Wild_Bill wrote:
I've been doing a lot of reading wrt battery cell testing, but have only
seen one (affordable, reasonably priced) recommendation for testing
rechargeable cell ESR.. the Bob Parker ESR Meter.

http://www.flippers.com/esrkthnt.html (near the bottom)
http://www.prc68.com/I/BatTst.shtml#EVB

I would like to be able to determine (actually see it) if zapping new
nicad cells improves (lowers) cell internal resistance, or to just check
cells for a parameter other than voltage.
From what I've found, zapping new NIMH cells isn't worthwhile, or
attempts have been inconclusive.

I want to avoid any testing equipment that requires a computer. I also
don't want to build battery packs with the newer fuel gage technology
electronics.

I'm not using the cells for any high ouput/endurance applications, I'd
just like to have a visible indication of a cell's condition.
Relying upon a tester that includes a small load resistor and a meter
doesn't give any worthwhile indication of a cell's condition.

I have a charger/discharger made by MRC for the RC hobby, with fully
selectable settings for charging/discharging rates for up to 8 cells.
The MRC Super Brain 977 has a lot of features for battery packs, and a
test of condition related to discharging at 1/5th the capacity of a cell
or the entire pack. The user monitors the voltage as it drops.
http://www.modelrectifier.com/search...ew.asp?ID=1908

I'm not trying to restore/rejuvenate old, used, weak cells. I want to
build battery packs with high capacity cells (NiMH 4500mAh sub-C,
10000mAh D) for some of my low current demand) gear, so that one pack
will last for extended field use (a full day, not weeks) without needing
pack changes.
I'll use dedicated chargers for the different packs.

I use sophisticated smart chargers for my cordless tool battery packs,
and avoid using low quality chargers.

I have Sencore Z-meters but I don't think they'll give an ESR reading on
a charged cell.


See the effect of zapping
http://www.buchmann.ca/article23-page1.asp
There are many more examples of zapping new nicad cells online.
Recommended capacitor values and voltages differ greatly.
There are a lot of opinions online that are very dated, related to
battery types that were available years ago.

A trickle maintenance approach to eliminate self-discharging effect of
NiMH cells
http://www.ka7oei.com/nicds.html

--
Cheers,
WB
.............

Your statements are contradictory. For low current applications, the
ESR of the battery should be largely irrelevant...unless the cell is
dead, dead, dead.
Why do you need to zap cells to lower the ESR unless you're discharging
them VERY RAPIDLY?

I built a jig for sorting Lithium Ion cells for ESR at a junk dealer.
Just used a DVM to measure the voltage and a switch in series with
a light bulb to limit current from a eight-cell NiMH power supply.


Just read the volts, press the switch, read the volts again.
I needed the power pack because the cells were not charged.
If your cells are charged, you can just load the cell to ground.

I had good luck matching cells for building laptop battery packs.

A Tektronix 576 semiconductor curve tracer makes a great tool for
quickly evaluating ESR of cells.

A pulse generator and a scope will measure ESR. Just look at the
amplitude of the voltage step when you hit it with the known current
pulse. You can automate this to any degree you want with a sample-hold
and a microcontroller. If you use a square wave current, you can
measure the
P-P voltage at the cell and even plot it as a function of charge level.

I tried to do this with a GPIB programmable power supply. Problem
is that the battery voltage changes continuously when you turn on the
current. To get repeatable measurements, you need to accurately control
the time between turning on the current and reading the voltage.
I couldn't make this work with all the variable latencies
in the windows OS and the GPIB controller and the supply. My
light bulb scheme worked about as well in practice.

The guys who are fanatics about this reside in the model car racing
groups. But you have to do a lot of sifting. Many people have no idea
what they're doing and just post anecdotes of how they got 100A out of
a cell with no real verifiable
experimental results.

I believe that just because a battery cell test shows a full charge, doesn't
mean that the full charge can be gotten out of the cell (imbalance).

Checking ESR at random intervals could indicate if cells are unbalanced, I
think.
Charging at C/10 is said to balance cells, but how often? Having a means to
indicate (actually see) imbalance would give the user an idea of how often.

I prefer to test capacitor ESR and other parameters before I install them,
as there are always inconsistencies in manufacturing.
No, I don't routinely retest them at regular intervals after installation,
but when circuit performance is poor, ESR testing is generally the first
step.

The only reason I would want to zap nicad cells is to actually see if the
internal resistance is improved/lowered. I believe an ESR test would be a
good indication of any change that takes place.

Otherwise, an ESR test after cells have been used a while, may be a better
indication of it's condition, and possibly it's reliability.
I suspect that an unbalanced cell in a battery pack is bad for all the cells
in the pack, as it's likely to generate more heat, and possibly result in an
incomplete or overcharged state.

Your test fixture seems like a reasonable test, as a quick accept-or-reject
type of test.

I wouldn't want to automate tests, although it can be accomplished with the
right equipment and quite a bit of effort, by someone brighter than myself.
A dedicated analyzer/tester/reconditioner may be a better solution, but
costly.
I don't have to deal with so many batteries that a dedicated analyzer would
be practical.

I've seen a lot of inconsistent statements regarding battery maintenance and
performance.
One source that appears to be reliable is
http://www.buchmann.ca/default.asp

--
Cheers,
WB
..............


"mike" wrote in message
...
Wild_Bill wrote:
I've been doing a lot of reading wrt battery cell testing, but have only
seen one (affordable, reasonably priced) recommendation for testing
rechargeable cell ESR.. the Bob Parker ESR Meter.

http://www.flippers.com/esrkthnt.html (near the bottom)
http://www.prc68.com/I/BatTst.shtml#EVB


Your statements are contradictory. For low current applications, the
ESR of the battery should be largely irrelevant...unless the cell is dead,
dead, dead.
Why do you need to zap cells to lower the ESR unless you're discharging
them VERY RAPIDLY?

I built a jig for sorting Lithium Ion cells for ESR at a junk dealer.
Just used a DVM to measure the voltage and a switch in series with
a light bulb to limit current from a eight-cell NiMH power supply.


Just read the volts, press the switch, read the volts again.
I needed the power pack because the cells were not charged.
If your cells are charged, you can just load the cell to ground.

I had good luck matching cells for building laptop battery packs.

A Tektronix 576 semiconductor curve tracer makes a great tool for
quickly evaluating ESR of cells.

A pulse generator and a scope will measure ESR. Just look at the
amplitude of the voltage step when you hit it with the known current
pulse. You can automate this to any degree you want with a sample-hold
and a microcontroller. If you use a square wave current, you can measure
the
P-P voltage at the cell and even plot it as a function of charge level.

I tried to do this with a GPIB programmable power supply. Problem
is that the battery voltage changes continuously when you turn on the
current. To get repeatable measurements, you need to accurately control
the time between turning on the current and reading the voltage.
I couldn't make this work with all the variable latencies
in the windows OS and the GPIB controller and the supply. My
light bulb scheme worked about as well in practice.

The guys who are fanatics about this reside in the model car racing
groups. But you have to do a lot of sifting. Many people have no idea
what they're doing and just post anecdotes of how they got 100A out of
a cell with no real verifiable
experimental results.

On Fri, 15 Jan 2010 18:48:02 -0500, "Wild_Bill"
wrote:

I believe that just because a battery cell test shows a full charge, doesn't
mean that the full charge can be gotten out of the cell (imbalance).

Checking ESR at random intervals could indicate if cells are unbalanced, I
think.

I don't understand why you believe ESR and imbalance have any
relationship whatsoever.

Charging at C/10 is said to balance cells, but how often? Having a means to
indicate (actually see) imbalance would give the user an idea of how often.

Yes, BUT most charging regimes for NiXX chemistries are current-based
and overcharge the cells somewhat. This provides SOC balancing.

I prefer to test capacitor ESR and other parameters before I install them,
as there are always inconsistencies in manufacturing.

Do whatever you feel important. I wouldn't bother.

No, I don't routinely retest them at regular intervals after installation,
but when circuit performance is poor, ESR testing is generally the first
step.

Whose first step?

The only reason I would want to zap nicad cells is to actually see if the
internal resistance is improved/lowered. I believe an ESR test would be a
good indication of any change that takes place.

"zapping" NiCd cells will *only* (and then temporarily) remove
conductive dendrites. If the cells have dendrites then they are
already on their last legs, and should be discarded before they cause
you grief. If they don't have dendrites, *zapping" will achieve
nothing, but hey, whatever floats your boat.

Otherwise, an ESR test after cells have been used a while, may be a better
indication of it's condition, and possibly it's reliability.

ESR (or more correctly, internal resistance) tests on a healthy cell
will indicate maybe the extent of irreversible deterioration. To that
extent it may provide some useful information.

I suspect that an unbalanced cell in a battery pack is bad for all the cells
in the pack, as it's likely to generate more heat, and possibly result in an
incomplete or overcharged state.

Yes, but ESR and imbalance are unrelated.

Your test fixture seems like a reasonable test, as a quick accept-or-reject
type of test.

I wouldn't want to automate tests, although it can be accomplished with the
right equipment and quite a bit of effort, by someone brighter than myself.
A dedicated analyzer/tester/reconditioner may be a better solution, but
costly.
I don't have to deal with so many batteries that a dedicated analyzer would
be practical.

I've seen a lot of inconsistent statements regarding battery maintenance and
performance.
One source that appears to be reliable is
http://www.buchmann.ca/default.asp

Pffft!

The medium sized UPS gear we used (3x 300kVA/40minutes) had an
integrated real-time battery condition monitoring system. This simply
applied a known pulsed load to the battery systems (at multiple tap
points) and monitored the corresponding voltage steps, which gave a
direct indication of cell resistance. If any segment of a battery
string reached a threshold value, that string was taken out of service
and cell-by-cell testing was undertaken, follwed by any required
remedial action.

You could set up a similar tester for manual operation (similar to
mike's description) and gain useful insight into internal resistance.

"who where" wrote in message
news
On Fri, 15 Jan 2010 18:48:02 -0500, "Wild_Bill"
wrote:

I believe that just because a battery cell test shows a full charge,
doesn't
mean that the full charge can be gotten out of the cell (imbalance).

Checking ESR at random intervals could indicate if cells are unbalanced, I
think.

I don't understand why you believe ESR and imbalance have any
relationship whatsoever.
I don't presume to know.. internal resistance is a factor, maybe not the
most critical, but a parameter that could be useful. As I've said, I believe
ESR/IR is more useful than a simple battery test meter.
As the cell's IR increases, it's capacity drops, from what I've read.

Charging at C/10 is said to balance cells, but how often? Having a means
to
indicate (actually see) imbalance would give the user an idea of how
often.
Yes, BUT most charging regimes for NiXX chemistries are current-based
and overcharge the cells somewhat. This provides SOC balancing.
The info I've found indicates the opposite.. imbalance isn't improved by
continuing to recharge in the usual manner (the same charging techniques).
I believe that imbalance is related to a battery pack's longevity.

And since most battery users can't improve or modify their existing
chargers' behaviors, they're stuck with what they have.


I prefer to test capacitor ESR and other parameters before I install them,
as there are always inconsistencies in manufacturing.

Do whatever you feel important. I wouldn't bother.



No, I don't routinely retest them at regular intervals after installation,
but when circuit performance is poor, ESR testing is generally the first
step.

Whose first step?
I was referring to capacitors here, so ask anyone that regularly performs
service or repair work how important their ESR testers are.


The only reason I would want to zap nicad cells is to actually see if the
internal resistance is improved/lowered. I believe an ESR test would be a
good indication of any change that takes place.

"zapping" NiCd cells will *only* (and then temporarily) remove
conductive dendrites. If the cells have dendrites then they are
already on their last legs, and should be discarded before they cause
you grief. If they don't have dendrites, *zapping" will achieve
nothing, but hey, whatever floats your boat.

Battery manufacturers and serious users disagree.. they've proven that
zapping new, high quality Nicad cells increases output voltage levels and
lowers the ESR/IR.
The reported capacitor values and zapping voltages vary, so I don't think
there is an ultimate combination.

As I mentioned earlier, I'm not interested in trying to revive old, weak
cells.

Otherwise, an ESR test after cells have been used a while, may be a better
indication of it's condition, and possibly it's reliability.


ESR (or more correctly, internal resistance) tests on a healthy cell
will indicate maybe the extent of irreversible deterioration. To that
extent it may provide some useful information.


I suspect that an unbalanced cell in a battery pack is bad for all the
cells
in the pack, as it's likely to generate more heat, and possibly result in
an
incomplete or overcharged state.

Yes, but ESR and imbalance are unrelated.

I believe that battery industry professionals consider ESR/IR to be a
significant factor in cell construction and later for end-user performance.


I've seen a lot of inconsistent statements regarding battery maintenance
and
performance.
One source that appears to be reliable is
http://www.buchmann.ca/default.asp

Pffft!
http://www.batteryuniversity.com/
Essentially the same info, written by the founder/inventor of the Cadex
equipment. I'm not just referring to info found in an afternoon's browsing.
I've been examining battery info/data for several years. As I stated
earlier, I mostly disregard much of the info in the hobby-type forums that
appear to be written by inexperienced kids.
I'm able to spot reports that lack scientific perspective (just opinions
based upon voodoo techniques).
I suspect that much of the older info doesn't relate very well to today's
newer cells.

The medium sized UPS gear we used (3x 300kVA/40minutes) had an
integrated real-time battery condition monitoring system. This simply
applied a known pulsed load to the battery systems (at multiple tap
points) and monitored the corresponding voltage steps, which gave a
direct indication of cell resistance. If any segment of a battery
string reached a threshold value, that string was taken out of service
and cell-by-cell testing was undertaken, follwed by any required
remedial action.
I wonder what action. A series of recharge/discharge cycles and retesting?
Reconditioning in-house, or sent out?
For UPS duty, problem batteries should probably just be replaced. The
potential value of a failure could be enormous.

You could set up a similar tester for manual operation (similar to
mike's description) and gain useful insight into internal resistance.
A light bulb and DVM tester could be a handy gage for initial checks.

My reason for asking about utilizing an ESR tester was because ESR testers
display an ESR reading, and readings are easily compared. The ESR tester
could likely be used on battery packs regardless of the pack's SOC state of
charge.

As Phil A pointed out, the Bob Parker ESR meter could be useful for battery
packs, but I may need to find my milliohm meter to try on individual cells,
if it's capable.

A poor IR reading on a new cell (compared to the other new cells from the
same purchase) would be something that I'd want to be aware of.

--
Cheers,
WB
..............

On Sat, 16 Jan 2010 08:06:06 -0500, "Wild_Bill"
wrote:


"who where" wrote in message
news
On Fri, 15 Jan 2010 18:48:02 -0500, "Wild_Bill"
wrote:

I believe that just because a battery cell test shows a full charge,
doesn't
mean that the full charge can be gotten out of the cell (imbalance).

Checking ESR at random intervals could indicate if cells are unbalanced, I
think.

I don't understand why you believe ESR and imbalance have any
relationship whatsoever.

I don't presume to know.. internal resistance is a factor, maybe not the
most critical, but a parameter that could be useful. As I've said, I believe
ESR/IR is more useful than a simple battery test meter.
As the cell's IR increases, it's capacity drops, from what I've read.

No. Note TWO relationships: (1) Internal resistance will have an
effect on the usable capacity, in that it will result in earlier
discharge termination at the terminal voltage will droop more under
load. (2) As the cell's usable capacity reduces due to "wear and
tear", the internal resistance will usually rise for similar reasons.
But IR is NOT the cause of reduced capacity.

Charging at C/10 is said to balance cells, but how often? Having a means
to
indicate (actually see) imbalance would give the user an idea of how
often.
Yes, BUT most charging regimes for NiXX chemistries are current-based
and overcharge the cells somewhat. This provides SOC balancing.

The info I've found indicates the opposite.

Well you can't have it both ways. About 8 lines above, you state that
"Charging at C/10 is said to balance cells". Pick one.

imbalance isn't improved by continuing to recharge in the usual manner (the same charging techniques).

First let's be clear that we are talking about SERIES-connected cells.
When exposed to charging current cells will recharge. If cells in a
series string have a different SOC at the commencement of recharge,
the *normal* (i.e. over-) charging regimes - including the "C/10 for
14 hours" - will ensure that the cells with lower SOC are dragged
closer to the SOC of the others. This may or may not take more than
one charge cycle, but it will happen.

What this means in terms of cells with different usable capacities (as
distinct from different internal resistances) isn't a real issue.
Discharge is another story.

I believe that imbalance is related to a battery pack's longevity.

It certainly can/does lead to cell reversal under deep discharge,
which can damage a pack.

And since most battery users can't improve or modify their existing
chargers' behaviors, they're stuck with what they have.

Agreed. We disagree though on what that means.

I prefer to test capacitor ESR and other parameters before I install them,
as there are always inconsistencies in manufacturing.

Do whatever you feel important. I wouldn't bother.

No, I don't routinely retest them at regular intervals after installation,
but when circuit performance is poor, ESR testing is generally the first
step.

Whose first step?

I was referring to capacitors here

OK, my error.

so ask anyone that regularly performs
service or repair work how important their ESR testers are.

I use my ESR meter frequently, but extremely rarely on anything except
electrolytic caps..

The only reason I would want to zap nicad cells is to actually see if the
internal resistance is improved/lowered. I believe an ESR test would be a
good indication of any change that takes place.

"zapping" NiCd cells will *only* (and then temporarily) remove
conductive dendrites. If the cells have dendrites then they are
already on their last legs, and should be discarded before they cause
you grief. If they don't have dendrites, *zapping" will achieve
nothing, but hey, whatever floats your boat.

Battery manufacturers and serious users disagree.. they've proven that
zapping new, high quality Nicad cells increases output voltage levels and
lowers the ESR/IR.

If battery manufacturers beleived that, they'd all be doing it
routinely before shipping their product.

The reported capacitor values and zapping voltages vary, so I don't think
there is an ultimate combination.

I believe it is just more snake oil, but ....

As I mentioned earlier, I'm not interested in trying to revive old, weak
cells.

Otherwise, an ESR test after cells have been used a while, may be a better
indication of it's condition, and possibly it's reliability.


ESR (or more correctly, internal resistance) tests on a healthy cell
will indicate maybe the extent of irreversible deterioration. To that
extent it may provide some useful information.


I suspect that an unbalanced cell in a battery pack is bad for all the
cells
in the pack, as it's likely to generate more heat, and possibly result in
an
incomplete or overcharged state.

Yes, but ESR and imbalance are unrelated.

I believe that battery industry professionals consider ESR/IR to be a
significant factor in cell construction and later for end-user performance.

You *believe* that "they consider"? Hmmm?

I've seen a lot of inconsistent statements regarding battery maintenance
and performance.
One source that appears to be reliable is
http://www.buchmann.ca/default.asp

Pffft!
http://www.batteryuniversity.com/
Essentially the same info, written by the founder/inventor of the Cadex
equipment. I'm not just referring to info found in an afternoon's browsing.
I've been examining battery info/data for several years. As I stated
earlier, I mostly disregard much of the info in the hobby-type forums that
appear to be written by inexperienced kids.
I'm able to spot reports that lack scientific perspective (just opinions
based upon voodoo techniques).
I suspect that much of the older info doesn't relate very well to today's
newer cells.

The medium sized UPS gear we used (3x 300kVA/40minutes) had an
integrated real-time battery condition monitoring system. This simply
applied a known pulsed load to the battery systems (at multiple tap
points) and monitored the corresponding voltage steps, which gave a
direct indication of cell resistance. If any segment of a battery
string reached a threshold value, that string was taken out of service
and cell-by-cell testing was undertaken, follwed by any required
remedial action.

I wonder what action. A series of recharge/discharge cycles and retesting?
Reconditioning in-house, or sent out?

Replacement.

For UPS duty, problem batteries should probably just be replaced. The
potential value of a failure could be enormous.

Exactly. Without being specific, the fact that we had 3x 300kVA units
would suggest that our operation and its continuity were considered
more important than the cost of replacment cells. And before you ask,
suspect cells were replaced individually based on these tests, and
when the number of replacements reached a certain percentage of the
string the whole string was replaced.

You could set up a similar tester for manual operation (similar to
mike's description) and gain useful insight into internal resistance.
A light bulb and DVM tester could be a handy gage for initial checks.

My reason for asking about utilizing an ESR tester was because ESR testers
display an ESR reading, and readings are easily compared. The ESR tester
could likely be used on battery packs regardless of the pack's SOC state of
charge.

As Phil A pointed out, the Bob Parker ESR meter could be useful for battery
packs

yup

but I may need to find my milliohm meter to try on individual cells,
if it's capable.

A "normal" (milli-)ohm meter wont give you any useful indication from
a charged cell except maybe smoke signals. The Bob Parker ESR meter
(I use one) uses an AC excitation and measures the voltage across the
target device that results, effectively removing the DC component
which will generally smoke your ohm-meter

A poor IR reading on a new cell (compared to the other new cells from the
same purchase) would be something that I'd want to be aware of.

Indeed.

"who where"
"Wild_Bill"


I don't presume to know.. internal resistance is a factor, maybe not the
most critical, but a parameter that could be useful. As I've said, I
believe
ESR/IR is more useful than a simple battery test meter.
As the cell's IR increases, it's capacity drops, from what I've read.

No. Note TWO relationships: (1) Internal resistance will have an
effect on the usable capacity, in that it will result in earlier
discharge termination at the terminal voltage will droop more under
load. (2) As the cell's usable capacity reduces due to "wear and
tear", the internal resistance will usually rise for similar reasons.
But IR is NOT the cause of reduced capacity.

** Bill's post does not say it was - only that there is a correlation.

There is a strong correlation between measured ESR and state of charge for
non-rechargeable cells - but it is only when a NiCd or NiMH cell is almost
completely discharged that the ESR rises.

The whole idea is that ESR testing is a COMPARATIVE measurement applied to
a *number of cells* that are of the same type and with a similar history to
see if any show higher readings than the others.

It is also useful to apply ESR testing to a pack of cells and see if the
total ESR is any more than slightly over the typical ESR of each cell
multiplied by the number of cells. A higher than expected reading indicates
one or more bad cells or possibly high resistance spot welds inside the
pack.

It can take hours to do a charge and discharge tests on a packs of cells -
but only SECONDS to do an ESR test on a pack and find immediately that no
further testing is warranted.



..... Phil

who where wrote:
On Sat, 16 Jan 2010 08:06:06 -0500, "Wild_Bill"
wrote:

"who where" wrote in message
news
On Fri, 15 Jan 2010 18:48:02 -0500, "Wild_Bill"
wrote:

I believe that just because a battery cell test shows a full charge,
doesn't
mean that the full charge can be gotten out of the cell (imbalance).

Checking ESR at random intervals could indicate if cells are unbalanced, I
think.
I don't understand why you believe ESR and imbalance have any
relationship whatsoever.

I don't presume to know.. internal resistance is a factor, maybe not the
most critical, but a parameter that could be useful. As I've said, I believe
ESR/IR is more useful than a simple battery test meter.
As the cell's IR increases, it's capacity drops, from what I've read.

No. Note TWO relationships: (1) Internal resistance will have an
effect on the usable capacity, in that it will result in earlier
discharge termination at the terminal voltage will droop more under
load. (2) As the cell's usable capacity reduces due to "wear and
tear", the internal resistance will usually rise for similar reasons.
But IR is NOT the cause of reduced capacity.

Charging at C/10 is said to balance cells, but how often? Having a means
to
indicate (actually see) imbalance would give the user an idea of how
often.
Yes, BUT most charging regimes for NiXX chemistries are current-based
and overcharge the cells somewhat. This provides SOC balancing.

The info I've found indicates the opposite.

Well you can't have it both ways. About 8 lines above, you state that
"Charging at C/10 is said to balance cells". Pick one.

imbalance isn't improved by continuing to recharge in the usual manner (the same charging techniques).

First let's be clear that we are talking about SERIES-connected cells.
When exposed to charging current cells will recharge. If cells in a
series string have a different SOC at the commencement of recharge,
the *normal* (i.e. over-) charging regimes - including the "C/10 for
14 hours" - will ensure that the cells with lower SOC are dragged
closer to the SOC of the others. This may or may not take more than
one charge cycle, but it will happen.

What this means in terms of cells with different usable capacities (as
distinct from different internal resistances) isn't a real issue.
Discharge is another story.

I believe that imbalance is related to a battery pack's longevity.

It certainly can/does lead to cell reversal under deep discharge,
which can damage a pack.

And since most battery users can't improve or modify their existing
chargers' behaviors, they're stuck with what they have.

Agreed. We disagree though on what that means.

I prefer to test capacitor ESR and other parameters before I install them,
as there are always inconsistencies in manufacturing.
Do whatever you feel important. I wouldn't bother.
No, I don't routinely retest them at regular intervals after installation,
but when circuit performance is poor, ESR testing is generally the first
step.
Whose first step?

I was referring to capacitors here

OK, my error.

so ask anyone that regularly performs
service or repair work how important their ESR testers are.

I use my ESR meter frequently, but extremely rarely on anything except
electrolytic caps..

The only reason I would want to zap nicad cells is to actually see if the
internal resistance is improved/lowered. I believe an ESR test would be a
good indication of any change that takes place.
"zapping" NiCd cells will *only* (and then temporarily) remove
conductive dendrites. If the cells have dendrites then they are
already on their last legs, and should be discarded before they cause
you grief. If they don't have dendrites, *zapping" will achieve
nothing, but hey, whatever floats your boat.

Battery manufacturers and serious users disagree.. they've proven that
zapping new, high quality Nicad cells increases output voltage levels and
lowers the ESR/IR.



If battery manufacturers beleived that, they'd all be doing it
routinely before shipping their product.

It may not be as simple as that. Battery manufacturers are interested
in profit, quality, reputation etc. It may be that one parameter can
be improved by sacrificing another to an unacceptable degree.

It's possible that zapping might lower esr temporarily but result in
overall reduction in performance over the life of the cells.

The zapping info seems to come from model car/plane racers. They're
interested
in ONE thing...winning the race. They don't give a rats ass whether
they get 300 discharge cycles out of the battery.

Preoccupation with one parameter like esr/ir may not result in maximum
uptime for your servers or lowest overall operating cost.


The reported capacitor values and zapping voltages vary, so I don't think
there is an ultimate combination.

I believe it is just more snake oil, but ....

As I mentioned earlier, I'm not interested in trying to revive old, weak
cells.

Otherwise, an ESR test after cells have been used a while, may be a better
indication of it's condition, and possibly it's reliability.
ESR (or more correctly, internal resistance) tests on a healthy cell
will indicate maybe the extent of irreversible deterioration. To that
extent it may provide some useful information.

I suspect that an unbalanced cell in a battery pack is bad for all the
cells
in the pack, as it's likely to generate more heat, and possibly result in
an
incomplete or overcharged state.
Yes, but ESR and imbalance are unrelated.

I believe that battery industry professionals consider ESR/IR to be a
significant factor in cell construction and later for end-user performance.

You *believe* that "they consider"? Hmmm?

I've seen a lot of inconsistent statements regarding battery maintenance
and performance.
One source that appears to be reliable is
http://www.buchmann.ca/default.asp
Pffft!
http://www.batteryuniversity.com/
Essentially the same info, written by the founder/inventor of the Cadex
equipment. I'm not just referring to info found in an afternoon's browsing.
I've been examining battery info/data for several years. As I stated
earlier, I mostly disregard much of the info in the hobby-type forums that
appear to be written by inexperienced kids.
I'm able to spot reports that lack scientific perspective (just opinions
based upon voodoo techniques).
I suspect that much of the older info doesn't relate very well to today's
newer cells.

The medium sized UPS gear we used (3x 300kVA/40minutes) had an
integrated real-time battery condition monitoring system. This simply
applied a known pulsed load to the battery systems (at multiple tap
points) and monitored the corresponding voltage steps, which gave a
direct indication of cell resistance. If any segment of a battery
string reached a threshold value, that string was taken out of service
and cell-by-cell testing was undertaken, follwed by any required
remedial action.

I wonder what action. A series of recharge/discharge cycles and retesting?
Reconditioning in-house, or sent out?

Replacement.

For UPS duty, problem batteries should probably just be replaced. The
potential value of a failure could be enormous.

Exactly. Without being specific, the fact that we had 3x 300kVA units
would suggest that our operation and its continuity were considered
more important than the cost of replacment cells. And before you ask,
suspect cells were replaced individually based on these tests, and
when the number of replacements reached a certain percentage of the
string the whole string was replaced.

You could set up a similar tester for manual operation (similar to
mike's description) and gain useful insight into internal resistance.
A light bulb and DVM tester could be a handy gage for initial checks.

My reason for asking about utilizing an ESR tester was because ESR testers
display an ESR reading, and readings are easily compared. The ESR tester
could likely be used on battery packs regardless of the pack's SOC state of
charge.

As Phil A pointed out, the Bob Parker ESR meter could be useful for battery
packs

yup

but I may need to find my milliohm meter to try on individual cells,
if it's capable.

A "normal" (milli-)ohm meter wont give you any useful indication from
a charged cell except maybe smoke signals. The Bob Parker ESR meter
(I use one) uses an AC excitation and measures the voltage across the
target device that results, effectively removing the DC component
which will generally smoke your ohm-meter

A poor IR reading on a new cell (compared to the other new cells from the
same purchase) would be something that I'd want to be aware of.

Indeed.

On Sat, 16 Jan 2010 19:49:24 -0800, mike wrote:

who where wrote:
On Sat, 16 Jan 2010 08:06:06 -0500, "Wild_Bill"
wrote:
(snip)
Battery manufacturers and serious users disagree.. they've proven that
zapping new, high quality Nicad cells increases output voltage levels and
lowers the ESR/IR.

If battery manufacturers beleived that, they'd all be doing it
routinely before shipping their product.

It may not be as simple as that. Battery manufacturers are interested
in profit, quality, reputation etc. It may be that one parameter can
be improved by sacrificing another to an unacceptable degree.

It's possible that zapping might lower esr temporarily but result in
overall reduction in performance over the life of the cells.

That's exactly what I believe to be the case, *if* zapping at birth
has any effect at all.

The zapping info seems to come from model car/plane racers. They're
interested
in ONE thing...winning the race. They don't give a rats ass whether
they get 300 discharge cycles out of the battery.

yup

Preoccupation with one parameter like esr/ir may not result in maximum
uptime for your servers or lowest overall operating cost.

On Fri, 15 Jan 2010 18:48:02 -0500, "Wild_Bill"
wrote:

One source that appears to be reliable is
http://www.buchmann.ca/default.asp

That's Isidor Buchmann's (Cadex) site and runs kinda slow. The public
info is at:
http://www.batteryuniversity.com
I agree. It's the best battery reference I can find.

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