Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work.

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Old May 19th 17, 05:33 PM posted to rec.crafts.metalworking
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Default Battery capacity testing

I've finally acquired enough equipment to measure the remaining
Amp-Hour capacity of my Lead-Acid and Lithium battery collection. The
first result that jumped out is that older batteries suffer from
rising internal resistance as they discharge, enough that the
automatic low voltage cutoff trips short of rated capacity, and then
the battery slowly recovers to well above the full discharge voltage
given in the specs.

http://www.power-sonic.com/images/po...hManual-Lo.pdf

The 5-year-old 12v 4.5Ah UPS battery I tested this AM delivered 2.45Ah
at 3A, which is the average current my laptop draws while browsing.
Table 2 shows in the 1 Hour Rate column that it should be good for
2.75Ah at 2.75A current.

Does anyone know a good reason why I can't measure the true remaining
capacity in two steps by first discharging to 10V at the fairly high
current of my typical loads, then continuing at the 20 hour rate AGM
batteries are specified for until the voltage drops to [the
appropriate endpoint] again?

The run time for a typical load tells me how useful the battery still
is, but it combines the effects of capacity and resistance. I'm
wondering if also knowing the Amp-Hour capacity at the 20 hour rate,
with less interference from the internal resistance, would indicate
how well my long-term maintenance procedures work.

-jsw



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Old May 19th 17, 05:51 PM posted to rec.crafts.metalworking
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Default Battery capacity testing

"Jim Wilkins" wrote in message
news

The 5-year-old 12v 4.5Ah UPS battery I tested this AM delivered
2.45Ah at 3A, which is the average current my laptop draws while
browsing. Table 2 shows in the 1 Hour Rate column that it should be
good for 2.75Ah at 2.75A current.

-jsw


That wasn't a good example. I have a 12V 12Ah AGM battery that is down
to 1 useful Amp-hour because its voltage droops to 10V so quickly.
Afterwards it recovers above 12.2V.
-jsw


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Old May 19th 17, 07:26 PM posted to rec.crafts.metalworking
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Default Battery capacity testing

On Friday, May 19, 2017 at 12:33:52 PM UTC-4, Jim Wilkins wrote:
I've finally acquired enough equipment to measure the remaining
Amp-Hour capacity of my Lead-Acid and Lithium battery collection. The
first result that jumped out is that older batteries suffer from
rising internal resistance as they discharge, enough that the
automatic low voltage cutoff trips short of rated capacity, and then
the battery slowly recovers to well above the full discharge voltage
given in the specs.

http://www.power-sonic.com/images/po...hManual-Lo.pdf

The 5-year-old 12v 4.5Ah UPS battery I tested this AM delivered 2.45Ah
at 3A, which is the average current my laptop draws while browsing.
Table 2 shows in the 1 Hour Rate column that it should be good for
2.75Ah at 2.75A current.

Does anyone know a good reason why I can't measure the true remaining
capacity in two steps by first discharging to 10V at the fairly high
current of my typical loads, then continuing at the 20 hour rate AGM
batteries are specified for until the voltage drops to [the
appropriate endpoint] again?

The run time for a typical load tells me how useful the battery still
is, but it combines the effects of capacity and resistance. I'm
wondering if also knowing the Amp-Hour capacity at the 20 hour rate,
with less interference from the internal resistance, would indicate
how well my long-term maintenance procedures work.

-jsw


I think that doing the 20 hour test my provide you with academic indication of the condition of the batteries, but only at the 20 hour rate. In my recollection (based on 25 years ago designing a 100 station lead acid charger), there is surprisingly little correlation between capacity at different discharge rates.

So, I would suggest you test at your normal load and perhaps with a "normal minimum load" assuming that those rates are pretty far from 20 hours. Anything else is, as I said, purely academic.

BTW, while I was buying the voltage reference, I also bought a USB power meter (Drok). The Amazon add and the user's manual keep referring to "capacitance" measurement. What they really mean is capacity of USB battery packs. Pretty funny. Sort of. You can actually buy this meter bundled with a USB load bank.
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Old May 19th 17, 09:13 PM posted to rec.crafts.metalworking
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Posts: 4,798
Default Battery capacity testing


"rangerssuck" wrote in message
...
On Friday, May 19, 2017 at 12:33:52 PM UTC-4, Jim Wilkins wrote:
I've finally acquired enough equipment to measure the remaining
Amp-Hour capacity of my Lead-Acid and Lithium battery collection.
The
first result that jumped out is that older batteries suffer from
rising internal resistance as they discharge, enough that the
automatic low voltage cutoff trips short of rated capacity, and then
the battery slowly recovers to well above the full discharge voltage
given in the specs.

http://www.power-sonic.com/images/po...hManual-Lo.pdf

The 5-year-old 12v 4.5Ah UPS battery I tested this AM delivered
2.45Ah
at 3A, which is the average current my laptop draws while browsing.
Table 2 shows in the 1 Hour Rate column that it should be good for
2.75Ah at 2.75A current.

Does anyone know a good reason why I can't measure the true
remaining
capacity in two steps by first discharging to 10V at the fairly high
current of my typical loads, then continuing at the 20 hour rate AGM
batteries are specified for until the voltage drops to [the
appropriate endpoint] again?

The run time for a typical load tells me how useful the battery
still
is, but it combines the effects of capacity and resistance. I'm
wondering if also knowing the Amp-Hour capacity at the 20 hour rate,
with less interference from the internal resistance, would indicate
how well my long-term maintenance procedures work.

-jsw


I think that doing the 20 hour test my provide you with academic
indication of the condition of the batteries, but only at the 20 hour
rate. In my recollection (based on 25 years ago designing a 100
station lead acid charger), there is surprisingly little correlation
between capacity at different discharge rates.

So, I would suggest you test at your normal load and perhaps with a
"normal minimum load" assuming that those rates are pretty far from 20
hours. Anything else is, as I said, purely academic.

BTW, while I was buying the voltage reference, I also bought a USB
power meter (Drok). The Amazon add and the user's manual keep
referring to "capacitance" measurement. What they really mean is
capacity of USB battery packs. Pretty funny. Sort of. You can actually
buy this meter bundled with a USB load bank.

=========================

I want to separate the effects of capacity and internal resistance to
see if equalizing etc improves either or both of them. The internal
resistance of AGMs has some strangely behaved component reputedly
related to an oxide film. Otherwise I discharge them at the current my
laptop draws when browsing as I have them for power-outage backup and
NWS radar is the best indication of storms approaching my house that
I've found. It tells me when to repair roof damage and when to tarp
it.

I bought this which has an easily set low voltage disconnect and
handles up to +/-30A,
https://www.amazon.com/DROK-Display-...ct_top?ie=UTF8

and previously this which is 10x as accurate at low current
https://www.amazon.com/bayite-Multif.../dp/B01D7JGGE4

The first one measures charge and discharge current separately and
counts the Amp-hours up or down accordingly, though the Watt-hours
total is the positive sum of both (???). It has a more accurate
voltmeter and a better timer that counts seconds and stops when the
relay opens, allowing a pause in the measurement and a record of
battery run time. Unfortunately the current resolution is 0.1A despite
the display, so it doesn't handle small AGMs well.

The second one matches other ammeters to 1 or 2 digits and I use both
in series for discharge loads up to 10A. Together they each make up
for the deficiencies of the other. The 12V,12Ah battery is discharging
on them at 0.5A.
-jsw


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Old May 19th 17, 10:43 PM posted to rec.crafts.metalworking
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First recorded activity by DIYBanter: Jun 2011
Posts: 4,798
Default Battery capacity testing

"Jim Wilkins" wrote in message
news

"rangerssuck" wrote in message
...
I think that doing the 20 hour test my provide you with academic
indication of the condition of the batteries, but only at the 20
hour rate. In my recollection (based on 25 years ago designing a 100
station lead acid charger), there is surprisingly little correlation
between capacity at different discharge rates.


I've read that repeated capacity tests on the same battery don't
correlate well.





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Old May 19th 17, 11:55 PM posted to rec.crafts.metalworking
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First recorded activity by DIYBanter: Oct 2012
Posts: 1,086
Default Battery capacity testing

On 5/19/2017 9:33 AM, Jim Wilkins wrote:
I've finally acquired enough equipment to measure the remaining
Amp-Hour capacity of my Lead-Acid and Lithium battery collection. The
first result that jumped out is that older batteries suffer from
rising internal resistance as they discharge, enough that the
automatic low voltage cutoff trips short of rated capacity, and then
the battery slowly recovers to well above the full discharge voltage
given in the specs.

http://www.power-sonic.com/images/po...hManual-Lo.pdf

The 5-year-old 12v 4.5Ah UPS battery I tested this AM delivered 2.45Ah
at 3A, which is the average current my laptop draws while browsing.
Table 2 shows in the 1 Hour Rate column that it should be good for
2.75Ah at 2.75A current.

Does anyone know a good reason why I can't measure the true remaining
capacity in two steps by first discharging to 10V at the fairly high
current of my typical loads, then continuing at the 20 hour rate AGM
batteries are specified for until the voltage drops to [the
appropriate endpoint] again?

The run time for a typical load tells me how useful the battery still
is, but it combines the effects of capacity and resistance. I'm
wondering if also knowing the Amp-Hour capacity at the 20 hour rate,
with less interference from the internal resistance, would indicate
how well my long-term maintenance procedures work.

-jsw


I gave up. Never got any predictive information.

Most of my testing was done with Lithium batteries in laptops.

I consider a laptop battery bad when it won't run the laptop
long enough. How vague is that? ;-)

Started with bad battery packs and tested cells.
At low current, I almost always got something like specified
capacity. The electrons are in there, but the laptop won't
let you have them.

I don't know what the sampling interval is, but the laptop
wants to shut down at some voltage so you don't lose data
and call the vendor. Subtract the peak voltage across the ESR
from the battery voltage. If it dips below the threshold,
the laptop wants to shut down.

Turn off the power features that warn of impending low voltage
shutdown.

The symptom is that the battery gauge decays slowly for a while
then drops instantly to a much lower number. The laptop senses
impending doom, but you've blocked that.
I've had laptops run two hours past the point when the battery
gauge hit zero. Problem is that when it dies, you lose whatever
you were working on.

I've never had any success trying to fix the ESR. That's probably
the same problem you have when your car fails to start. Never been
able to do anything about that either.

The higher the peak current, the fewer electrons all those
protection circuits will let you have.
Even with a new battery, capacity is a strong function of
load current.

Numbers from browsing the web won't help much when
Microsoft decides to do an update and runs all your cores
at 100%.
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Old May 20th 17, 01:31 AM posted to rec.crafts.metalworking
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Posts: 2,505
Default Battery capacity testing

On 2017-05-19, mike wrote:
On 5/19/2017 9:33 AM, Jim Wilkins wrote:
I've finally acquired enough equipment to measure the remaining
Amp-Hour capacity of my Lead-Acid and Lithium battery collection. The
first result that jumped out is that older batteries suffer from
rising internal resistance as they discharge, enough that the
automatic low voltage cutoff trips short of rated capacity, and then
the battery slowly recovers to well above the full discharge voltage
given in the specs.


[ ... ]

The higher the peak current, the fewer electrons all those
protection circuits will let you have.
Even with a new battery, capacity is a strong function of
load current.

Numbers from browsing the web won't help much when
Microsoft decides to do an update and runs all your cores
at 100%.


Well ... that is not a problem for me. The first thing I do
when I pick up a new (to me) laptop is to remove the virus. The last
virus was called "Windows 10". I replace it with either a linux or an
OpenBSD system, so Microsoft doesn't have a say in when I update, and
updates for the others are based on telling me that updates are
available, and letting me decide whether and when to install them. :-)

Enjoy,
DoN.

--
Remove oil spill source from e-mail
Email: | (KV4PH) Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---
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Old May 20th 17, 02:52 AM posted to rec.crafts.metalworking
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Posts: 4,798
Default Battery capacity testing

"mike" wrote in message
news
On 5/19/2017 9:33 AM, Jim Wilkins wrote:
...
The symptom is that the battery gauge decays slowly for a while
then drops instantly to a much lower number. The laptop senses
impending doom, but you've blocked that.
I've had laptops run two hours past the point when the battery
gauge hit zero. Problem is that when it dies, you lose whatever
you were working on.
...


The "fuel gauge" IC counts Coulombs in and out to determine actual
Lithium battery capacity, on the assumption that they recharge at 100%
efficiency. It resets its capacity estimate if the battery is nearly
fully discharged and recharged, but if only partly discharged it can't
detect the slow loss of capacity with age and retains the old, overly
optimistic number from the last full cycle. That's why the sudden jump
when it realizes it's wrong.

When you give the battery another full cycle it can measure and update
the battery capacity to its new, lower value.

As an experiment I reduced the low voltage trip as far as possible and
got almost as much run time from an old Dell battery below the 5%
level as from 100% to 5%. It appears that Li-Ion cells can be
discharged down to or even below 2.7V briefly without much damage. The
normal settings are above 3.0V.
http://batteryuniversity.com/learn/a...oltage_cut_off

This gives you the battery voltage:
https://www.hwinfo.com/

-jsw


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Old May 21st 17, 07:44 PM posted to rec.crafts.metalworking
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Default Battery capacity testing

On Fri, 19 May 2017 16:13:34 -0400, "Jim Wilkins"
wrote:


"rangerssuck" wrote in message
...
On Friday, May 19, 2017 at 12:33:52 PM UTC-4, Jim Wilkins wrote:
I've finally acquired enough equipment to measure the remaining
Amp-Hour capacity of my Lead-Acid and Lithium battery collection.
The
first result that jumped out is that older batteries suffer from
rising internal resistance as they discharge, enough that the
automatic low voltage cutoff trips short of rated capacity, and then
the battery slowly recovers to well above the full discharge voltage
given in the specs.

http://www.power-sonic.com/images/po...hManual-Lo.pdf

The 5-year-old 12v 4.5Ah UPS battery I tested this AM delivered
2.45Ah
at 3A, which is the average current my laptop draws while browsing.
Table 2 shows in the 1 Hour Rate column that it should be good for
2.75Ah at 2.75A current.

Does anyone know a good reason why I can't measure the true
remaining
capacity in two steps by first discharging to 10V at the fairly high
current of my typical loads, then continuing at the 20 hour rate AGM
batteries are specified for until the voltage drops to [the
appropriate endpoint] again?

The run time for a typical load tells me how useful the battery
still
is, but it combines the effects of capacity and resistance. I'm
wondering if also knowing the Amp-Hour capacity at the 20 hour rate,
with less interference from the internal resistance, would indicate
how well my long-term maintenance procedures work.

-jsw


I think that doing the 20 hour test my provide you with academic
indication of the condition of the batteries, but only at the 20 hour
rate. In my recollection (based on 25 years ago designing a 100
station lead acid charger), there is surprisingly little correlation
between capacity at different discharge rates.

So, I would suggest you test at your normal load and perhaps with a
"normal minimum load" assuming that those rates are pretty far from 20
hours. Anything else is, as I said, purely academic.

BTW, while I was buying the voltage reference, I also bought a USB
power meter (Drok). The Amazon add and the user's manual keep
referring to "capacitance" measurement. What they really mean is
capacity of USB battery packs. Pretty funny. Sort of. You can actually
buy this meter bundled with a USB load bank.

=========================

I want to separate the effects of capacity and internal resistance to
see if equalizing etc improves either or both of them. The internal
resistance of AGMs has some strangely behaved component reputedly
related to an oxide film. Otherwise I discharge them at the current my
laptop draws when browsing as I have them for power-outage backup and
NWS radar is the best indication of storms approaching my house that
I've found. It tells me when to repair roof damage and when to tarp
it.

I bought this which has an easily set low voltage disconnect and
handles up to +/-30A,
https://www.amazon.com/DROK-Display-...ct_top?ie=UTF8


Hmm, there are 3 different pictures of the back of those. One has a
built-in shunt, another a pair of relays, and another is bare. Which
is the real meter pic for the "30a w/ relay"?


and previously this which is 10x as accurate at low current
https://www.amazon.com/bayite-Multif.../dp/B01D7JGGE4


IF I ever get the weeding done around here, I'll get those panels up
and build the control panel to see how those li'l Bayites work.
You showed another link for a milliamp/millivolt-resolution meter a
few weeks ago, too. How's that working for you?


The first one measures charge and discharge current separately and
counts the Amp-hours up or down accordingly, though the Watt-hours
total is the positive sum of both (???). It has a more accurate
voltmeter and a better timer that counts seconds and stops when the
relay opens, allowing a pause in the measurement and a record of
battery run time. Unfortunately the current resolution is 0.1A despite
the display, so it doesn't handle small AGMs well.


The former part is cool. Not having proper resolution for decent data
is never fun, though.


The second one matches other ammeters to 1 or 2 digits and I use both
in series for discharge loads up to 10A. Together they each make up
for the deficiencies of the other. The 12V,12Ah battery is discharging
on them at 0.5A.


Did I ever ask you why you didn't use a real battery for that? g
(real being 12v 35-275Ah) I set one up for use with the 45w HF trio
of panels and was able to power a 14" electric chainsaw with the 2kW
modified sine wave inverter, also from HF. It would have taken days
to recharge it (or more panels if needed for continued use.)

--
In today’s academia and mainstream media,
we’re all guilty of hate until proven leftist.

--Robert Knight, senior fellow, American Civil Rights Union
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Old May 22nd 17, 12:49 AM posted to rec.crafts.metalworking
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Default Battery capacity testing

"Larry Jaques" wrote in message
news
On Fri, 19 May 2017 16:13:34 -0400, "Jim Wilkins"
wrote:

....................

I bought this which has an easily set low voltage disconnect and
handles up to +/-30A,
https://www.amazon.com/DROK-Display-...ct_top?ie=UTF8


Hmm, there are 3 different pictures of the back of those. One has a
built-in shunt, another a pair of relays, and another is bare.
Which
is the real meter pic for the "30a w/ relay"?


The 30A model I received has a shunt and blue NC relay on the base
module. The display module has a small red+black pigtail for external
power if you don't use a USB connection. At first the USB connection
on mine was poor and it intermittently shut off, or switched to
wireless without losing power. The correct accumulated totals
reappeared when it reconnected.

It displays current to 2 decimal places but is accurate only to 1
place +/-, for example 0.478A on a Fluke 8600A reads as 0.48A on the
10A "Electrical Parameter Tester", and 0.65A on the 30A unit.

A layer of Gorilla tape tightened the USB plug in the base unit
against the circuit board contacts and it has remained connected when
moved.

You showed another link for a milliamp/millivolt-resolution meter a
few weeks ago, too. How's that working for you?


The 33.00V/3.000A meter is my favorite for recharging and equalizing
batteries slowly from my solar panels. It clearly shows when a small
AGM's charging current has decreased to 1% of the C/20 capacity, like
45mA for a 4.5A-h AGM battery. Currents around 1% are recommended end
points for trickle charging.
http://www.trojanbattery.com/pdf/Tro...UsersGuide.pdf
Diagram 4 gives 1-3% for flooded, Diagram 5 gives 0.5% for AGM.

As mentioned, the current rises in older batteries and is an indicator
of declining condition.

The first one measures charge and discharge current separately and
counts the Amp-hours up or down accordingly, though the Watt-hours
total is the positive sum of both (???). It has a more accurate
voltmeter and a better timer that counts seconds and stops when the
relay opens, allowing a pause in the measurement and a record of
battery run time. Unfortunately the current resolution is 0.1A
despite
the display, so it doesn't handle small AGMs well.


The former part is cool. Not having proper resolution for decent
data
is never fun, though.


I first learned how to make accurate measurements as a chemist whose
results might have to stand up in court, then when building very
precise automatic test equipment for the semiconductor industry.
Analog Devices' op amps and voltage regulators were tested on machines
whose performance I was responsible for.
https://en.wikipedia.org/wiki/Automatic_test_equipment

The second one matches other ammeters to 1 or 2 digits and I use
both
in series for discharge loads up to 10A. Together they each make up
for the deficiencies of the other. The 12V,12Ah battery is
discharging
on them at 0.5A.


Did I ever ask you why you didn't use a real battery for that? g
(real being 12v 35-275Ah) I set one up for use with the 45w HF trio
of panels and was able to power a 14" electric chainsaw with the 2kW
modified sine wave inverter, also from HF. It would have taken days
to recharge it (or more panels if needed for continued use.)


I do have "real" batteries that will run the fridge for about 20
hours. Once I'm satisfied with my discharge testing setup I'll get to
them. For now I'm testing and risking smaller, older, less valuable
jumpstarter and UPS AGMs. These tests are too long to watch and if the
low voltage disconnect fails the battery could be drained flat before
I notice.
-jsw




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