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nuckolls.bob(at)aeroelect Guest
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Posted: Mon Aug 24, 2020 12:46 pm Post subject: Some interesting observations |
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I've been gathering test data on some lithium products
in anticipation of doing an article on the quest for
an elegant integration of lithium cells into OBAM
light aircraft.
The two attached plots are interesting. The test article
is an EarthX ETX26D graciously donated to our 'cause' about
6 years ago. The plots illustrate battery behavior when
subjected to an array of charge/discharge profiles.
In the charge plots we see the battery response to
being charged in 0.5 volt steps over the range of 13.0
to 15.0 volts.
The 15.0 and 14.5 volt curves show a marked inflection
of charge current approx 2 hours after starting the
test. As the charge voltage is lowered, the inflections
(achievement of full charge) move outward in time and
are less pronounced. The interesting plot is at 13.0
volts . . no inflection . . . i.e. the battery doesn't
take on any charge.
The discharge plots are equally interesting. Note that
13.0v charge pumped no appreciable energy into the
battery chemistry. However, charging at 13.5 to 15.0
volts fully charges the battery. i.e. the battery
performance (except perhaps for charging time)
is unaffected by bus voltage. Note: the red plot
is what the battery delivered 'off the shelf' after
having been used/stored/maintained at intervals
over the past 5 or so years.
I not that the battery's demonstrated capacity is
on the order of 10.3 AH . . . down slightly from
demonstrated 11.6 AH when received as new.
These data are consistent with an article I
found on powerstream.com
https://tinyurl.com/yakthgt6
Where the author demonstrates the profound difference
in performance between Lithium Iron versus the
Lithium Polymer products. The article shows how the popular
and quite common Lithium Polymer cells fully charge at
4.2 volts with stored energy profoundly affected by
the top-off voltage. Same goes for Lithium Ion cells
widely offered as rechargeable power for a constellation
of consumer products.
Touchstone of note: No matter what claims are made
for the capacity of these cells, the real capability
of an 18650 Li-Ion cell is on the order of 2800 mAH. This
is easily confirmed by studies of published engineering data
sheets for name brand cells like Panasonic, A123,
Sanyo, etc.
https://tinyurl.com/y32rh8ym
Those ads on eBay touting 4000-10,000 mAH are blowing
smoke up your pant leg. Now, I not implying that
these cells are not serviceable products . . . price/
performance can be quite good but unless verified
by published performance data sheets, be skeptical
of stellar capacity claims.
That leaves us with the lowly Lithium Iron Phosphate
cell. It has the poorest capacity for unit volume of
all the popular products . . . but they are relatively
immune to catastrophic failure. Hence, the chemistry
of choice for the 'big guys' in TSO batteries for
CT aircraft. Typical energy ratings for the 18650
LiFePO4 are on the order of 1000-1500 mAH.
A noteworthy fallout of my studies suggests there
is no value in running the bus at any higher
than 14.0 volts for the LiFePO4 products.
Just thought I'd share some of the the bucket
of data point's I've gathered so far . . .
I'm still pondering the burned alternator
coils on the Revmaster engine . . . got some
ideas I want to massage on the test bench . . .
Bob . . .
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bob.verwey(at)gmail.com Guest
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Posted: Tue Aug 25, 2020 8:13 am Post subject: Some interesting observations |
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Bob I am often in awe of your energy in serving the OBAM community..thank you for your missives, they inspire neophytes like me to get "electron savvy"
Best Regards,Bob Verwey
082 331 2727
[img]https://docs.google.com/uc?export=download&id=0B5d7rgAInTuTUUZsUjY4QmJsdVU&revid=0B5d7rgAInTuTdDJDaXRFZVh3b3lMa3FWL0s3MFdzc01YRlNvPQ[/img]
On Mon, 24 Aug 2020 at 22:56, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:
Quote: | I've been gathering test data on some lithium products
in anticipation of doing an article on the quest for
an elegant integration of lithium cells into OBAM
light aircraft.
The two attached plots are interesting. The test article
is an EarthX ETX26D graciously donated to our 'cause' about
6 years ago. The plots illustrate battery behavior when
subjected to an array of charge/discharge profiles.
In the charge plots we see the battery response to
being charged in 0.5 volt steps over the range of 13.0
to 15.0 volts.
The 15.0 and 14.5 volt curves show a marked inflection
of charge current approx 2 hours after starting the
test. As the charge voltage is lowered, the inflections
(achievement of full charge) move outward in time and
are less pronounced. The interesting plot is at 13.0
volts . . no inflection . . . i.e. the battery doesn't
take on any charge.
The discharge plots are equally interesting. Note that
13.0v charge pumped no appreciable energy into the
battery chemistry. However, charging at 13.5 to 15.0
volts fully charges the battery. i.e. the battery
performance (except perhaps for charging time)
is unaffected by bus voltage. Note: the red plot
is what the battery delivered 'off the shelf' after
having been used/stored/maintained at intervals
over the past 5 or so years.
I not that the battery's demonstrated capacity is
on the order of 10.3 AH . . . down slightly from
demonstrated 11.6 AH when received as new.
These data are consistent with an article I
found on powerstream.com
https://tinyurl.com/yakthgt6
Where the author demonstrates the profound difference
in performance between Lithium Iron versus the
Lithium Polymer products. The article shows how the popular
and quite common Lithium Polymer cells fully charge at
4.2 volts with stored energy profoundly affected by
the top-off voltage. Same goes for Lithium Ion cells
widely offered as rechargeable power for a constellation
of consumer products.
Touchstone of note: No matter what claims are made
for the capacity of these cells, the real capability
of an 18650 Li-Ion cell is on the order of 2800 mAH. This
is easily confirmed by studies of published engineering data
sheets for name brand cells like Panasonic, A123,
Sanyo, etc.
https://tinyurl.com/y32rh8ym
Those ads on eBay touting 4000-10,000 mAH are blowing
smoke up your pant leg. Now, I not implying that
these cells are not serviceable products . . . price/
performance can be quite good but unless verified
by published performance data sheets, be skeptical
of stellar capacity claims.
That leaves us with the lowly Lithium Iron Phosphate
cell. It has the poorest capacity for unit volume of
all the popular products . . . but they are relatively
immune to catastrophic failure. Hence, the chemistry
of choice for the 'big guys' in TSO batteries for
CT aircraft. Typical energy ratings for the 18650
LiFePO4 are on the order of 1000-1500 mAH.
A noteworthy fallout of my studies suggests there
is no value in running the bus at any higher
than 14.0 volts for the LiFePO4 products.
Just thought I'd share some of the the bucket
of data point's I've gathered so far . . .
I'm still pondering the burned alternator
coils on the Revmaster engine . . . got some
ideas I want to massage on the test bench . . .
Bob . . . |
| - 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:
http://www.matronics.com/Navigator?AeroElectric-List |
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nuckolls.bob(at)aeroelect Guest
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Posted: Tue Aug 25, 2020 1:29 pm Post subject: Some interesting observations |
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At 11:06 AM 8/25/2020, you wrote:
Quote: | Bob I am often in awe of your energy in serving the OBAM community..thank you for your missives, they inspire neophytes like me to get "electron savvy"
Best Regards,
Bob Verwey
082 331 2727
|
To be inspiring is a teacher's prime
directive . . . thank you sir.
Bob . . .
| - 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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