. I fired off some shots. The first few recycled "instantly".
The
last two took about a half second. I didn't run down the cells, but it
was
obvious that two years of sitting on the shelf had not rendered them
unusable.

The belief that NiMH cells rapidly self-discharge is utter malarkey.
Where
it came from, I don't know.

So you got dead battery performance and maybe 3 flashes and therefore
batteries don't self discharge?

Where did I say ANY SUCH THING?

I'm going to jump down your throat on this one, because I find most people
don't understand plain English. If I say "Some people have trouble getting
along with their bosses", most readers interpret that as "All people have
trouble getting along with their bosses." Really.

The cells WERE NOT DEAD. After two years they were at the nominal voltage
for a nicad or NiMH cell. Furthermore, they operated the flash without any
difficulty.


Your test was unscientific, undocumented, anecdotal, incomplete.
You are certainly entitled to draw any conclusions you wish
and base your personal decisions on those conclusions.

Your blanket statement about NiMH based on your sample-of-one
anecdote requires extrapolation beyond reason. "Proof" is not
a word I'd have used to describe your result.

I can say that my personal experience differs from yours.
And I get along just fine with my boss. Really!!

William Sommerwerck wrote:
"Cydrome Leader" wrote in message
...
William Sommerwerck wrote:

I've never had problems with the supposed rapid self-discharge of NiMH
cells. And now I have proof.

Almost two years ago, I visited a friend in Gold Bar WA for Christmas. I
took some camera equipment, including freshly charged NiMH cells for the
flash. I didn't take any flash pictures, so the cells remained unused in
the
camera case -- which I just got around to unpacking yesterday. (Really.)

Four of the cells were 2700mAh Sanyo AAs. They all measured about 1.23V,
rather lower than the 1.4V NiMH cells commonly charge up to, but close to
the "nominal" 1.25V of NiMH and nicad cells. Contrary to Urban Legend,
they
were not completely discharged.

I put them in a Canon 580EX II, and the flash fully charged up in less
than
two seconds. I fired off some shots. The first few recycled "instantly".
The
last two took about a half second. I didn't run down the cells, but it
was
obvious that two years of sitting on the shelf had not rendered them
unusable.

The belief that NiMH cells rapidly self-discharge is utter malarkey.
Where
it came from, I don't know.

So you got dead battery performance and maybe 3 flashes and therefore
batteries don't self discharge?

Where did I say ANY SUCH THING?

sorry you got 100 full power flashes before the batteries died.

I'm going to jump down your throat on this one, because I find most people
don't understand plain English. If I say "Some people have trouble getting
along with their bosses", most readers interpret that as "All people have
trouble getting along with their bosses." Really.

people that talk about jumping down throats really need to shut the ****
up and not be talking about how to get along with a boss. Really.

The cells WERE NOT DEAD. After two years they were at the nominal voltage
for a nicad or NiMH cell. Furthermore, they operated the flash without any

There's nothing quite like the no load battery test.

difficulty.

yeah, for 3 flashes until the flash was unable to even recycle anymore.

"William Sommerwerck" wrote in message
...
"Dave Platt" wrote in message
...
In article ,
William Sommerwerck wrote:

The belief that NiMH cells rapidly self-discharge is utter malarkey.
Where it came from, I don't know.

You seem to be drawing a sweeping conclusion based on one data point.
Not always a reliable approach?

It's not the only data point. I've never seen any NiMH cell "rapidly"
self-discharge. At least, not over a period of a month or two, which is
the
general claim.

The local outlet of the Lidl store chain sometimes has NiMh cells at a very
tempting price so I bought loads - unfortunately they're no good for the
majority of occasional use items or clocks because they need tediously
frequent recharging.

As someone else pointed out there are advanced chemistry types - but more
expensive and harder to find.

"Ian Field" wrote in
:


"William Sommerwerck" wrote in message
...
"Dave Platt" wrote in message
...
In article ,
William Sommerwerck wrote:

The belief that NiMH cells rapidly self-discharge is utter
malarkey. Where it came from, I don't know.

You seem to be drawing a sweeping conclusion based on one data
point. Not always a reliable approach?

It's not the only data point. I've never seen any NiMH cell "rapidly"
self-discharge. At least, not over a period of a month or two, which
is the
general claim.

The local outlet of the Lidl store chain sometimes has NiMh cells at a
very tempting price so I bought loads - unfortunately they're no good
for the majority of occasional use items or clocks because they need
tediously frequent recharging.

As someone else pointed out there are advanced chemistry types - but
more expensive and harder to find.




I bought a 4 pack of Eveready NiMH cells for my hommade 2 watt bicycle
headlight,it outputs 200 lumens for .65A draw,and I go a long time(months)
before having to recharge,unless I use the light heavily.Of course,my
design does not draw any current when OFF.

some items have a draw even when not in use.
like my low cost Polaroid digital camera.

"Pre-charged" NiMH cells have a lower self-discharge rate,but they don't
seem to be all that more expennsive than regular NiMH.
they are slightly lower in mAH capacity.(2100mAH vs 2300mAH)

I'd ask the OP how many flashes or shots he got from his stored NiMH cells
before they needed recharge.
seems to me that 1.2V is pretty much "discharged" for NiMH cells.
ISTR that 1.1V is the low limit.

--
Jim Yanik
jyanik
at
localnet
dot com

"Jim Yanik" wrote in message
4...

"Pre-charged" NiMH cells have a lower self-discharge rate,but they don't
seem to be all that more expennsive than regular NiMH.
they are slightly lower in mAH capacity.(2100mAH vs 2300mAH)

I'd ask the OP how many flashes or shots he got from his stored
NiMH cells before they needed recharge.
seems to me that 1.2V is pretty much "discharged" for NiMH cells.
ISTR that 1.1V is the low limit.

I didn't run down the flash. I will do so tonight or tomorrow.

1.25V is considered the nominal operating voltage of nicad or NiMH cells.
(The point another poster made about the relatively flat discharge was
well-taken.) The "discharged" point is, as it is for cells of most
chemistries, 1.0V.

"Cydrome Leader" wrote in message
...

yeah, for 3 flashes until the flash was unable to even recycle anymore.

You're determined to deliberately misread what I wrote, aren't you?

William Sommerwerck wrote:
"Cydrome Leader" wrote in message
...

yeah, for 3 flashes until the flash was unable to even recycle anymore.

You're determined to deliberately misread what I wrote, aren't you?

Go slam some doors or something, you might be better at that than testing batteries.

William Sommerwerck wrote:
"Jim Yanik" wrote in message
4...

"Pre-charged" NiMH cells have a lower self-discharge rate,but they don't
seem to be all that more expennsive than regular NiMH.
they are slightly lower in mAH capacity.(2100mAH vs 2300mAH)

I'd ask the OP how many flashes or shots he got from his stored
NiMH cells before they needed recharge.
seems to me that 1.2V is pretty much "discharged" for NiMH cells.
ISTR that 1.1V is the low limit.

I didn't run down the flash. I will do so tonight or tomorrow.

1.25V is considered the nominal operating voltage of nicad or NiMH cells.
(The point another poster made about the relatively flat discharge was
well-taken.) The "discharged" point is, as it is for cells of most
chemistries, 1.0V.


What was the load current for your voltage measurement?

On Mon, 12 Dec 2011 10:08:27 -0800, "William Sommerwerck"
wrote:

"Dave Platt" wrote in message
...
In article ,
William Sommerwerck wrote:

The belief that NiMH cells rapidly self-discharge is utter malarkey.
Where it came from, I don't know.

You seem to be drawing a sweeping conclusion based on one data point.
Not always a reliable approach?

It's not the only data point. I've never seen any NiMH cell "rapidly"
self-discharge. At least, not over a period of a month or two, which is the
general claim.

Furthermore, the claim is that ALL NiMH cells "rapidly" self-discharge. I've
seen both MAHA and (now) Sanyo cells hold their charge.


Then why can four NiMH cells sit for two years and still be able to
properly
power a high-drain device?

Likely possibility: the NiMH cells that you installed two years ago
use an internel chemistry which is superior to that used in
early-generation NiMH cells.

Unlikely. These are not low-discharge-rate cells.


Newer ones are much better. The ones advertised as "low self
discharge rate" (e.g Immedions, Eneloops, and the like) have been
available for several years, and I believe that the improved
low-self-discharge technologies have begun appearing in more
"mainstream" NiMH cells which aren't specifically advertised in this
way.

These cells are about three years old. And they're high-capacity -- 2700mAh.
To the best of my knowledgte, low-discharge cells have a lower capacity. I
think.


PS: I will not gainsay anyone's claim to have seen rapid NiMH
self-discharge. It's just that I haven't seen it. And I've been using NiMH
cells for almost five years.

Shall I send you some glorious AA examples that never held enough
charge to operate a Canon Powershot A200 a week after a full charge?
I have them in both Duracell and no-name.

And no, it's *not* due to any shortcomings in the charger or camera.
Another brand of cells now delivers, months after charge.

On Mon, 12 Dec 2011 04:26:03 -0800, "William Sommerwerck"
wrote:

Four of the cells were 2700mAh Sanyo AAs. They all measured about 1.23V,
rather lower than the 1.4V NiMH cells commonly charge up to, but close to
the "nominal" 1.25V of NiMH and nicad cells. Contrary to Urban Legend, they
were not completely discharged.

NiMH cells do NOT totally discharge themselves. They discharge to
about 50% of capacity (by self-discharge) and then just sit there.

For example, here are some curves I ran for an Energizer 2300ma-hr
cell:
http://802.11junk.com/jeffl/NiMH/Energizer-NiMH-2300.jpg
and for an Duracell 2050ma-hr cell:
http://802.11junk.com/jeffl/NiMH/Duracelll-NiMH-2050.jpg
There were brand new cells used to test the assertion that NiMH cells
need to be charge cycled a few times before they reach full capacity.
Basically, that's true.

Note the voltages (under 1C load). For the Energizer, it starts off
at 1.35v and starts to die at about 1.10v. If you put a load on your
Sanyo cells, I'm fairly sure your 1.23v no load voltage will drop to
something around 1.18v. In other words, your Sanyo batteries
self-discharged until they were almost dead, and stopped.

I recently had a similar experience to what you found. I have two old
Norelco rotary shavers. I received both with dead batteries and
replaced them with NiMH cells of dubious origin. I only charge them
when needed, except this time, when a dry squall dropped a few trees
through the power lines.
http://802.11junk.com/jeffl/pics/2011-12-03-Storm/
When I dug out the shavers, the LCD indicator showed a nearly full
charge (about 80%). However, when I tried to use it, both lasted less
than 60 seconds. My guess(tm) is that I hadn't charged it since last
winter (9 months).

That's fairly close to what you observed. There was sufficient
voltage for the LCD indicator to proclaim a nearly full charge, but
not enough stored energy to do much useful work.


--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558
# http://802.11junk.com
# http://www.LearnByDestroying.com AE6KS

On Mon, 12 Dec 2011 18:20:52 -0800, Jeff Liebermann
wrote:

For example, here are some curves I ran for an Energizer 2300ma-hr
cell:
http://802.11junk.com/jeffl/NiMH/Energizer-NiMH-2300.jpg
and for an Duracell 2050ma-hr cell:
http://802.11junk.com/jeffl/NiMH/Duracelll-NiMH-2050.jpg
There were brand new cells used to test the assertion that NiMH cells
need to be charge cycled a few times before they reach full capacity.
Basically, that's true.

Hmmm... I haven't done anything with the batteries I used for this
test since May 29, 2011. They've just been sitting on the shelf. I
recall recharging them after I was done with the test. I'll run the
same 1C discharge test again in a few days and see how much capacity
is left after 7 months. This should be interesting. 1C is a heavy
load, but does yield fast results.

Note: I don't have phone or DSL at my house at this time and have
dragged my home computah to my office. This test will need to wait
until AT&T puts fixes things. Patience.

--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558
# http://802.11junk.com
# http://www.LearnByDestroying.com AE6KS

"Jeff Liebermann" wrote in message
...
On Mon, 12 Dec 2011 18:20:52 -0800, Jeff Liebermann
wrote:

For example, here are some curves I ran for an Energizer 2300ma-hr
cell:
http://802.11junk.com/jeffl/NiMH/Energizer-NiMH-2300.jpg
and for an Duracell 2050ma-hr cell:
http://802.11junk.com/jeffl/NiMH/Duracelll-NiMH-2050.jpg
There were brand new cells used to test the assertion that NiMH cells
need to be charge cycled a few times before they reach full capacity.
Basically, that's true.

Hmmm... I haven't done anything with the batteries I used for this
test since May 29, 2011. They've just been sitting on the shelf. I
recall recharging them after I was done with the test. I'll run the
same 1C discharge test again in a few days and see how much capacity
is left after 7 months. This should be interesting. 1C is a heavy
load, but does yield fast results.

Thanks. That would be interesting.

"Jeff Liebermann" wrote in message
...

NiMH cells do NOT totally discharge themselves. They discharge to
about 50% of capacity (by self-discharge) and then just sit there.

Then what is the problem? A 50% loss of capacity is hardly disastrous.


For example, here are some curves I ran for an Energizer 2300ma-hr
cell:
http://802.11junk.com/jeffl/NiMH/Energizer-NiMH-2300.jpg
and for an Duracell 2050ma-hr cell:
http://802.11junk.com/jeffl/NiMH/Duracelll-NiMH-2050.jpg
There were brand new cells used to test the assertion that NiMH cells
need to be charge cycled a few times before they reach full capacity.
Basically, that's true.

Note the voltages (under 1C load). For the Energizer, it starts off
at 1.35v and starts to die at about 1.10v. If you put a load on your
Sanyo cells, I'm fairly sure your 1.23v no load voltage will drop to
something around 1.18v. In other words, your Sanyo batteries
self-discharged until they were almost dead, and stopped.

But they weren't "almost dead".

This morning, I did what I should have done before I posted. Over a period
of a half-hour, I fired the Canon 580EX II over 100 times AT FULL POWER. The
recycling time was 3 to 3.5 seconds (not unreasonable for full-power
recycling), and the final cell voltage was about 1.21V (before the cells had
time to recover).

100 full-power flashes is not "almost dead". Had I fired on automatic, at a
moderate aperture, not using full power, I could easily have gotten 200 or
300 flashes. And had I been willing to tolerate a 5-second recycle, I
probably could have gotten another 100 full-power flashes.


I recently had a similar experience to what you found. I have two old
Norelco rotary shavers. I received both with dead batteries and
replaced them with NiMH cells of dubious origin. I only charge them
when needed, except this time, when a dry squall dropped a few trees
through the power lines.
http://802.11junk.com/jeffl/pics/2011-12-03-Storm/
When I dug out the shavers, the LCD indicator showed a nearly full
charge (about 80%). However, when I tried to use it, both lasted less
than 60 seconds. My guess(tm) is that I hadn't charged it since last
winter (9 months).
That's fairly close to what you observed. There was sufficient
voltage for the LCD indicator to proclaim a nearly full charge, but
not enough stored energy to do much useful work.

That isn't what I observed this morning. The cells, which had sat for almost
two years since being fully charged, were perfectly usable for 100
full-power flashes. I probably have gotten another 100 flashes, but I didn't
want to take the chance of abusing the flash.

The cells are Sanyo Superlattice Alloy EVO, model HR-3U. They were not
shipped pre-charged, and as far as I can tell, they are not
slow-self-discharge ("eneloop") cells. The Sanyo USA site has no information
about them. However, they are available from Batteries America. (Thomas
Distributing doesn't list them.)

http://store.batteriesamerica.com/hr...hcapacity.aspx

"Jeff Liebermann" wrote in message
...
On Mon, 12 Dec 2011 04:26:03 -0800, "William Sommerwerck"
wrote:

Four of the cells were 2700mAh Sanyo AAs. They all measured about 1.23V,
rather lower than the 1.4V NiMH cells commonly charge up to, but close to
the "nominal" 1.25V of NiMH and nicad cells. Contrary to Urban Legend,
they
were not completely discharged.

NiMH cells do NOT totally discharge themselves. They discharge to
about 50% of capacity (by self-discharge) and then just sit there.

ISTR NiCd cells frequently became shorted if allowed to self discharge too
often, but I haven't noticed it with NiMh.

On Tue, 13 Dec 2011 05:13:46 -0800, "William Sommerwerck"
wrote:


The cells are Sanyo Superlattice Alloy EVO, model HR-3U. They were not
shipped pre-charged, and as far as I can tell, they are not
slow-self-discharge ("eneloop") cells. The Sanyo USA site has no information
about them. However, they are available from Batteries America. (Thomas
Distributing doesn't list them.)

http://www.houseofbatteries.com/documents/HR-3U-2500.pdf
No mention of low self-discharge.

100 flashes does seem like an almost fully charged battery. However,
with such an intermittent load, it would have been nice if you had a
more controlled and more measurable way to test charge level. If what
you say is true, then you may be correct that there's no
self-discharge for a *NEW* NiMH battery. I'm wondering if it might be
a phenomenon that appears later as the battery is used. I'll run my
little discharge test when I have time and get my computer back home.

Incidentally, several people have mentioned that you cannot use the
open circuit voltage as an indication of state of charge. I agree. It
works with batteries that have sloping discharge curves, such as
carbon-zinc and some alkaline. However, batteries that have a flat
discharge curve offer such a small change in terminal voltage, that
the numbers are difficult to distinguish from tolerance and
temperature variations. The only way that seems to work for such
batteries are coulomb counter chips, as found in many laptop
batteries.

More later... bizzeeeeeee
--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558
# http://802.11junk.com
# http://www.LearnByDestroying.com AE6KS

"Jeff Liebermann"

NiMH cells do NOT totally discharge themselves. They discharge to
about 50% of capacity (by self-discharge) and then just sit there.


** I have several sets of AA NiMH cells - all Sanyo brand and rated at 1700
to 2500 mAH.

Self discharge is a REAL problem, but no worse than with NiCds.

In general, charged cells lose 90% of capacity in about 6 to 8 weeks -
taking a full 6 hour charge at 400mA to recover.

In my Canon A430, the uncharged cells will run the back display for a few
minutes, let me take a few shots and maybe one flash before the camera shuts
down.


.... Phil

On Tue, 13 Dec 2011 05:13:46 -0800, "William Sommerwerck"
wrote:
The cells are Sanyo Superlattice Alloy EVO, model HR-3U. They were not
shipped pre-charged, and as far as I can tell, they are not
slow-self-discharge ("eneloop") cells. The Sanyo USA site has no information
about them. However, they are available from Batteries America. (Thomas
Distributing doesn't list them.)

This might be of interest:
http://www.stefanv.com/electronics/sanyo_eneloop.html
It's an independent test of the Sanyo Eneloop NiMH batteries including
some self-discharge tests. Unfortunately, he doesn't compare the
results with the non-LSD batteries. Scroll down to the "Self
Discharge" section heading and note the self-discharge tables.
50% charge loss after 1 year.

There is also this quote from Sanyo:
Storage temperature is of high importance if you measure
self-discharge rate. Higher temperatures substantially
increase self-discharging. It is best to store Eneloops
as cool as possible to keep the charge in the battery.
As a rule-of-thumb, every 10°C increase in storage
temperature is equivalent to doubling the storage time.
Some R/C pilots in Europe put Eneloops in the freezer,
with rather good results.
So, how were your batteries stored?

Presumably, the non-LSD batteries would produce much worse results,
making your miraculous Sanyo HR-3U cells better than Eneloop cells,
which seems rather dubious. Since the Eneloop batteries tested were
brand new, I don't think it's something related to an aging effect.
That leaves your test as an oddity. Are you sure someone didn't
charge your batteries when nobody was looking?



--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558
# http://802.11junk.com
# http://www.LearnByDestroying.com AE6KS

On Tue, 13 Dec 2011 19:45:07 -0800, Jeff Liebermann
wrote:

This might be of interest:
http://www.stefanv.com/electronics/sanyo_eneloop.html
It's an independent test of the Sanyo Eneloop NiMH batteries including
some self-discharge tests. Unfortunately, he doesn't compare the
results with the non-LSD batteries.

Ok, I lied[1]. There is a comparison. See:
http://www.stefanv.com/electronics/sanyo_eneloop.html#compare
The graph shows the Eneloop battery to be MUCH better at
self-discharge than the conventional NiMH. After 1 year, the Eneloop
retained about 50% of charge, while the conventional NiMH retained
only 2.6%.

[1] I'm suppose to be doing my end of year billing and bookkeeping. I
hate doing billing and am therefore easily diverted. If I go broke,
it's all your fault for creating an interesting diversion.

--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558
# http://802.11junk.com
# http://www.LearnByDestroying.com AE6KS

"Jeff Liebermann" wrote in message
...

100 flashes does seem like an almost fully charged battery.

But it isn't, of course. The voltage was at the nominal 1.25V when I
started, but this is well below the end-of-charge voltage for NiMH cells.


However, with such an intermittent load, it would have been nice if you
had a more controlled and more measurable way to test charge level.
If what you say is true, then you may be correct that there's no
self-discharge for a *NEW* NiMH battery. I'm wondering if it might be
a phenomenon that appears later as the battery is used. I'll run my
little discharge test when I have time and get my computer back home.

It was "scientific" in the sense of mimicking photographic use. 100+
full-power shots in a half hour, three at a time, is fairly extreme use.


Incidentally, several people mentioned that you cannot use the
open-circuit voltage as an indication of state of charge. I agree.

Of course. That's one of the problems with nicad and NiMH cells.

However, the fact that the cells read about 1.25V showed they WERE NOT fully
charged. But despite having sat for two years, they were able to give 100+
full-power shots. The point is that their were perfectly usable without
having to be recharged. This contradicts belief that NiMH cells rapidly
self-discharge. (Rates of 1% or more per day are stated.)

I might disable the flash's auto-shutoff and let the cells run down to 1.0V,
then see whether it can still fire more than once. (I have no desire to keep
popping the flash.)

PS: Sanyo says their current eneloop cells (rated at 1500 charge cycles)
will hold as much of 75% of their charge for 3 years.

"Phil Allison" wrote in message
...
"Jeff Liebermann"

NiMH cells do NOT totally discharge themselves. They discharge to
about 50% of capacity (by self-discharge) and then just sit there.

** I have several sets of AA NiMH cells - all Sanyo brand and rated at
1700
to 2500 mAH.

Self discharge is a REAL problem, but no worse than with NiCds.

In general, charged cells lose 90% of capacity in about 6 to 8 weeks -
taking a full 6 hour charge at 400mA to recover.

In my Canon A430, the uncharged cells will run the back display for a few
minutes, let me take a few shots and maybe one flash before the camera
shuts
down.

I wonder if the "spectacular" behavior of my 2700mAh Sanyos has anything to
do with their "superlattice alloy" construction. These appear to be the only
Sanyos using this design. (That's life, I guess.)

http://en.wikipedia.org/wiki/Superlattice

Anyone care to explain this article to me?

"Jeff Liebermann" wrote in message
...

There is also this quote from Sanyo:
Storage temperature is of high importance if you measure
self-discharge rate. Higher temperatures substantially
increase self-discharging. It is best to store Eneloops
as cool as possible to keep the charge in the battery.
As a rule-of-thumb, every 10°C increase in storage
temperature is equivalent to doubling the storage time.
Some R/C pilots in Europe put Eneloops in the freezer,
with rather good results.
So, how were your batteries stored?

This is the typical "doubling of chemical reactions with each increase of
10°C" rule.

Right before Christmas 2009, I packed up my camera bag for a visit to Gold
Bar, WA. Two packs of NiMH cells were in the bag. When I came home, I put
the bag on the living room floor, where it has remained for almost two
years. The Pacific Northwest is cooler than the rest of the country. The
cells were exposed to "high" temperatures only intermittently, during the
warmer days of Summer.


Presumably, the non-LSD...

Hmmm... Is there a purple owl on these cells?

...batteries would produce much worse results, making your
miraculous Sanyo HR-3U cells better than Eneloop cells,
which seems rather dubious.

Agreed, but we don't know whether the "superlattice alloy" has magical
powers.


Since the Eneloop batteries tested were
brand new, I don't think it's something related to an aging effect.
That leaves your test as an oddity. Are you sure someone didn't
charge your batteries when nobody was looking?

Well, it was around Christmas... Elves, perhaps? Brownies?

Speaking of which... One of Stan Freberg's less-well-known recordings is
"Yulenet", with Joe Friday trying to convince a doubter named Grudge that
there really is a Santa Claus. When they visit the North Pole, they're
greeted by a brownie from the South Pole (Daws Butler doing a silly
mock-Southern voice) who's helping out while Santa is away. I can imagine
the flap such a joke would cause today...

"Jeff Liebermann" wrote in message
...
On Tue, 13 Dec 2011 19:45:07 -0800, Jeff Liebermann
wrote:

This might be of interest:
http://www.stefanv.com/electronics/sanyo_eneloop.html
It's an independent test of the Sanyo Eneloop NiMH batteries including
some self-discharge tests. Unfortunately, he doesn't compare the
results with the non-LSD batteries.

Ok, I lied[1]. There is a comparison. See:
http://www.stefanv.com/electronics/sanyo_eneloop.html#compare
The graph shows the Eneloop battery to be MUCH better at
self-discharge than the conventional NiMH. After 1 year, the Eneloop
retained about 50% of charge, while the conventional NiMH retained
only 2.6%.

[1] I'm suppose to be doing my end of year billing and bookkeeping. I
hate doing billing and am therefore easily diverted. If I go broke,
it's all your fault for creating an interesting diversion.

Extremely interesting.

I'll contact Sanyo and ask them about the self-discharge of my specific
cells.

On Tue, 13 Dec 2011 19:45:07 -0800, Jeff Liebermann
wrote:

On Tue, 13 Dec 2011 05:13:46 -0800, "William Sommerwerck"
wrote:
The cells are Sanyo Superlattice Alloy EVO, model HR-3U. They were not
shipped pre-charged, and as far as I can tell, they are not
slow-self-discharge ("eneloop") cells. The Sanyo USA site has no information
about them. However, they are available from Batteries America. (Thomas
Distributing doesn't list them.)

This might be of interest:
http://www.stefanv.com/electronics/sanyo_eneloop.html
It's an independent test of the Sanyo Eneloop NiMH batteries including
some self-discharge tests. Unfortunately, he doesn't compare the
results with the non-LSD batteries. Scroll down to the "Self
Discharge" section heading and note the self-discharge tables.
50% charge loss after 1 year.

There is also this quote from Sanyo:
Storage temperature is of high importance if you measure
self-discharge rate. Higher temperatures substantially
increase self-discharging. It is best to store Eneloops
as cool as possible to keep the charge in the battery.
As a rule-of-thumb, every 10°C increase in storage
temperature is equivalent to doubling the storage time.
Some R/C pilots in Europe put Eneloops in the freezer,
with rather good results.
So, how were your batteries stored?

Presumably, the non-LSD batteries would produce much worse results,
making your miraculous Sanyo HR-3U cells better than Eneloop cells,
which seems rather dubious. Since the Eneloop batteries tested were
brand new, I don't think it's something related to an aging effect.
That leaves your test as an oddity. Are you sure someone didn't
charge your batteries when nobody was looking?

In for a penny's worth; i add that this might be some freaky low self
discharge cells for the given process, perhaps at some process corner for
the set.

?-)

I'll try to make this quick...

Canon's specs for the 580EX II flash appear to be based on nicad or NiMH
cells starting at 1.25 volts. As I explained, when the unloaded voltage was
at 1.21V, I had no trouble getting more than 100 full-power flashes, which
meets the 100 - 700 flash spec in the book. After letting the flash sit,
running, for several hours, the unloaded voltage was about 1.18V. After
removing and replacing the cells, the flash charged up once, taking more
than 7 seconds. After firing it, it would not recycle.

Several points... The cells had sat for two years, but delivered at least
the spec'd number of flashes. Some NiMH cells might self-discharge quickly,
but these Sanyos did not. (I was surprised that, throughout the discharge,
the cells' voltages were virtually identical, never differing by more than
about 10mV. This suggests very tight manufacturing tolerances.)

It was also interesting that the flash "conked out" well before the cells
reached 1.0V. This suggests that this flash is /not/ designed to work down
to 1V per cell, the traditional "standard" of battery-operated designs.

"William Sommer******"

Canon's specs for the 580EX II flash appear to be based on nicad or NiMH
cells starting at 1.25 volts.

** The manual clearly states that it is based on Alkaline cells.

This implies that the unit will operate with much lower cell voltages and
currents than modern digital cameras require.


As I explained, when the unloaded voltage was
at 1.21V,


** It is totally meaningless to quote unloaded voltages of MiNH, NiCd or
alkaline cells.

Only when loaded as in the application does terminal voltage become
meaningful.



.... Phil

On Fri, 16 Dec 2011 05:11:33 -0800, "William Sommerwerck"
wrote:

I'll try to make this quick...

Canon's specs for the 580EX II flash appear to be based on nicad or NiMH
cells starting at 1.25 volts. As I explained, when the unloaded voltage was
at 1.21V, I had no trouble getting more than 100 full-power flashes, which
meets the 100 - 700 flash spec in the book. After letting the flash sit,
running, for several hours, the unloaded voltage was about 1.18V. After
removing and replacing the cells, the flash charged up once, taking more
than 7 seconds. After firing it, it would not recycle.

Several points... The cells had sat for two years, but delivered at least
the spec'd number of flashes.

" at least the MINIMUM spec'd number of flashes" - which you would
expect given (a) the expanse of the range specified (100-700) and (b)
the proximity of your cells' voltage to the Canon staring point.

Some NiMH cells might self-discharge quickly,
but these Sanyos did not. (I was surprised that, throughout the discharge,
the cells' voltages were virtually identical, never differing by more than
about 10mV. This suggests very tight manufacturing tolerances.)

Sanyo is probably the most highly regarded name in both NiCd and NiMH
manufacture. You shouldn't be surprised.

It was also interesting that the flash "conked out" well before the cells
reached 1.0V. This suggests that this flash is /not/ designed to work down
to 1V per cell, the traditional "standard" of battery-operated designs.

Several points... The cells had sat for two years, but delivered at least
the spec'd number of flashes.

" at least the MINIMUM spec'd number of flashes" - which you would
expect given (a) the expanse of the range specified (100-700) and (b)
the proximity of your cells' voltage to the Canon staring point.

100 is for a full-power flash. The 700 refers to a partial-power flash,
under auto-exposure.

"William Sommer****** is Full of **** "


100 is for a full-power flash.


** The flash energy input is probably about 20 Joules, ie 330uF and 350V.

Allowing 5 Joules for losses, the energy required for 100 flashes is 2500
Joules.

A fully charged, 2500mAH NiMH has a capacity of 11,000 Joules ( 1.2 x 2.5 x
3600 )

Four of them have a capacity of 44,000 Joules

So, your "magic" Sanyo cells had under 6% of normal capacity.



.... Phil

who where wrote:
On Fri, 16 Dec 2011 05:11:33 -0800, "William Sommerwerck"
wrote:

I'll try to make this quick...

Canon's specs for the 580EX II flash appear to be based on nicad or NiMH
cells starting at 1.25 volts. As I explained, when the unloaded voltage was
at 1.21V, I had no trouble getting more than 100 full-power flashes, which
meets the 100 - 700 flash spec in the book. After letting the flash sit,
running, for several hours, the unloaded voltage was about 1.18V. After
removing and replacing the cells, the flash charged up once, taking more
than 7 seconds. After firing it, it would not recycle.

Several points... The cells had sat for two years, but delivered at least
the spec'd number of flashes.

" at least the MINIMUM spec'd number of flashes" - which you would
expect given (a) the expanse of the range specified (100-700) and (b)
the proximity of your cells' voltage to the Canon staring point.

Some NiMH cells might self-discharge quickly,
but these Sanyos did not. (I was surprised that, throughout the discharge,
the cells' voltages were virtually identical, never differing by more than
about 10mV. This suggests very tight manufacturing tolerances.)

Sanyo is probably the most highly regarded name in both NiCd and NiMH
manufacture. You shouldn't be surprised.

It was also interesting that the flash "conked out" well before the cells
reached 1.0V. This suggests that this flash is /not/ designed to work down
to 1V per cell, the traditional "standard" of battery-operated designs.

Make sure you're comparing apples with apples.
The unloaded voltage of a cell is irrelevant.
I've found it very difficult to get the unloaded voltage of NiMH below
1.2V. Discharge it down to .8V, remove the load and let it sit and
it will creep back up to 1.2V. But it's still dead and can't supply
much current.
A flash is a VERY high current device. Once the LOADED voltage gets
much below 1V, it's too weak for a flash. The ONLY useful voltage
measurement is with the intended load.

A useful measurement is internal resistance. Use a square-wave load from
1/2A to 1A. Measure the P-P amplitude of the cell voltage and use that
to calculate a resistance dV/dI. Try it at different states of charge.

Calculate the voltage drop from your load current and the ISR.
Multiply that by the number of series cells and it's easy to see
why high-current loads quit working long before the open-circuit
voltage gets below 1.2V.

"Phil Allison" wrote in message
...

"William Sommer****** is Full of **** "

Phil Allison is a foul-mouthed shmuck.

By the way, in German "shmuck" means "jewelry" or "adornment". Billy Wilder
gets a funny gag out of this in "One, Two, Three".


100 is for a full-power flash.

The flash energy input is probably about 20 joules, ie 330uF
and 350V. Allowing 5 joules for losses, the energy required for
100 flashes is 2500 joules.

The losses are probably greater than that. When I left the flash running,
without firing it, I was surprised that it conked out after about two hours.

I suspect this flash provides more than 20Ws output. But the specs are
silent on this.


A fully charged, 2500mAH NiMH has a capacity of 11,000 joules
(1.2 x 2.5 x 3600). Four of them have a capacity of 44,000 joules.
So, your "magic" Sanyo cells had under 6% of normal capacity.

I can't argue with plausibly-chosen numbers, and I won't. However...

You're still missing the point. We have been told that NiMH cells lose
several percent of their capacity every week. (Let's say 3%, and assume it's
a linear loss, rather than exponential.) After 102 weeks, the cells should
have been dead, dead, dead. They were not. They had no trouble powering the
flash to its spec'd number of full-power flashes. What do you want, for
heaven's sake?

The point about "voltage creep" of nicads & NiMH cells was well-taken.
However, I measured the cells' voltages within about 15 seconds of shutting
off the flash. Furthermore, the under-load voltage is arguably not that
important if the DUT works as it's spec'd. Which this flash did.

Please note that I actually performed an experiment! I tested cells that
should have been useless. They were not. The statement that conventional
NiMH cells are generically incapable of holding a charge for extended
periods is simply NOT TRUE. Not because "I say so", but because I have
empirical evidence.

Yesterday I pulled out my Sunpak 622 Super, a "professional" potato-masher
flash. It has four 5500mAh NiMH C cells made by CTA, whoever that is. (They
came from Overstock.) The last time I charged them was about six months ago.
I flicked the power switch, and unit came to full power in 6 seconds.
Full-power recycling was 4 seconds -- not great, but not bad, either,
especially for "dead" cells..

"mike" wrote in message
...

Make sure you're comparing apples with apples.
The unloaded voltage of a cell is irrelevant.
I've found it very difficult to get the unloaded voltage of NiMH below
1.2V. Discharge it down to .8V, remove the load and let it sit and
it will creep back up to 1.2V. But it's still dead and can't supply
much current.
A flash is a VERY high current device. Once the LOADED voltage gets
much below 1V, it's too weak for a flash. The ONLY useful voltage
measurement is with the intended load.

A useful measurement is internal resistance. Use a square-wave load from
1/2A to 1A. Measure the P-P amplitude of the cell voltage and use that
to calculate a resistance dV/dI. Try it at different states of charge.

Calculate the voltage drop from your load current and the ISR.
Multiply that by the number of series cells and it's easy to see
why high-current loads quit working long before the open-circuit
voltage gets below 1.2V.

I shouldn't have said anything about the voltage.

The point is that the cells "should" have been dead, but weren't. After
nearly two years, they powered the flash to its spec's number of flashes.