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William Sommerwerck
Guest
Mon Dec 12, 2011 1:26 pm
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
William Sommerwerck
Guest
Mon Dec 12, 2011 4:47 pm
"spamtrap1888" <spamtrap1888_at_gmail.com> wrote in message
news:52a89893-486e-4517-9b48-79dd505e07e0_at_f36g2000prj.googlegroups.com...
On Dec 12, 4:26 am, "William Sommerwerck" <grizzledgee...@comcast.net>
wrote:
Quote:
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?
spamtrap1888
Guest
Mon Dec 12, 2011 5:36 pm
On Dec 12, 4:26 am, "William Sommerwerck" <grizzledgee...@comcast.net>
wrote:
Quote:
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.
Dave Platt
Guest
Mon Dec 12, 2011 6:34 pm
In article <jc57nd$dlp$1_at_dont-email.me>,
William Sommerwerck <grizzledgeezer_at_comcast.net> wrote:
Quote:
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?
Quote:
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 <dplatt_at_radagast.org> 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
Guest
Mon Dec 12, 2011 6:49 pm
William Sommerwerck <grizzledgeezer_at_comcast.net> wrote:
Quote:
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?
William Sommerwerck
Guest
Mon Dec 12, 2011 7:02 pm
"Cydrome Leader" <presence_at_MUNGEpanix.com> wrote in message
news:jc5bal$9ic$2_at_reader1.panix.com...
Quote:
William Sommerwerck <grizzledgeezer_at_comcast.net> wrote:
I've never had problems with the supposed rapid self-discharge of NiMH
cells. And now I have proof.
Almost two years ago, I visited a friend in Gold Bar WA for Christmas. I
took some camera equipment, including freshly charged NiMH cells for the
flash. I didn't take any flash pictures, so the cells remained unused in
the
camera case -- which I just got around to unpacking yesterday. (Really.)
Four of the cells were 2700mAh Sanyo AAs. They all measured about 1.23V,
rather lower than the 1.4V NiMH cells commonly charge up to, but close to
the "nominal" 1.25V of NiMH and nicad cells. Contrary to Urban Legend,
they
were not completely discharged.
I put them in a Canon 580EX II, and the flash fully charged up in less
than
two seconds. I fired off some shots. The first few recycled "instantly".
The
last two took about a half second. I didn't run down the cells, but it
was
obvious that two years of sitting on the shelf had not rendered them
unusable.
The belief that NiMH cells rapidly self-discharge is utter malarkey.
Where
it came from, I don't know.
So you got dead battery performance and maybe 3 flashes and therefore
batteries don't self discharge?
Where did I say ANY SUCH THING?
I'm going to jump down your throat on this one, because I find most people
don't understand plain English. If I say "Some people have trouble getting
along with their bosses", most readers interpret that as "All people have
trouble getting along with their bosses." Really.
The cells WERE NOT DEAD. After two years they were at the nominal voltage
for a nicad or NiMH cell. Furthermore, they operated the flash without any
difficulty.
William Sommerwerck
Guest
Mon Dec 12, 2011 7:08 pm
"Dave Platt" <dplatt_at_radagast.org> wrote in message
news:lhqhr8-5o7.ln1_at_radagast.org...
Quote:
In article <jc57nd$dlp$1_at_dont-email.me>,
William Sommerwerck <grizzledgeezer_at_comcast.net> 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.
Quote:
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.
Quote:
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.
Dave Platt
Guest
Mon Dec 12, 2011 7:26 pm
In article <jc5fkq$3f7$1_at_dont-email.me>,
William Sommerwerck <grizzledgeezer_at_comcast.net> wrote:
Quote:
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 <dplatt_at_radagast.org> 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!
mike
Guest
Mon Dec 12, 2011 7:31 pm
William Sommerwerck wrote:
Quote:
"Cydrome Leader" <presence_at_MUNGEpanix.com> wrote in message
news:jc5bal$9ic$2_at_reader1.panix.com...
William Sommerwerck <grizzledgeezer_at_comcast.net> 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!!
Ian Field
Guest
Mon Dec 12, 2011 10:32 pm
"William Sommerwerck" <grizzledgeezer_at_comcast.net> wrote in message
news:jc5fvm$5p7$1_at_dont-email.me...
Quote:
"Dave Platt" <dplatt_at_radagast.org> wrote in message
news:lhqhr8-5o7.ln1_at_radagast.org...
In article <jc57nd$dlp$1_at_dont-email.me>,
William Sommerwerck <grizzledgeezer_at_comcast.net> 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.
Cydrome Leader
Guest
Mon Dec 12, 2011 10:39 pm
William Sommerwerck <grizzledgeezer_at_comcast.net> wrote:
Quote:
"Cydrome Leader" <presence_at_MUNGEpanix.com> wrote in message
news:jc5bal$9ic$2_at_reader1.panix.com...
William Sommerwerck <grizzledgeezer_at_comcast.net> 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.
Quote:
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 fuck
up and not be talking about how to get along with a boss. Really.
Quote:
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.
Quote:
difficulty.
yeah, for 3 flashes until the flash was unable to even recycle anymore.
Jim Yanik
Guest
Mon Dec 12, 2011 10:51 pm
"Ian Field" <gangprobing.alien_at_ntlworld.com> wrote in
news:hquFq.145226$GZ1.136984_at_newsfe02.ams2:
Quote:
"William Sommerwerck" <grizzledgeezer_at_comcast.net> wrote in message
news:jc5fvm$5p7$1_at_dont-email.me...
"Dave Platt" <dplatt_at_radagast.org> wrote in message
news:lhqhr8-5o7.ln1_at_radagast.org...
In article <jc57nd$dlp$1_at_dont-email.me>,
William Sommerwerck <grizzledgeezer_at_comcast.net> 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
William Sommerwerck
Guest
Mon Dec 12, 2011 11:34 pm
"Jim Yanik" <jyanik_at_abuse.gov> wrote in message
news:Xns9FB9ABAE3C1EAjyaniklocalnetcom_at_216.168.3.44...
Quote:
"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.
William Sommerwerck
Guest
Mon Dec 12, 2011 11:35 pm
"Cydrome Leader" <presence_at_MUNGEpanix.com> wrote in message
news:jc5opq$7k7$1_at_reader1.panix.com...
Quote:
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?
mike
Guest
Tue Dec 13, 2011 12:39 am
William Sommerwerck wrote:
Quote:
"Jim Yanik" <jyanik_at_abuse.gov> wrote in message
news:Xns9FB9ABAE3C1EAjyaniklocalnetcom_at_216.168.3.44...
"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?
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