NiMH new battery conditioning

[Jeff Liebermann]

Per a previous discussion, I decided to test whether new NiMH
batteries need to be conditioned or charged several times before
reaching their rated capacity. Apparently they do.

The test setup is a West Mtn Radio CBA-IIv1 battery analyzer.
<http://802.11junk.com/jeffl/NiMH/cba-II.jpg>
I didn't want to wait 20 hrs per test to get the official rated
capacity, so I elected to run the tests at 1C which resulted in about
a 45 minute test, but also resulted in a much lower capacity result.
It also caused some unexpected errors. The design of the CBA-II does
not include a Kelvin probe connection to eliminate any losses in the
cables and connectors. It measures the voltage at the load, instead
of at the battery. This is not a problem at low load currents, but at
2 amps, results in considerable error.

Two new (out of the package) batteries were used. An Energizer NiMH
2300 ma-hr cell, and a Duracell 2050 ma-hr cell. Between tests, the
batteries were quick charged in a Radio Shack 23-1305 NiMH quick
charger (15 min). Each battery was discharged 3 times and the
discharge curves plotted.

Note that the Energizer package says 2450 ma-hr, while the battery is
marked 2300 ma-hrs.
<http://802.11junk.com/jeffl/NiMH/energizer.jpg>

The Energizer cell showed no change in capacity between discharges.
<http://802.11junk.com/jeffl/NiMH/Energizer-NiMH-2300.jpg>
Using 1.0VDC as the end point, the measured cell capacity is:
Run 1 1785 ma-hr
Run 2 1890 ma-hr
Run 3 1895 ma-hr

The Duracell cell showed a larger change.
<http://802.11junk.com/jeffl/NiMH/Duracelll-NiMH-2050.jpg>
Using 1.0VDC as the end point, the measured cell capacity is:
Run 1 1200 ma-hr
Run 2 1270 ma-hr
Run 3 1385 ma-hr

The net improvement over 3 charge-discharge runs is about 10% for the
Energizer and 15% for the Duracell. Not huge, but certainly
measurable. Whether it is worth the effort conditioning the battery
before use, is debatable.

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

 

[Phil Allison]

"Jeff Liebermann"

Per a previous discussion, I decided to test whether new NiMH
batteries need to be conditioned or charged several times before
reaching their rated capacity. Apparently they do.

The test setup is a West Mtn Radio CBA-IIv1 battery analyzer.
http://802.11junk.com/jeffl/NiMH/cba-II.jpg
I didn't want to wait 20 hrs per test to get the official rated
capacity, so I elected to run the tests at 1C which resulted in about
a 45 minute test, but also resulted in a much lower capacity result.
It also caused some unexpected errors. The design of the CBA-II does
not include a Kelvin probe connection to eliminate any losses in the
cables and connectors. It measures the voltage at the load, instead
of at the battery. This is not a problem at low load currents, but at
2 amps, results in considerable error.

Two new (out of the package) batteries were used. An Energizer NiMH
2300 ma-hr cell, and a Duracell 2050 ma-hr cell. Between tests, the
batteries were quick charged in a Radio Shack 23-1305 NiMH quick
charger (15 min). Each battery was discharged 3 times and the
discharge curves plotted.

Note that the Energizer package says 2450 ma-hr, while the battery is
marked 2300 ma-hrs.
http://802.11junk.com/jeffl/NiMH/energizer.jpg

The Energizer cell showed no change in capacity between discharges.
http://802.11junk.com/jeffl/NiMH/Energizer-NiMH-2300.jpg
Using 1.0VDC as the end point, the measured cell capacity is:
Run 1 1785 ma-hr
Run 2 1890 ma-hr
Run 3 1895 ma-hr

The Duracell cell showed a larger change.
http://802.11junk.com/jeffl/NiMH/Duracelll-NiMH-2050.jpg
Using 1.0VDC as the end point, the measured cell capacity is:
Run 1 1200 ma-hr
Run 2 1270 ma-hr
Run 3 1385 ma-hr

The net improvement over 3 charge-discharge runs is about 10% for the
Energizer and 15% for the Duracell. Not huge, but certainly
measurable. Whether it is worth the effort conditioning the battery
before use, is debatable.

** You got something against NiMh cells ?

I would never mistreat NiMH AA cells the way you just have.

15 minute charging is absurd for any cell NOT designed for such abuse - it
causes overheating with new cells and destruction of older ones.

A 1C discharge test will never give the rated capacity figure with NiCd or
NiMH.

IME - the idea that new cells have a "running in "period is a MYTH
invented by retailers back in the 1970s when consumers were first sold AA
and C size NiCds and found their performance disappointing when compared to
alkalines.

The inherent lower terminal voltage and cell mAH capacity were the real
reasons.


..... Phil

 

[Jeff Liebermann]

On Tue, 31 May 2011 14:37:43 +1000, "Phil Allison" <phil_a@tpg.com.au>
wrote:

** You got something against NiMh cells ?

Yep. I don't like them.

I would never mistreat NiMH AA cells the way you just have.

I didn't have time to do it the right way (20 hr discharge). I can do
it again with a longer discharge time and lower current. I still have
several of both brand of cells that I haven't mistreated yet. However,
it will take about a week to produce results (plus dragging home a
spare computah to do the test and building a better battery holder).

15 minute charging is absurd for any cell NOT designed for such abuse - it
causes overheating with new cells and destruction of older ones.

True for the Duracell, which recommends 205ma for 15 hrs to recharge
printed on the cell. The Energizer Recharge battery doesn't specify a
charge current:
<http://data.energizer.com/PDFs/nh15-2000.pdf>
However, the recommended battery charger is a quick charger:
<http://data.energizer.com/PDFs/ch15mn2.pdf>
with a 15 minute charge time.

I've been testing batteries since about 2005 while working on a
product that I won't discuss. However, I will point out that many
NiCd batteries can be quick charged at ridiculously high rates, as
long as certain (unspecified) conditions are met. If you don't mind,
I'll leave this unsubstantiated.

Incidentally, the Sanyo ENELOOP battery data sheet recommends fast
charging at 2A for 1.1 hrs:
<http://www.eneloop.info/fileadmin/EDITORS/ENELOOP/DATA_SHEETS/HR-3UTGA_data_sheet.pdf>

A 1C discharge test will never give the rated capacity figure with NiCd or
NiMH.

I indicated that in my posting as:

I didn't want to wait 20 hrs per test to get the official rated
capacity, so I elected to run the tests at 1C which resulted in about
a 45 minute test, but also resulted in a much lower capacity result.

The purpose of the test was to see if a brand new battery required
several charge-discharge cycles before it would deliver full capacity,
not to measure the actual rated capacity in a 20 hr discharge test.

IME - the idea that new cells have a "running in "period is a MYTH
invented by retailers back in the 1970s when consumers were first sold AA
and C size NiCds and found their performance disappointing when compared to
alkalines.

Maybe. There was also quite a bit of effort in the mid 1990's by
manufactures to differentiate their NiMH products from NiCd. For
example, I found a pair of Lenmar NoMEM Pro NiMH batteries, which are
an obvious shot at the alleged NiCd "memory effect". Another
possibility is that some support droid needed a line to get rid of a
complaining customer and invented the "conditioning" for the purpose.

The inherent lower terminal voltage and cell mAH capacity were the real
reasons.

Agreed. I went through the mess with alleged "9V" (6 cell) NiCd
batteries, being more like 7.2VDC. With a nominal operating voltage
for 1.2 to 1.3 VDC for NiCd and NiMH, anything designed for a 1.5VDC
alkaline is going to have a problem.

Incidentally, all of the marine radios I helped design were required
to function down to 10.0VDC applied power. They couldn't reach rated
TX power at 70% of rated voltage, but still had to belch at least a
few watts of RF and remain functional.

I'm rather mystified by the results. Although the improvement in
capacity after 3 charge-discharge cycles is minor (10-15%), it still
seems for real. My previous tests didn't show such an increase in
capacity. Instead, it showed a deterioration in capacity. However, I
was testing for something quite different, and was working with a mix
of old and new cells.

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

 

[Phil Allison]

"Jeff Liebermann"

** You got something against NiMh cells ?

Yep. I don't like them.

** Wanker.

I would never mistreat NiMH AA cells the way you just have.

I didn't have time to do it the right way (20 hr discharge).

** The 15 min charging was the abuse - fool.

I can do
it again with a longer discharge time and lower current.

** The 15 min charging was the abuse - fool.

15 minute charging is absurd for any cell NOT designed for such abuse - it
causes overheating with new cells and destruction of older ones.

True for the Duracell,

** True for all of them - fool.

However, the recommended battery charger is a quick charger:
http://data.energizer.com/PDFs/ch15mn2.pdf
with a 15 minute charge time.

** They would - since they sell the fucking things.

Energiser sell a whole range of chargers designed to destroy NiMh cells.

Means they sell more cells.

I've been testing batteries since about 2005

** I've been doing it since 1979.

However, I will point out that many
NiCd batteries can be quick charged at ridiculously high rates,

** Only a rare few, specially designed NiCds were designed for it -
Sanyo's red " F " cells being one.

The issue is the HIGH probability of OVERCHARGING and hence over heating
with consequent internal damage.

Incidentally, the Sanyo ENELOOP battery data sheet recommends fast
charging at 2A for 1.1 hrs:
http://www.eneloop.info/fileadmin/EDITORS/ENELOOP/DATA_SHEETS/HR-3UTGA_data_sheet.pdf

** Got nothing to do with a 15 minute charge in a cheap POS charger like you
did.

A 1C discharge test will never give the rated capacity figure with NiCd or
NiMH.

I indicated that in my posting as:

I didn't want to wait 20 hrs per test to get the official rated
capacity, so I elected to run the tests at 1C which resulted in about
a 45 minute test, but also resulted in a much lower capacity result.

** Will you admit to being a raving lunatic ???

And save me the trouble of demonstrating it to the world over and over.

IME - the idea that new cells have a "running in "period is a MYTH
invented by retailers back in the 1970s when consumers were first sold AA
and C size NiCds and found their performance disappointing when compared
to
alkalines.

Maybe.

** Definitely.

The inherent lower terminal voltage and cell mAH capacity were the real
reasons.

Agreed.

** No elaboration was needed.

I'm rather mystified by the results.

** Bad science is no mystery.


...... Phil

 

[Dave Platt]

In article <3kt8u69j7d6i3cetop4hgcjfsv92ek2s8r@4ax.com>,
Jeff Liebermann <jeffl@cruzio.com> wrote:

True for the Duracell, which recommends 205ma for 15 hrs to recharge
printed on the cell. The Energizer Recharge battery doesn't specify a
charge current:
http://data.energizer.com/PDFs/nh15-2000.pdf
However, the recommended battery charger is a quick charger:
http://data.energizer.com/PDFs/ch15mn2.pdf
with a 15 minute charge time.

I've been testing batteries since about 2005 while working on a
product that I won't discuss. However, I will point out that many
NiCd batteries can be quick charged at ridiculously high rates, as
long as certain (unspecified) conditions are met. If you don't mind,
I'll leave this unsubstantiated.

Incidentally, the Sanyo ENELOOP battery data sheet recommends fast
charging at 2A for 1.1 hrs:
http://www.eneloop.info/fileadmin/EDITORS/ENELOOP/DATA_SHEETS/HR-3UTGA_data_sheet.pdf

Interesting. Another page in the Sanyo FAQ section (at
http://us.sanyo.com/eneloop/FAQs) says:

Though it is possible to charge an eneloop battery in a "Quick
Charger", it is not recommended. We recommend charging eneloop
batteries in a NiMh charger that is 2 hours or more. Charging eneloop
batteries in a "Quick Charger" can reduce the overall life of the
battery.

I've read statements to the effect that one reason you would want to
use moderately-fast charging rates (e.g. 1C) rather than the low rates
traditional for most NiCd cells (e.g. 0.1C), is that the NiMH cells
will heat up more abruptly when they reach full charge, and the
charging power starts turning into heat rather than electrochemical
potential. The abrupt rise in cell temperature is easier to detect
reliably (via a temperature sensor and/or due to the zero-delta-V
effect) than if you were charging more slowly... and thus a more
reliable "full charge, stop now!" shutoff circuit can be designed, and
avoid overcharging (which I understand NiMH cells don't tolerate at
all well).

Incidentally, all of the marine radios I helped design were required
to function down to 10.0VDC applied power. They couldn't reach rated
TX power at 70% of rated voltage, but still had to belch at least a
few watts of RF and remain functional.

A good decision! It bothers me that a lot of HF and VHF radios "poop
out" at much below 12 volts.

I'm rather mystified by the results. Although the improvement in
capacity after 3 charge-discharge cycles is minor (10-15%), it still
seems for real. My previous tests didn't show such an increase in
capacity. Instead, it showed a deterioration in capacity. However, I
was testing for something quite different, and was working with a mix
of old and new cells.

For what it's worth, the Sanyo FAQ page cited above does make
reference to the break-in effect:

Should I store my batteries charged or uncharged?

If stored with charge, it is possible that when you return to use
the battery there may still be some charge left in the battery,
therefore it will enable you to use it right then and there. Also,
by keeping some charge in the battery, it will require you to
"cycle" the battery fewer times until it reaches its peak charge.
If you store them with no charge, you will have to "cycle" the
battery multiple times until it reaches its peak charge.


--
Dave Platt <dplatt@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!

 

[William Sommerwerck]

Though it is possible to charge an eneloop battery in a
"Quick Charger", it is not recommended. We recommend
charging eneloop batteries in a NiMh charger that is [sic]
2 hours or more. Charging eneloop batteries in a "Quick
Charger" can reduce the overall life of the battery.

A two-hour charge is, by any reasonable standard, a "quick charge". It would
be at least 0.5C -- hardly a slow charge.

 

[Phil Allison]

"William Sommerwanker"

Though it is possible to charge an eneloop battery in a
"Quick Charger", it is not recommended. We recommend
charging eneloop batteries in a NiMh charger that is [sic]
2 hours or more. Charging eneloop batteries in a "Quick
Charger" can reduce the overall life of the battery.

A two-hour charge is, by any reasonable standard, a "quick charge". It
would
be at least 0.5C -- hardly a slow charge.

** Standard charge for a NiMH is 16 hours at 0.1C.

Quick chargers deliver about 0.2C to 0.5 C

Fast chargers deliver 1C to 4C ( ouch ! )

Because NiMH ( AA, A or 9V ) cells vary widely in rated capacity - the same
charger has multiple rates.

So called " simple " chargers have a timer as the only cut out.

A 4C fast charger that only has a timer is a lethal weapon.

IME - the worst offenders in supplying chargers that are practically
guaranteed to ruin the cells are the battery makers - ie Energiser, Varta
and Sanyo.

Funny about that.



..... Phil

 

[William Sommerwerck]

"Phil Allison" <phil_a@tpg.com.au> wrote in message
news:94ljveFq68U1@mid.individual.net...

"William Sommerwanker"

I thought you'd reformed. But you haven't. Why don't you just go back to
being a foul-mouthed jerk? That's what you want, isn't it? You want people
to hate you, because it makes you feel superior.

The worst part is that when you aren't making nasty remarks, you almost
always have somthing worth hearing.

Our own little Eric Cartman. How charming.

Though it is possible to charge an eneloop battery in a
"Quick Charger", it is not recommended. We recommend
charging eneloop batteries in a NiMh charger that is [sic]
2 hours or more. Charging eneloop batteries in a "Quick
Charger" can reduce the overall life of the battery.

A two-hour charge is, by any reasonable standard, a "quick charge".
It would be at least 0.5C -- hardly a slow charge.

** Standard charge for a NiMH is 16 hours at 0.1C.
Quick chargers deliver about 0.2C to 0.5 C
Fast chargers deliver 1C to 4C (ouch!)
Because NiMH ( AA, A or 9V ) cells vary widely in rated capacity --
the same charger has multiple rates.

So-called "simple" chargers have a timer as the only cutout.
A 4C fast charger that only has a timer is a lethal weapon.

IME -- the worst offenders in supplying chargers that are practically
guaranteed to ruin the cells are the battery makers -- ie Energizer,
Varta, and Sanyo.
Funny about that.

As they sell batteries, why should it be funny?

Based on my experience at Microsoft Hardware, and MAHA's documentation, 0.1C
is not considered an appropriate charge rate for NiMH cells. Higher rates
are recommended, supposedly because they pump more charge into the cell
before the cutoff voltage or temperature is reached.

I rarely charge faster than 0.3C. That's just basic cowardice on my part.

 

[Phil Allison]

"William Sommerwanker = Colossal FUCKWIT "

A two-hour charge is, by any reasonable standard, a "quick charge".
It would be at least 0.5C -- hardly a slow charge.

** Standard charge for a NiMH is 16 hours at 0.1C.
Quick chargers deliver about 0.2C to 0.5 C
Fast chargers deliver 1C to 4C (ouch!)
Because NiMH ( AA, A or 9V ) cells vary widely in rated capacity --
the same charger has multiple rates.

So-called "simple" chargers have a timer as the only cutout.
A 4C fast charger that only has a timer is a lethal weapon.

IME -- the worst offenders in supplying chargers that are practically
guaranteed to ruin the cells are the battery makers -- ie Energizer,
Varta, and Sanyo.
Funny about that.

As they sell batteries, why should it be funny?

** FFS - the irony is pretty damn strong.

Not to mention being contrary to consumer law.

Based on my experience at Microsoft Hardware, and MAHA's documentation,
0.1C
is not considered an appropriate charge rate for NiMH cells.

** Totally IRRELEVANT.

For * loose cells * sold to the public and in the absence of " smart "
chargers that treat each cell as in individual - it is the only reliably
safe method.

Higher rates
are recommended, supposedly because they pump more charge into the cell
before the cutoff voltage or temperature is reached.

** Requires a smart charger, matched packs of cells et alia ad nauseam.

A whole different ball game.

I rarely charge faster than 0.3C.

** Still well capable of ruining NiMH cells left on charge for too long.

BTW:

Ruining refers to a simultaneous loss of capacity and LARGE increases in
self discharge rate and internal resistance.


..... Phil

 

[William Sommerwerck]

"Phil Allison" <phil_a@tpg.com.au> wrote in message
news:94lmqvFcfeU1@mid.individual.net...

Higher rates
are recommended, supposedly because they pump more charge
into the cell before the cutoff voltage or temperature is reached.

** Requires a smart charger, matched packs of cells et alia ad nauseam.
A whole different ball game.

Not for me. I own two smart chargers.

I rarely charge faster than 0.3C.

** Still well capable of ruining NiMH cells left on charge for too long.

See preceding.

 

[Phil Allison]

"William Sommerwanker = Context Shifter and LIAR "


** DROP FUCKING DEAD

 

[Jeff Liebermann]

On Tue, 31 May 2011 11:27:21 -0700, dplatt@radagast.org (Dave Platt)
wrote:

Interesting. Another page in the Sanyo FAQ section (at
http://us.sanyo.com/eneloop/FAQs) says:

Though it is possible to charge an eneloop battery in a "Quick
Charger", it is not recommended. We recommend charging eneloop
batteries in a NiMh charger that is 2 hours or more. Charging eneloop
batteries in a "Quick Charger" can reduce the overall life of the
battery.

Like the alleged increase in NiMH capacity produced by initially
"conditioning" the battery, there's the question of how much does
quick charging a battery reduce its overall life? According to
various documents which I'm too lazy to find, a cell is considered
dead when it reaches 50% of its rated capacity. One text mumbled that
quick charging will reduce the number of charge cycles by 20%. For a
400 to 800 charge cycle battery, that would be not a big deal for
cheapo AA cells, and a major cost issue for expensive radio battery
packs.

My guess(tm) is that internal heating is doing the damage. With a
defacto standard 16r 0.1C charge, there's some excess power going into
heat. For a perfect battery, 10 hrs of this 0.1C is all that's
required to get to 100%. The other 6 hrs of charge is going
somewhere, most likely into heat. Over a 16 hr charge, that's not
going to heat up the battery much. Over a 0.25 hr 4C charge, that's
quite a bit of power heating the battery. Note that the internal
resistance (ESR) of the battery also heats the battery on discharge,
making a rapid discharge risky.

So, why the wide variation in capacity and recommended charging
methods? Because none of them will satisfy everyone. If you ask
marketing, they will offer the highest possible science fiction
capacity, over unrealistic discharge times (20 hr), with the fastest
possible (4C) recharge because that's what consumers want. If you ask
the company legal counsel, they will offer a much lower capacity to
avoid getting sued, and the safest possible recharge method, for the
same reason. Everyone lies, but that's ok because nobody listens.

The problem is that I don't have the time to run a proper test. I
could take one of the brand new Energizer cells, charge at 4C (15
min), discharge at 1C (about 45 min), and repeat as many times as it
takes for the battery capacity to drop 50% from 2300 ma-hr. Without
automation, my guess is that I can do about 4 cycles per day. That
will take 3 months before I kill the battery.

I've read statements to the effect that one reason you would want to
use moderately-fast charging rates (e.g. 1C) rather than the low rates
traditional for most NiCd cells (e.g. 0.1C), is that the NiMH cells
will heat up more abruptly when they reach full charge, and the
charging power starts turning into heat rather than electrochemical
potential.

Sorta. The amount of heat (calories) produced by fast or slow
charging is the same. However, with fast charge, the heat is produced
over a much shorter period, resulting in a much higher cell
temperature. Methinks it's this temperature that kills the cells.

Incidentally, I learned the hard way with NiCd batteries that once the
heat gets to the case and is able to be measured, it's too late. The
internal damage is already done. Internal sensors are required.

Note the magnetic temperature sensor on my battery fixture (that has
fallen off and landed on the spring).
<http://802.11junk.com/jeffl/NiMH/cba-II.jpg>

The abrupt rise in cell temperature is easier to detect
reliably (via a temperature sensor and/or due to the zero-delta-V
effect) than if you were charging more slowly... and thus a more
reliable "full charge, stop now!" shutoff circuit can be designed, and
avoid overcharging (which I understand NiMH cells don't tolerate at
all well).

Yep. Quick charging will produce a higher cell temperature which is
easier to detect.

During my experiments with NiCd batteries, I've found that I can
charge a single cell at almost any rate (I've done 20C). As long as
the battery is below 100% capacity, there is almost no heating. As
the battery approaches about 95% of capacity, the heating starts, and
rapidly increases. I've quick charged 650 ma-hr NiCd batteries to
almost full charge in about 3 minutes. However, there's a catch. If
I miss the 95% point, and go over, the overcharge will either kill the
battery, or vent boiling caustic electrolyte. It's for this reason
that I suspect really quick chargers are not sold or recommended. I
have not done any such testing with NiMH.

A good decision! It bothers me that a lot of HF and VHF radios "poop
out" at much below 12 volts.

Fishing boats like to run quiet, with the engine off. There are also
sailboats and small boats that only charge the battery at the dock.
(These daze, they have solar chargers). It's not unusual for them to
use crappy batteries, that have a no charge terminal voltage of
10-11VDC. Getting 10 watts output from a 25w bipolar Class-C stage at
10VDC was not easy.

For what it's worth, the Sanyo FAQ page cited above does make
reference to the break-in effect:

Should I store my batteries charged or uncharged?

If stored with charge, it is possible that when you return to use
the battery there may still be some charge left in the battery,
therefore it will enable you to use it right then and there. Also,
by keeping some charge in the battery, it will require you to
"cycle" the battery fewer times until it reaches its peak charge.
If you store them with no charge, you will have to "cycle" the
battery multiple times until it reaches its peak charge.

Note the misuse of the words "peak charge". It should say "peak
capacity". Kinda reads like this was written by marketeering, not
engineering. If they had mentioned that ignoring this sage advice
might result in an initial loss of 10-15% of peak capacity (per my
tests), I suspect that users would probably ignore the problem.
However, because the effect is not innumerated, it looks a major
problem.

So, if I cycle a new NiMH battery with a 4C charge, and a 1C
discharge, how many cycles would you guess I would get before the
battery hits 50% of rated capacity? The winner gets what's left of
the test battery (suitable for recycling) when I'm done.

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

 

[Jeff Liebermann]

On Wed, 01 Jun 2011 08:54:57 -0700, Jeff Liebermann <jeffl@cruzio.com>
wrote:

Sorta. The amount of heat (calories) produced by fast or slow
charging is the same. However, with fast charge, the heat is produced
over a much shorter period, resulting in a much higher cell
temperature. Methinks it's this temperature that kills the cells.

That kinda begs the question if submerging the cell in cooling water
will allow for a fast charge (4C) without overheating and killing the
battery? I can see it now... the super-fast battery charger, just add
coolant.

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

 

[William Sommerwerck]

Several years ago I ran tests using name-brand AA alkalines and 2500mAh NiMH
cells to power a STAX headphone amplifier. (This was not completely valid,
because I had no idea what the alkaline cells' rated capacity was. Does
anybody know?)

Much to my surprise, I discovered that the rechargeable cells powered the
unit as long as the throwaways. This means I'd break even after only 10
recharges. Even if I was off by 50%, I'd still need only 20 recharges.

The shortened life of fast recharging has to be weighed against the cost of
using throwaways. In practice -- particularly with heavy-drain devices --
you don't need many charge/recharge cycles to break even.

This is why I carry multiple sets of NiMH cells for my flashes and other
heavy-drain devices. With multiple sets, I don't have to worry about rapid
recharging, and can stick with 0.2C or 0.3C.

 

[Jeff Liebermann]

On Wed, 1 Jun 2011 09:06:40 -0700, "William Sommerwerck"
<grizzledgeezer@comcast.net> wrote:

Several years ago I ran tests using name-brand AA alkalines and 2500mAh NiMH
cells to power a STAX headphone amplifier. (This was not completely valid,
because I had no idea what the alkaline cells' rated capacity was. Does
anybody know?)

It varies radically with load. With a very light load, it's as high
as 2000 ma-hr. With a heavy 1 amp load, as little as 550 ma-hr.
However, even that's not consistent. I was comparing Costco Kirkland
alkaline AA batteries, with the equivalent Duracell, Ray-o-Vac, etc
cells. The cheapo Kirkland cells were far better with a 1A load, but
sucked with a light load. Duracell was the exact opposite. The
differnces were not huge, but they were reproducable.

More than you ever wanted to know about alkaline batteries:
<http://www.powerstream.com/AA-tests.htm>
Note the variations by brand and type and the NiMH cell in the bottom
graph.

Much to my surprise, I discovered that the rechargeable cells powered the
unit as long as the throwaways. This means I'd break even after only 10
recharges. Even if I was off by 50%, I'd still need only 20 recharges.

Headphone amps sound like a light load. Got a number for the average
current drain?

The shortened life of fast recharging has to be weighed against the cost of
using throwaways. In practice -- particularly with heavy-drain devices --
you don't need many charge/recharge cycles to break even.

I killed a small Canon camera by using alkalines. It was apparently
designed for the normal terminal voltages found with NiCd and NiMH.
When I stuffed in an alkaline cell, the camera overheated after about
30 shots, and died. Canon covered it under the warranty.

Also, NiMH can handle short duration high current loads much better
than alkaline. That's they type of load found in many digital
cameras. Alkaline might be an option for a low current load such as
your headphones, but they wouldn't last long in a high current camera.

This is why I carry multiple sets of NiMH cells for my flashes and other
heavy-drain devices. With multiple sets, I don't have to worry about rapid
recharging, and can stick with 0.2C or 0.3C.

I've had problems with self discharge in previous NiMH batteries. So,
I have a 117VAC/12DC fast (4C / 15 min) charger in the camera bag.
When I need to shoot lots of photos, I give it a quick charge. Maybe
the LSD (low self discharge) NiMH will eliminate this problem.

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

 

[Jeff Liebermann]

On Wed, 01 Jun 2011 08:54:57 -0700, Jeff Liebermann <jeffl@cruzio.com>
wrote:

More on how NiMH charging:
<http://www.powerstream.com/NiMH.htm>

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

 

[William Sommerwerck]

"Jeff Liebermann" <jeffl@cruzio.com> wrote in message
news:ddpcu69fvgl4lb0fml8hsultltcmslgehi@4ax.com...

On Wed, 1 Jun 2011 09:06:40 -0700, "William Sommerwerck"
grizzledgeezer@comcast.net> wrote:

Much to my surprise, I discovered that the rechargeable cells powered the
unit as long as the throwaways. This means I'd break even after only 10
recharges. Even if I was off by 50%, I'd still need only 20 recharges.

Headphone amps sound like a light load. Got a number for the average
current drain?

The operative word here is STAX -- as in high-voltage electrostatic
earphones. I never measured the drain, but neither set of cells lasted much
more than four hours.

This is why I carry multiple sets of NiMH cells for my flashes and other
heavy-drain devices. With multiple sets, I don't have to worry about
rapid
recharging, and can stick with 0.2C or 0.3C.

I've had problems with self discharge in previous NiMH batteries. So,
I have a 117VAC/12DC fast (4C / 15 min) charger in the camera bag.
When I need to shoot lots of photos, I give it a quick charge. Maybe
the LSD (low self discharge) NiMH will eliminate this problem.

We still don't have a rational answer as to why some people don't have
problems with rapid self-discharge.

I don't shoot every day, so I can charge-up the night before. I have two
chargers, which makes things easier.

 

[Jeff Liebermann]

On Wed, 1 Jun 2011 10:31:48 -0700, "William Sommerwerck"
<grizzledgeezer@comcast.net> wrote:

"Jeff Liebermann" <jeffl@cruzio.com> wrote in message
news:ddpcu69fvgl4lb0fml8hsultltcmslgehi@4ax.com...
On Wed, 1 Jun 2011 09:06:40 -0700, "William Sommerwerck"
grizzledgeezer@comcast.net> wrote:

Much to my surprise, I discovered that the rechargeable cells powered the
unit as long as the throwaways. This means I'd break even after only 10
recharges. Even if I was off by 50%, I'd still need only 20 recharges.

Headphone amps sound like a light load. Got a number for the average
current drain?

The operative word here is STAX -- as in high-voltage electrostatic
earphones. I never measured the drain, but neither set of cells lasted much
more than four hours.

$2,000 for earphones and you're worrying about the price of
rechargeable batteries? Argh.

There seems to be two amps. One with tubes and the other presumably
IC's.
<http://www.stax.co.jp/Export/ExportProducts.html>
55 watts and 46 watts power consumption from an internal 117VAC power
supply. No batteries in sight. Wrong unit?

We still don't have a rational answer as to why some people don't have
problems with rapid self-discharge.

Oh, that's easy. How many charge cycles would you guess you get on a
set of NiMH before they're ready to recycle? You probably don't know
and neither does Joe Sixpack. I don't even know because nobody is
counting. So, Joe Sixpack may get 2 years of service out his NiMH
battery pack, but has only charged it perhaps 20 times before it died.
I vaguely know someone that maintains TV camera battery packs for one
of the major networks. Current technology is Li-Ion but in the not so
distant past, it was NiMH and NiCd. He keeps meticulous records. I
must admit that I wasn't paying attention when he showed me the
numbers, but it seemed to me that even for identical battery packs,
the numbers were almost random. Some would last on a few charge
cycles, while other would last seemingly forever. He attributed this
mostly to depth of charge and storage temperature. Even the best
battery, stored hot, will die prematurely. This is a known problem
with Li-Ion, but I'm not sure if storage temperature has any effect on
NiMH. Mine are all in the fridge, just in case. Depth of charge is
the biggie. A battery that is only discharged to perhaps 75% of full
charge, can be charge cycled many more times than one that is fully
discharged before recharging. However, if the charger is too
aggressive, a battery that's discharged to 75% might be overcharged,
while the one that's fully discharged is less likely to be
overcharged.

I don't shoot every day, so I can charge-up the night before. I have two
chargers, which makes things easier.

I have 3 fast chargers. House, office, and vehicle. The one in the
vehicle seems to get the most use.

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

 

[William Sommerwerck]

"Jeff Liebermann" <jeffl@cruzio.com> wrote in message
news:gk1du65nn8ipkgboqqji1b9gkhmtds5in0@4ax.com...

On Wed, 1 Jun 2011 10:31:48 -0700, "William Sommerwerck"
grizzledgeezer@comcast.net> wrote:

The operative word here is STAX -- as in high-voltage electrostatic
earphones. I never measured the drain, but neither set of cells
lasted much more than four hours.

$2,000 for earphones and you're worrying about the price of
rechargeable batteries? Argh.

No, they were more like $350. I said earphones, not headphones.

There seems to be two amps. One with tubes and the other presumably
IC's.
http://www.stax.co.jp/Export/ExportProducts.html
55 watts and 46 watts power consumption from an internal 117VAC power
supply. No batteries in sight. Wrong unit?

Wrong units. This is a pocket-sized transformerless energizer that runs off
two AA cells. It works with a tiny pair of electrostatic earphones.

We still don't have a rational answer as to why some people don't have
problems with rapid self-discharge.

Oh, that's easy. How many charge cycles would you guess you get on a
set of NiMH before they're ready to recycle? You probably don't know
and neither does Joe Sixpack. I don't even know because nobody is
counting. So, Joe Sixpack may get 2 years of service out his NiMH
battery pack, but has only charged it perhaps 20 times before it died.
I vaguely know someone that maintains TV camera battery packs for one
of the major networks. Current technology is Li-Ion but in the not so
distant past, it was NiMH and NiCd. He keeps meticulous records. I
must admit that I wasn't paying attention when he showed me the
numbers, but it seemed to me that even for identical battery packs,
the numbers were almost random. Some would last on a few charge
cycles, while other would last seemingly forever. He attributed this
mostly to depth of charge and storage temperature. Even the best
battery, stored hot, will die prematurely. This is a known problem
with Li-Ion, but I'm not sure if storage temperature has any effect on
NiMH. Mine are all in the fridge, just in case. Depth of charge is
the biggie. A battery that is only discharged to perhaps 75% of full
charge, can be charge cycled many more times than one that is fully
discharged before recharging. However, if the charger is too
aggressive, a battery that's discharged to 75% might be overcharged,
while the one that's fully discharged is less likely to be
overcharged.

That's extremely useful information, but I'm still not sure it answers the
question -- unless you're suggesting that the people who have problems with
rapid self-discharge have damaged their cells.

 

[Jeff Liebermann]

On Wed, 1 Jun 2011 12:12:03 -0700, "William Sommerwerck"
<grizzledgeezer@comcast.net> wrote:

No, they were more like $350. I said earphones, not headphones.

Pardon my ignorance, but what is the difference between earphones and
headphones? I use the terms interchangeably.

That's extremely useful information, but I'm still not sure it answers the
question -- unless you're suggesting that the people who have problems with
rapid self-discharge have damaged their cells.

Nope. A one line summary would be that most users don't remember how
many times they have charged their NiMH cells, don't recall how old
they are, and have no clue as what constitutes normal lifetime. If
someone has a battery killer in the form of a battery charger, they
would just continue to use it, killing battery after battery, without
ever doing the math needed to determine if something is wrong.

Even simpler... do *YOU* record the number of charge cycles of your
rechargeable batteries? If not, then you have no accurate way to
determine if you're getting the normal number of charge cycles
(400-800) from the NiMH batteries (unless you have a really good
memory).


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