Today's Message Index:
----------------------
1. 04:52 AM - Re: Battery capacity test (bcone1381)
2. 05:33 AM - Re: Re: Battery capacity test (Werner Schneider)
3. 08:26 AM - Re: Re: Battery capacity test (Robert L. Nuckolls, III)
4. 09:24 AM - Re: Re: Battery capacity test (Alec Myers)
5. 10:26 AM - Re: Re: Battery capacity test (Robert L. Nuckolls, III)
6. 11:08 AM - Re: Re: Battery capacity test (Robert L. Nuckolls, III)
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| Subject: | Re: Battery capacity test |
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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| Subject: | Re: Battery capacity test |
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:
>
> 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
>
>
Message 3
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| Subject: | Re: Battery capacity test |
At 06:52 AM 2/15/2022, you wrote:
>
>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?"
Message 4
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| Subject: | Re: Battery capacity test |
Is there any way to measure charge acceptance efficiency, or =9Crechar
geability=9D, or is that not a criterion that degrades?
Specifically, for a battery whose capacity from =9Cfully charged
=9D to whatever discharge threshold is appropriate is x% of nominal, how man
y times that quantity of electrons needs to be provided to restore the maxim
um charge level it will hold.
On Feb 15, 2022, at 11:27, Robert L. Nuckolls, III <nuckolls.bob@aeroelectri
c.com> wrote:
=EF=BB At 06:52 AM 2/15/2022, you wrote:
>
> 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 w
atch?
>
> 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 m
aintain 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.j
pg
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_disc
harge_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_Discharg
e_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?"
Message 5
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| Subject: | Re: Battery capacity test |
At 11:23 AM 2/15/2022, you wrote:
>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?"
Message 6
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| Subject: | Re: Battery capacity test |
>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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