Quick charger vs Slow: Which last longer NiMH batteries?

On Thu, 01 Jan 2009 13:39:43 -0500, ASAAR wrote in
:

[SNIP]

Into the twit filter you go.

--
Very best wishes for the holiday season and for the coming new year,
John

The experts sat that it doesn't matter if the charger is properly
designed. The life of a NiMH battery is defined by a number of charges.
Of course the end of life is not sudden, but a gradual predictable
decrease in the storage capacity. So in battery studies, the end of
life is when there is a certain percentage reduction in the storage
capacity. If the life is X number of charges, then if you half
discharge it and then recharge it, you can get 2x half-charges. Etc.
This is not completely true since if kept on continuous trickle charge,
they will still fail eventually.

My experience with NiMH batteries is that Radio Shack batteries last as
long as any of the better batteries. The only brand that had early
mortality was an expensive SunPak set. However, my SunPak charger is
still alive and well and a Radio Shack charger I bought is dead.

I keep 18 batteries at all times. One set of 4 for the camera. One set
of 2 for the flash. 2 spare sets for the camera and the flash. I have
them numbered so that the sets are rotated and used equally. A set is
never broken. They are always purchased together, used together and
charged together.

NiMH batteries are fairly robust. On the other hand, Lithium batteries
are light, but they are not robust. The can be destroyed by completely
discharging. Some brands of lithium batteries are much more fragile.

--
Pardon my spam deterrent; send email to
Cheers, Steve Henning in Reading, PA USA - http://rhodyman.net

On Thu, 01 Jan 2009 10:56:32 -0800, John "Twitty" Navas wrote:

[SNIP]

Into the twit filter you go.

I'd say "your loss", but you lost it long ago. Too bad that you
can't tolerate when it's pointed out that your condescending remarks
are either irrelevant or incorrect. The fuller your filter sack
becomes, the greater your burden. You'll still be corrected as
necessary, and if you don't see the corrections there won't be any
loss as you wouldn't benefit from them even if you could see them.

Stephen Henning wrote:
[]
NiMH batteries are fairly robust. On the other hand, Lithium
batteries are light, but they are not robust. The can be destroyed
by completely discharging. Some brands of lithium batteries are much
more fragile.

Lithium primary cells or Li-ion rechargeable? To me, the packaging shape
is probably more important - I much prefer the single rectangular cell to
multiple batteries which can be inserted the wrong way round. I like the
lower self-discharge of Li-ion or Eneloops.

David

On Thu, 01 Jan 2009 15:28:25 -0500, Stephen Henning
wrote in :

The experts sat that it doesn't matter if the charger is properly
designed. The life of a NiMH battery is defined by a number of charges.
Of course the end of life is not sudden, but a gradual predictable
decrease in the storage capacity. So in battery studies, the end of
life is when there is a certain percentage reduction in the storage
capacity. If the life is X number of charges, then if you half
discharge it and then recharge it, you can get 2x half-charges. Etc.
This is not completely true since if kept on continuous trickle charge,
they will still fail eventually.

What "experts"? According to battery manufacturers, life can be
affected by charging, particularly in cases of overheating and
overcharging.

NiMH batteries are fairly robust. On the other hand, Lithium batteries
are light, but they are not robust. The can be destroyed by completely
discharging. Some brands of lithium batteries are much more fragile.

NiMH batteries will also be destroyed by complete discharge. Look up
"polarity reversal".

Energizer NICKEL-METAL HYDRIDE Application Manual
http://data.energizer.com/PDFs/nickelmetalhydride_appman.pdf

--
Very best wishes for the holiday season and for the coming new year,
John

On 1/1/09 12:56 PM, in article ,
"John Navas" wrote:

On Thu, 01 Jan 2009 13:39:43 -0500, ASAAR wrote in
:

[SNIP]

Into the twit filter you go.
Me too! PLEASE! Mee 22...

On Thu, 01 Jan 2009 13:26:38 -0800, Non-expert John Navas wrote:

The experts sat that it doesn't matter if the charger is properly
designed. The life of a NiMH battery is defined by a number of charges.
. . .

What "experts"? According to battery manufacturers, life can be
affected by charging, particularly in cases of overheating and
overcharging.

Heating is a normal part of the charge cycle. Overheating, enough
to cause batteries to vent and lose capacity or worse, is not by any
means normal, and is not due to good or poor charger design, but due
to defective batteries or chargers.


NiMH batteries are fairly robust. On the other hand, Lithium batteries
are light, but they are not robust. The can be destroyed by completely
discharging. Some brands of lithium batteries are much more fragile.

NiMH batteries will also be destroyed by complete discharge. Look up
"polarity reversal".

Don't you know the difference between complete discharge and
reverse charge? One can produce polarity reversal. The other
won't. Try putting a NiMH AA cell in a single AA cell flashlight.
Turn it on. How long do you think it will take for the cell to
achieve polarity reversal? The only thing destroyed here, once
again, is your credibility. [as if this wasn't expected! ]
Despite having relatively low self-discharge rates, Li-Ion batteries
can fail completely if they go too long without being charged. They
don't need a full charge, just a few minutes on the charger every 6
months or so is good enough. I didn't have to look it up. This was
part of the notes included with several after-market Li-Ion battery
packs, and later verified several years ago in the ng by a couple of
users who had put their cameras away in drawers for too many
consecutive months of non-use (and non-charge).

John Navas wrote:

Stephen Henning wrote:

The experts sat that it doesn't matter if the charger is properly
designed. The life of a NiMH battery is defined by a number of charges.
Of course the end of life is not sudden, but a gradual predictable
decrease in the storage capacity. So in battery studies, the end of
life is when there is a certain percentage reduction in the storage
capacity. If the life is X number of charges, then if you half
discharge it and then recharge it, you can get 2x half-charges. Etc.
This is not completely true since if kept on continuous trickle charge,
they will still fail eventually.

What "experts"? According to battery manufacturers, life can be
affected by charging, particularly in cases of overheating and
overcharging.

That is why they say with a "PROPERLY DESIGNED" battery charger it
doesn't matter. Some properly designed chargers us a temperature
measurement and others use detailed voltage measurements.

NiMH batteries are fairly robust. On the other hand, Lithium batteries
are light, but they are not robust. The can be destroyed by completely
discharging. Some brands of lithium batteries are much more fragile.

NiMH batteries will also be destroyed by complete discharge. Look up
"polarity reversal".

Polarity reversal is caused when more than one cell is discharged. The
last one to discharge reverses the polarity of the other(s). It doesn't
always happen, but can happen. Just discharging a single cell will not
cause polarity reversal.

--
Pardon my spam deterrent; send email to
Cheers, Steve Henning in Reading, PA USA - http://rhodyman.net

On Fri, 02 Jan 2009 00:03:28 -0500, Stephen Henning
wrote in :

John Navas wrote:

What "experts"? According to battery manufacturers, life can be
affected by charging, particularly in cases of overheating and
overcharging.

That is why they say with a "PROPERLY DESIGNED" battery charger it
doesn't matter. Some properly designed chargers us a temperature
measurement and others use detailed voltage measurements.

True.

NiMH batteries will also be destroyed by complete discharge. Look up
"polarity reversal".

Polarity reversal is caused when more than one cell is discharged. The
last one to discharge reverses the polarity of the other(s). It doesn't
always happen, but can happen. Just discharging a single cell will not
cause polarity reversal.

False.

Damaging polarity reversal can occur with a single cell.
From the authoritative link I posted:

Discharge Termination

To prevent the potential for irreversible harm to the cell caused by
cell reversal in discharge, removal of the load from the cell(s)
prior to total discharge is highly recommended. The typical voltage
profile for a cell carried through a total discharge involves a dual
plateau voltage profile as indicated in Figure 14. The voltage
plateaus are caused by the discharge of first the positive electrode
and then the residual capacity in the negative. At the point both
electrodes are reversed, substantial hydrogen gas evolution occurs,
which may result in cell venting as well as irreversible structural
damage to the electrodes. It should be noted that the nickel-metal
hydride cell, because it uses a negative electrode that absorbs
hydrogen, might actually be somewhat less susceptible to long-term
damage from cell reversal than the sealed nickel-cadmium cell.

The key to avoiding harm to the cell is to terminate the discharge at
the point where essentially all capacity has been obtained from the
cell, but prior to reaching the second plateau where damage may
occur. ...

There's more. Suggest you read it this time.

--
Very best wishes for the holiday season and for the coming new year,
John

On Fri, 02 Jan 2009 10:27:10 -0800, John Navas wrote:

The key to avoiding harm to the cell is to terminate the discharge at
the point where essentially all capacity has been obtained from the
cell, but prior to reaching the second plateau where damage may
occur. ...

There's more. Suggest you read it this time.

You need to follow this advice even more. The real, significant
damage occurs when additional cells that still have capacity left
force the depleted cell beyond zero volts into negative territory
where the two voltage plateaus exist. At that time reversal already
occurred, and it doesn't happen to single cells. The authoritative
source you quoted from specifically talks of the cell being carried
"through", not "to" total discharge. The "potential for irreversal
harm to the cell" was also a clue missed by you, specifically the
word "potential". The two voltage plateaus are seen in Energizer's
chart, the first appearing at about -0.3 volts and the second at
about -1.8 volts. Multiple cells driving current through a depleted
cell are required to do this, and Energizer specifically warns of
the damage that might occur due to cell venting at this lower, -1.8
volt plateau. Your quote ended with this :

The key to avoiding harm to the cell is to terminate the discharge at
the point where essentially all capacity has been obtained from the
cell, but prior to reaching the second plateau where damage may
occur. ...

There's more. Suggest you read it this time.


The "more" that you didn't quote, and which immediately followed
"where damage may occur. ..." was this :


Two issues complicate the selection of the proper voltage for
discharge termination: high-rate discharges and multiple-cell
effects in batteries.

Get it? Multiple-cell effects. Single cell devices won't
seriously damage NiMH AA cells. Even those that use two cells are
pretty safe, since with one "dead" cell contributing no voltage to
the help the current flow, and the other cell contributing probably
less than 1.1 volts (and some of that appearing only across the
device), there's no way that the dead cell will be forced as low as
-1.8 volts, as that would indicate that the "dead" cell was able to
reverse the current flow through the "good" cell, in effect charging
it, and this doesn't even begin to touch on what would be happening
to the device, but it would be akin to installing good batteries in
it, but backwards in their slots.

With multi-cell devices, cell reversal can happen without the user
being aware that this is happening, especially if more than 4 cells
are used. Most or all digital cameras will power down long before
this can occur. With single cell devices, even the most clueless
would have long seen a need to remove and recharge the cell in the
non-functioning device. And if not, little or no harm would occur
anyway.

Good tools are only at their most useful when in the right hands.
Good battery application manuals also need to be in the right hands
to be useful. Your hands don't qualify. Misunderstanding and
shortening quotes to eliminate context and create the opposite of
Energizer's intent demonstrates your lack of qualification. But
what else is new? Good thing for you that you won't read this
unless it's quoted by someone not already added to your large and
growing kill filter!