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rv7a.n18pf(at)gmail.com
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 Posted: Sat Feb 12, 2022 4:35 pm Post subject: Battery capacity test |
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I built a battery capacity tester similar to the one described in this document:http://www.aeroelectric.com/articles/battest.pdf
I tested my battery down to 10.5 volts and got 152 minutes on a 16 AH battery. So I think I'm at ~62% of the original capacity.
Now my question - it was 17 degrees Fahrenheit (-8C) when I did my test, so do I need to compensate the test for temperature?
Either way I think it's time for a new battery. I'm just curious about the physics of the test when done at colder (or hotter!) than some standard temperature.
Paul Fisher
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Ceengland
Joined: 11 Oct 2020
Posts: 391
Location: MS
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| Posted: Sat Feb 12, 2022 8:02 pm Post subject: Battery capacity test |
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What was the duration when it was new?
Get BlueMail for Android
On Feb 12, 2022, at 6:39 PM, Paul Fisher <rv7a.n18pf(at)gmail.com (rv7a.n18pf(at)gmail.com)> wrote: | Quote: | I built a battery capacity tester similar to the one described in this document:http://www.aeroelectric.com/articles/battest.pdf
I tested my battery down to 10.5 volts and got 152 minutes on a 16 AH battery. So I think I'm at ~62% of the original capacity.
Now my question - it was 17 degrees Fahrenheit (-8C) when I did my test, so do I need to compensate the test for temperature?
Either way I think it's time for a new battery. I'm just curious about the physics of the test when done at colder (or hotter!) than some standard temperature.
Paul Fisher
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dj_theis
Joined: 28 Aug 2017
Posts: 56
Location: Minnesota
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| Posted: Sun Feb 13, 2022 6:18 am Post subject: Re: Battery capacity test |
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Good question Paul and I believe the short answer is “yes, temperature will affect battery performance.” It’s a common expectation that temperature will impact any chemical reaction rate and battery output is driven by the chemistry of the battery. The unknown is what the actual relationship (curve) is.
Here is one (unverified) note on battery performance vs. temperature.
https://www.intercel.eu/frequently-asked-questions/temperature-effects-on-batteries/
The actual performance reduction of your battery, as a function temperature, could be tested by simply repeating your test after warming the battery to room temperature (which might take a few hours to warm). Something that would be interesting to know, if you have time.
To Charlie’s point, the idea is to track your battery’s performance change as it ages. So, a single point of “time to 10.5 volts” has less value without knowing what it was when new (and probably at the same test temperature).
Dan
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Scratch building Sonex #1362
Still working on the Revmaster Alternator improvement |
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nuckolls.bob(at)aeroelect
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| Posted: Sun Feb 13, 2022 6:23 am Post subject: Battery capacity test |
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At 06:34 PM 2/12/2022, you wrote:
| Quote: | I built a battery capacity tester similar to the one described in this document:
http://www.aeroelectric.com/articles/battest.pdf
I tested my battery down to 10.5 volts and got 152 minutes on a 16 AH battery. So I think I'm at ~62% of the original capacity.
Now my question - it was 17 degrees Fahrenheit (-8C) when I did my test, so do I need to compensate the test for temperature?
Either way I think it's time for a new battery. I'm just curious about the physics of the test when done at colder (or hotter!) than some standard temperature.
Paul Fisher |
EXCELLENT question! Accurate evaluation of battery
condition, while not an art, is not a simple
matter of pulling out a dip-stick. As you have
observed, the temperature at which the test was
conducted represents a confounding influence
for comparing observed condition with as-new
condition.
I think I mentioned in the articles describing
this 'po boys capacity meter' as being only
loosely calibrated. However, if one holds
all potentially confounding effects constant,
then the meter does offer a reasonably accurate
COMPARISON of present condition with as-new
condition over a series preventative maintenance
tests.
The best use of this technique calls for testing
your battery when brand new . . . or certainly
within a short time after being placed in service.
Off the shelf batteries will GAIN a small capacity
after a few charge-discharge events. And by 'discharge'
we mean taken down by a significant fraction of
total capacity . . . say 1/3 or so.
Then use the value of the first test
as a benchmark for as-new capacity. Now you
have a number by which you can deduce percent
of remaining capacity with fair accuracy. Of
course, potentially confounding influences
need to be controlled. Do your test after
the battery has been on the bench at room temperature
and supported on a maintainer for 24 hours.
Of course a number with significant value represents
ENDURANCE. This number is easily deduced by
testing in the airplane where you use your
voltage sense device to control the e-bus
relay. Use ship's endurance loads to discharge
the battery. The time interval secured with
this test is a real performance number irrespective
of percent of as-new capacity.
Well . . . sort of. It's still a good thing
to be aware of the percentage of as-new capacity.
You are not well advised to make a replacement
at 60 or 70 percent of new even if that number
meets your endurance requirements. When a battery
has degraded that far, the slope representing
rate of decay is increasing rapidly.
Industry wide convention suggests 80% as a
practical and confident benchmark for replacement.
So that takes us back to bench testing in
controlled conditions with that micky-mouse
cap checker. It will flag the 80% condition
with satisfactory accuracy.
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
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nuckolls.bob(at)aeroelect
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| Posted: Sun Feb 13, 2022 6:24 am Post subject: Battery capacity test |
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At 10:01 PM 2/12/2022, you wrote:
| Quote: | | What was the duration when it was new? |
Right ON!
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
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rv7a.n18pf(at)gmail.com
Guest
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| Posted: Sun Feb 13, 2022 7:28 am Post subject: Battery capacity test |
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Thanks Bob. I thought this was a significant sentence "Do your test after the battery has been on the bench at room temperature and supported on a maintainer for 24 hours.". Just testing the battery on the plane in the non climate controlled hangar doesn't necessarily help.
Still learning.
Paul
On Sun, Feb 13, 2022, 08:27 Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:
| Quote: | At 06:34 PM 2/12/2022, you wrote:
| Quote: | I built a battery capacity tester similar to the one described in this document:
http://www.aeroelectric.com/articles/battest.pdf
I tested my battery down to 10.5 volts and got 152 minutes on a 16 AH battery. So I think I'm at ~62% of the original capacity.
Now my question - it was 17 degrees Fahrenheit (-8C) when I did my test, so do I need to compensate the test for temperature?
Either way I think it's time for a new battery. I'm just curious about the physics of the test when done at colder (or hotter!) than some standard temperature.
Paul Fisher |
EXCELLENT question! Accurate evaluation of battery
condition, while not an art, is not a simple
matter of pulling out a dip-stick. As you have
observed, the temperature at which the test was
conducted represents a confounding influence
for comparing observed condition with as-new
condition.
I think I mentioned in the articles describing
this 'po boys capacity meter' as being only
loosely calibrated. However, if one holds
all potentially confounding effects constant,
then the meter does offer a reasonably accurate
COMPARISON of present condition with as-new
condition over a series preventative maintenance
tests.
The best use of this technique calls for testing
your battery when brand new . . . or certainly
within a short time after being placed in service.
Off the shelf batteries will GAIN a small capacity
after a few charge-discharge events. And by 'discharge'
we mean taken down by a significant fraction of
total capacity . . . say 1/3 or so.
Then use the value of the first test
as a benchmark for as-new capacity. Now you
have a number by which you can deduce percent
of remaining capacity with fair accuracy. Of
course, potentially confounding influences
need to be controlled. Do your test after
the battery has been on the bench at room temperature
and supported on a maintainer for 24 hours.
Of course a number with significant value represents
ENDURANCE. This number is easily deduced by
testing in the airplane where you use your
voltage sense device to control the e-bus
relay. Use ship's endurance loads to discharge
the battery. The time interval secured with
this test is a real performance number irrespective
of percent of as-new capacity.
Well . . . sort of. It's still a good thing
to be aware of the percentage of as-new capacity.
You are not well advised to make a replacement
at 60 or 70 percent of new even if that number
meets your endurance requirements. When a battery
has degraded that far, the slope representing
rate of decay is increasing rapidly.
Industry wide convention suggests 80% as a
practical and confident benchmark for replacement.
So that takes us back to bench testing in
controlled conditions with that micky-mouse
cap checker. It will flag the 80% condition
with satisfactory accuracy.
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
|
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nuckolls.bob(at)aeroelect
Guest
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| Posted: Sun Feb 13, 2022 8:10 am Post subject: Battery capacity test |
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At 09:27 AM 2/13/2022, you wrote:
| Quote: | | Thanks Bob. I thought this was a significant sentence "Do your test after the battery has been on the bench at room temperature and supported on a maintainer for 24 hours.". Just testing the battery on the plane in the non climate controlled hangar doesn't necessarily help. |
It would IF you 'standardize' test
conditions for as-new and subsequent tests . . .
Here's one data point for capacity vs. temperature
in lead-acid chemistry.
https://tinyurl.com/ycng8hll
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
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Ceengland
Joined: 11 Oct 2020
Posts: 391
Location: MS
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| Posted: Sun Feb 13, 2022 8:54 am Post subject: Battery capacity test |
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On Sun, Feb 13, 2022 at 10:13 AM Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:
| Quote: | At 09:27 AM 2/13/2022, you wrote:
| Quote: | | Thanks Bob. I thought this was a significant sentence "Do your test after the battery has been on the bench at room temperature and supported on a maintainer for 24 hours.".  Just testing the battery on the plane in the non climate controlled hangar doesn't necessarily help. |
It would IF you 'standardize' test
conditions for as-new and subsequent tests . . .
Here's one data point for capacity vs. temperature
in lead-acid chemistry.
https://tinyurl.com/ycng8hll
Bob . . .
|
It would appear, based on that particular chart & converting 17F to -8C, his capacity is still close to 100%. Looks like pretty close to 62% at that temperature. (I realize that flooded cell charts might not perfectly translate to an AGM battery.)
Charlie
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Charlie |
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nuckolls.bob(at)aeroelect
Guest
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| Posted: Sun Feb 13, 2022 2:35 pm Post subject: Battery capacity test |
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| Quote: |
It would appear, based on that particular chart & converting 17F to -8C, his capacity is still close to 100%. Looks like pretty close to 62% at that temperature. (I realize that flooded cell charts might not perfectly translate to an AGM battery.) |
They are similar . . . I cannot disagree. I would
encourage a repeat test at room temperature.
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
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bcone1381
Joined: 25 Apr 2017
Posts: 42
Location: Southeast Michigan
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| Posted: Tue Feb 15, 2022 4:51 am Post subject: Re: Battery capacity test |
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Help me understand how the load test is performed. Lets say I have the HF 100 amp load tester. I charge my 12V 10 AH battery in my shop for 24 hours. Do I hook it up to the Load Tester and start my handy dandy little stop watch?
I think maybe I am watching the voltage and waiting for it to go down to a pre-determined level. I am guessing that Maybe my 10 AH battery ought to maintain a good voltage for 6 minutes on this 100A load tester.
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Brooks Cone
Bearhawk Patrol Kit Build |
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werner schneider
Joined: 24 May 2021
Posts: 58
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| Posted: Tue Feb 15, 2022 5:33 am Post subject: Battery capacity test |
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The instruction on the tester say, you load it for 10sec and check the
display on the correct scale for CCA for your battery and depending in
which scale area it is your battery is bad/weak or ok and it tells as
well about compensation if below 7 deg Celsius.
CCA is the value a battery can deliver for 30 sec when temperature is 0F
until voltage falls below 7.2 Volt
As an example the Odysee PC545 stats, CCA to be 185A, so you would at
0Fahrenheit have the capability for 30sec to load it with 185A until
voltage drops to 7.2V
On 15.02.2022 13:52, bcone1381 wrote:
| Quote: |
Help me understand how the load test is performed. Lets say I have the HF 100 amp load tester. I charge my 12V 10 AH battery in my shop for 24 hours. Do I hook it up to the Load Tester and start my handy dandy little stop watch?
I think maybe I am watching the voltage and waiting for it to go down to a pre-determined level. I am guessing that Maybe my 10 AH battery ought to maintain a good voltage for 6 minutes on this 100A load tester.
--------
Brooks Cone
Bearhawk Patrol Kit Build
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=506047#506047
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nuckolls.bob(at)aeroelect
Guest
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| Posted: Tue Feb 15, 2022 8:26 am Post subject: Battery capacity test |
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At 06:52 AM 2/15/2022, you wrote:
| Quote: | --> AeroElectric-List message posted by: "bcone1381" <bcone1964(at)gmail.com>
Help me understand how the load test is performed. Lets say I have the HF 100 amp load tester. I charge my 12V 10 AH battery in my shop for 24 hours. Do I hook it up to the Load Tester and start my handy dandy little stop watch?
I think maybe I am watching the voltage and waiting for it to go down to a pre-determined level. I am guessing that Maybe my 10 AH battery ought to maintain a good voltage for 6 minutes on this 100A load tester.
|
Good question. There are TWO qualities of battery
performance in which we have an interest.
(1) Capacity: a measure of ENERGY the battery will
deliver to critical loads in case of alternator
failure. I.e. ENDURANCE gaols.
(2) INTERNAL RESISTANCE: the ability to deliver
energy into a large LOAD, like a starter.
Those qualities are somewhat intertwined
but not tightly. An AGM battery may well
get your engine going while marginal for
meeting design goals for ENDURANCE.
Accurate quantification of those two qualities
is accomplished with two kinds of instrumentation:
(1) LOAD tester: a device capable of impressing
temporary loads many times greater than your
endurance loads while observing rate at which the
voltage falls.
(2) CAPACITY tester: a device that completely
drains the battery at some test-load that
is more in line design goals for ENDURANCE.
The devices we've been discussing in this thread
are LOAD testers. I've long and often suggested
acquisition of load testers like the Harbor
Freight devices:
http://aeroelectric.com/Pictures/Battery_Testers/HF_Variable_Load_Tester_1.jpg
and now . . .
http://aeroelectric.com/Pictures/Battery_Testers/HF_Fixed_Load_Tester.jpg
These devices are used to benchmark your battery's
internal resistance by placing a significant load
on the battery and observing ability to shoulder
that load after a period of time. With the
high current, variable tester we apply enough
load to reduce the battery voltage to 9 volts
(minimum output for cranking) for 15 seconds.
We ADJUST the load to maintain the 9 volt
reading. After 15 seconds, read the current.
(Follow instructions on the instrument for el-cheapo).
I've seen new, 18 a.h. svla products start
out at 600-700A and still be grunting 500A
after 15 seconds.
The el-cheapo load meter topic of this thread
cannot deliver so robust a load . . . but
TO BE SURE . . . if the battery tests 'weak'
at a piddling 100A presented by this device,
you can be quite sure that the battery is
toast.
A CAPACITY tester is a different breed of
critter. Here's one example of many:
http://aeroelectric.com/Pictures/Battery_Testers/CBA2_1.jpg
This is a computer driven device that lets you
load a battery to some constant current (say
equal to your endurance load?) and then count
the electrons as you suck them out.
http://aeroelectric.com/Pictures/Curves/Battery_Performance/300_vs_50mA_discharge_of_AA_cell.jpg
Here's a plot of data I gathered to demonstrate
the ability of a particular cell (in this case
some Maxell AA alkaline cells) to service
a range of loads. If we set 1.0 volts
as end-of-useful-life, then a 50 mA load
would be serviced TWICE as long compared to a
300 mA load. Clearly, INTERNAL resistance of these
small cells has a huge influence on the cell's
ability to perform at the heavier load. The
bottom axis of that plot is TOTAL electrons delivered.
6x the load tosses off about half of the cell's
potential energy.
Here's an exemplar plot of an LiFePO4 product.
http://aeroelectric.com/Pictures/Curves/Battery_Performance/LiFePO4_Discharge_Characteristics.jpg
Here we see that an 8x increase in load produces
an energy loss of only 11%.
Short Answer: Just starting your engine conducts
a practical 'load' test. If the cranking process
seems to be sagging, it's TIME to to a CAPACITY
test . . . but at some temperature near
your bench-mark value and AFTER a significant
service by a battery maintainer (topped off).
This el-cheapo load-tester is of good value
because for $dollars$ that wouldn't take
the family to McD's for lunch it does offer useful
information on battery condition. But it DOES NOT
take the place of measuring your battery's
ability to carry ENDURANCE loads as established
by your project design goals.
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
| | - The Matronics AeroElectric-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
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alec(at)alecmyers.com
Guest
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| Posted: Tue Feb 15, 2022 9:24 am Post subject: Battery capacity test |
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Is there any way to measure charge acceptance efficiency, or “rechargeability”, or is that not a criterion that degrades?
Specifically, for a battery whose capacity from “fully charged” to whatever discharge threshold is appropriate is x% of nominal, how many times that quantity of electrons needs to be provided to restore the maximum charge level it will hold.
On Feb 15, 2022, at 11:27, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com> wrote:
At 06:52 AM 2/15/2022, you wrote:
| Quote: | --> AeroElectric-List message posted by: "bcone1381" <bcone1964(at)gmail.com>
Help me understand how the load test is performed. Lets say I have the HF 100 amp load tester. I charge my 12V 10 AH battery in my shop for 24 hours. Do I hook it up to the Load Tester and start my handy dandy little stop watch?
I think maybe I am watching the voltage and waiting for it to go down to a pre-determined level. I am guessing that Maybe my 10 AH battery ought to maintain a good voltage for 6 minutes on this 100A load tester.
|
Good question. There are TWO qualities of battery
performance in which we have an interest.
(1) Capacity: a measure of ENERGY the battery will
deliver to critical loads in case of alternator
failure. I.e. ENDURANCE gaols.
(2) INTERNAL RESISTANCE: the ability to deliver
energy into a large LOAD, like a starter.
Those qualities are somewhat intertwined
but not tightly. An AGM battery may well
get your engine going while marginal for
meeting design goals for ENDURANCE.
Accurate quantification of those two qualities
is accomplished with two kinds of instrumentation:
(1) LOAD tester: a device capable of impressing
temporary loads many times greater than your
endurance loads while observing rate at which the
voltage falls.
(2) CAPACITY tester: a device that completely
drains the battery at some test-load that
is more in line design goals for ENDURANCE.
The devices we've been discussing in this thread
are LOAD testers. I've long and often suggested
acquisition of load testers like the Harbor
Freight devices:
http://aeroelectric.com/Pictures/Battery_Testers/HF_Variable_Load_Tester_1.jpg
and now . . .
http://aeroelectric.com/Pictures/Battery_Testers/HF_Fixed_Load_Tester.jpg
These devices are used to benchmark your battery's
internal resistance by placing a significant load
on the battery and observing ability to shoulder
that load after a period of time. With the
high current, variable tester we apply enough
load to reduce the battery voltage to 9 volts
(minimum output for cranking) for 15 seconds.
We ADJUST the load to maintain the 9 volt
reading. After 15 seconds, read the current.
(Follow instructions on the instrument for el-cheapo).
I've seen new, 18 a.h. svla products start
out at 600-700A and still be grunting 500A
after 15 seconds.
The el-cheapo load meter topic of this thread
cannot deliver so robust a load . . . but
TO BE SURE . . . if the battery tests 'weak'
at a piddling 100A presented by this device,
you can be quite sure that the battery is
toast.
A CAPACITY tester is a different breed of
critter. Here's one example of many:
http://aeroelectric.com/Pictures/Battery_Testers/CBA2_1.jpg
This is a computer driven device that lets you
load a battery to some constant current (say
equal to your endurance load?) and then count
the electrons as you suck them out.
http://aeroelectric.com/Pictures/Curves/Battery_Performance/300_vs_50mA_discharge_of_AA_cell.jpg
Here's a plot of data I gathered to demonstrate
the ability of a particular cell (in this case
some Maxell AA alkaline cells) to service
a range of loads. If we set 1.0 volts
as end-of-useful-life, then a 50 mA load
would be serviced TWICE as long compared to a
300 mA load. Clearly, INTERNAL resistance of these
small cells has a huge influence on the cell's
ability to perform at the heavier load. The
bottom axis of that plot is TOTAL electrons delivered.
6x the load tosses off about half of the cell's
potential energy.
Here's an exemplar plot of an LiFePO4 product.
http://aeroelectric.com/Pictures/Curves/Battery_Performance/LiFePO4_Discharge_Characteristics.jpg
Here we see that an 8x increase in load produces
an energy loss of only 11%.
Short Answer: Just starting your engine conducts
a practical 'load' test. If the cranking process
seems to be sagging, it's TIME to to a CAPACITY
test . . . but at some temperature near
your bench-mark value and AFTER a significant
service by a battery maintainer (topped off).
This el-cheapo load-tester is of good value
because for $dollars$ that wouldn't take
the family to McD's for lunch it does offer useful
information on battery condition. But it DOES NOT
take the place of measuring your battery's
ability to carry ENDURANCE loads as established
by your project design goals.
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
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nuckolls.bob(at)aeroelect
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| Posted: Tue Feb 15, 2022 10:26 am Post subject: Battery capacity test |
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At 11:23 AM 2/15/2022, you wrote:
| Quote: | | Is there any way to measure charge acceptance efficiency, or 'rechargeability', or is that not a criterion that degrades? |
Absolutely . . .
and yes, it is a consideration for battery designers
although seldom detailed in battery performance. This
it because the energy source used to charge the battery
is generally much more robust than the battery . . .
whether we can recharge it in say 10 hrs vs 12 hours
is not generally a big deal. Further, it's also not of
great concern if the energy you get out of the battery
is a fraction of total energy pushed into it .
But yes, I've conducted a number of tests on batteries
wherein total energy to top-off is compared to total
energy to end-of-life are compared. This is a measure
of the energy conversion efficiency. Numbers
on the order of 95% (for long, slow recharge/discharge
events and VERY low resistance) to perhaps 75% for hard,
rapid cycle.
The biggest single influence on energy loss is battery
internal resistance. Fast chargers for power tool
batteries will often produce a noticeable rise in
battery temperature as will hard discharges by
say, quickly drilling a lot of large holes.
But as the chemistry begins to wear out, internal
resistance goes up as does energy loss due to
internal heating. So conversion efficiency does
degrade along with ability to grunt a load or
keep the radio lit up.
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
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nuckolls.bob(at)aeroelect
Guest
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| Posted: Tue Feb 15, 2022 11:08 am Post subject: Battery capacity test |
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| Quote: | I am guessing that Maybe my 10 AH battery ought
to maintain a good voltage for 6 minutes
on this 100A load tester.
|
Unfortunately, there are features of the battery
and the load tester that would disprove your
supposition. Download this document:
http://aeroelectric.com/Mfgr_Data/Batteries/Enersys_Hawker/OdysseyPC545.pdf
Note the performance figures for various
loads.
It's a 14 AHour battery when-new if discharged
at 0.7 Amps for 20 Hours. (20 Hours x
0.7 Amps = 14 AHours)
But look what happens at about 7x that
load. (5.3 Amps x 2 Hours = 10.6 Ah)
What happened to 3.6 Ah of capacity?
It warmed the battery up. It's that pesky
internal resistance thing again.
Going to the top of the chart we see 128A
is good for about 2 minutes or only 4.3
Ah!
But if you were using your el-cheapo, HF
load tester to approximate this test, it
would probably terminate in smoke at less
than 2 minutes. That load tester is not
cooled well enough to dissipate that much
energy for so long.
For most of the lead-acid products
sold into vehicular and portable power
service, their AH energy can realized
only if discharged over 20 Hours; a
gentle rate that minimizes effects
of internal resistance and maximizes
availability of chemical energy contained
therein.
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
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nuckolls.bob(at)aeroelect
Guest
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| Posted: Fri Feb 18, 2022 5:34 am Post subject: Battery capacity test |
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Speaking of battery testing . . .
I've mentioned this battery information resource
many times over the years:
https://tinyurl.com/yckds5d9
This article in particular is germane to the
current thread:
https://tinyurl.com/ya6lm57f
Those who would care to deep-dive into battery
science and application are encourage to
exploit these offerings.
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
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nuckolls.bob(at)aeroelect
Guest
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| Posted: Fri Mar 18, 2022 8:26 am Post subject: Battery capacity test |
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At 07:26 AM 3/18/2022, you wrote:
| Quote: | --> AeroElectric-List message posted by: "Freedance" <PippaGibson6sQiY(at)yahoo.com>
The actual performance reduction of your battery, as a function temperature, could be tested by simply repeating your test after warming the battery to room temperature (which might take a few hours to warm). Something that would be interesting to know, if you have time.
|
Agreed. There are numerous confounding conditions that
affect measured capacity of a battery . . . including
calibration of the measuring system.
The capacity measurement techniques described in the
'Connection are COMPARATIVE studies that help an
owner/operator make qualified decisions for replacement
of the ship's battery.
This means that every measurement taken must be
conducted under the same conditions as subsequent
measurements. Have battery sitting at room temperature
for at least 24 hours with a maintainer attached.
Then measure endurance under an identical load
to compare against previous measurements. Contemporary
wisdom suggests replacement at 80% of as-new
capacity.
Having said that, I'm assuming that 80% of as-
new represents a battery that still meets your
design goals for battery-only endurance. This
speaks to a practice of sizing endurance loads
and battery size such that an as-new battery
EXCEEDS endurance requirements by 25% or more.
CAPACITY speaks to battery only endurance;
voltage at the end of a simulated cranking
event speaks to getting the fan running up
front. Two entirely separate considerations.
Important considerations since a modern
SLVA product incapable of running the electro-
whizzies for the required time might still
get the engine running.
Of the two qualities, CAPACITY is the
biggest, meanest bear in the woods.
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
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