On Mon, 05 Oct 2009 22:31:54 -0700, Jeff Liebermann
wrote:

On Tue, 06 Oct 2009 11:33:22 +0800, who where wrote:

AN AGING MODEL FOR LITHIUM-ION CELLS
http://etd.ohiolink.edu/send-pdf.cgi/Hartmann%20Richard%20Lee%20II.pdf?acc_num=akron122 6887071
Warning: 278 page of a grad student's dissertation.
Skipping to Chapter VI - Conclusions, where it says:
A direct correlation was found between the cell capacity and
the open-circuit voltage of a fully discharged cell. Cell
resistance increased at a linear rate throughout the life
of the cells.

Without reading his/her dissertation, I'm not sure what (s)he's
measuring. What does (s)he define as a fully discharged cell, and how
does (s)he achieve that state?

See Pg 24 (section 2.2.2). He lists 3 methods along with their
limitations. I think (not sure) he's using coulomb counting
(amp-hrs). Section 2.2.3 follows with capacity measurement, which is
necessary to calculate the SOC. There's too much to quote. However,
you wanted the discharge point, and that's not covered directly. He
hints at:
For lead acid and lithium-ion batteries, the relationship
between the stabilized open circuit voltage, Eocs, and the
SOC is approximately linear (Wang & Stuart, 2002).
which implies that he uses 100% SOC as one point and extrapolates a
linear plot to zero SOC somewhere on the knee of the curve. However,
he also notes that it's temperature dependent, has hysteresis, and
requires substantial time to stabilize the terminal voltage. Unless I
missed something, he doesn't really specify how to measure the knee.

I won't pretend to understand all of it, especially since I'm buried
in work tonight and am having problems with (paying) distractions.
Maybe tomorrow.

I haven't really got the time to dig into the diss, but the expression
"A direct correlation was found between the cell capacity and
the open-circuit voltage of a fully discharged cell." doesn't make any
sense. If you define a fully discharged cell as one which has been
discharged to a pre-defined end-point (voltage), then all cells would
have the same EOD voltage except for rebound. Or is THAT what he is
getting at?

The circuit doesn't monitor individual cells.

The modules we used certainly did. There was a connection to each
series connection node. (And in assembly the connections had to be
made in the correct order.)

OK, I'm impressed(1). That's the way battery packs should be built
and monitored. However, why stop at monitoring individual cells?

It is more about safety than extracting maximum life/performance from
the packs. That's why these were termed "pack protection modules".
They provided:

(a) over-voltage cutoff
(b) excess charge current cutoff
(c) excess discharge current cutoff
(d) cell voltage imbalance cutoff
(e) undervoltage cutoff

clearly aimed at protecting the pack (and manufacturer) from hazardous
situations.

I prototyped NiCad and NiMH battery packs where each cell was also
charged individually. It's (fairly) well known that you can charge
these cells at almost any rate, as long as they're under 100% SOC. Go
over even slightly, and the cell gets very hot, very quickly. I've
built simulated chargers to do this and was able to charge NiCads
successfully at up to 20C (20 times rated capacity) to about 95% SOC.
Incidentally, the failures were rather impressive, including 2 small
fires, which might explain why such fast charging is not commercially
acceptable.

Because Ni-XX chemistries are current-mode charged, and actually
over-charged, that of itself provides a measure of SOC equalisation
which really makes it unnecessary to get involved in individual cell
charging in series strings. This was disucssed in a recent thread on
equalising SOC. Current-mode charging - series cell equalisation if
overcharged. Voltage mode (i.e. Li-XX) charging - parallel cell
equalisation.

I'm tempted to try the same tests with Li-Ion, but have
not been sufficiently inspired or bribed to do so.

Probably not worth the effort *if* the replication of charging
circuits adds much complexity.

(1) Note: I'm not easily impressed.

Jeff Liebermann wrote in
:

That only happens with FAT and FAT32. NTFS has a journaling
filesystem:
http://en.wikipedia.org/wiki/USN_Journal
which does not require a fsck if the user or battery protection
circuit suddenly pulls the plug.


However, an unscheduled shutdown during an update to the directory (or
other vital) sectors does seem to be one cause of 'file xxxx.xxx not
found' BSOD computers that are brought to me to fix.


--
bz 73 de N5BZ k

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

On Wed, 7 Oct 2009 19:08:06 +0000 (UTC), bz
wrote:

Jeff Liebermann wrote in
:

That only happens with FAT and FAT32. NTFS has a journaling
filesystem:
http://en.wikipedia.org/wiki/USN_Journal
which does not require a fsck if the user or battery protection
circuit suddenly pulls the plug.

However, an unscheduled shutdown during an update to the directory (or
other vital) sectors does seem to be one cause of 'file xxxx.xxx not
found' BSOD computers that are brought to me to fix.

I don't that very often, usually because I tend to do pre-emptive
replacements of hard disks (based on various criteria ranging from
S.M.A.R.T. reports to Ouigi board warnings). When I do see it, the
hard disk is usually ready to fail. Unfortunately, it tends to trash
files that Windoze like to scibble to constantly (i.e. the registry).

Also, some software that claims to speed up the machine turns on HD
write-caching. Bad idea.
http://www.pcmag.com/article2/0,2817,1819756,00.asp
Worse are PATA and SATA drives with a large (32MB) cache on the HD.
These do cache writes and will trash anything left un-flushed in the
cache if the power fails. Moral: the bigger they are, the harder
they crash.

Same with pulling the plug on USB, eSATA, and FireWire external
drives. Lots of ways to trash data, all of which apply equally to
FAT32. Despite these and other possible problems, NTFS journaling is
a major improvement over FAT32 and should be used whenever possible.

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

Jeff Liebermann wrote in
news
On Wed, 7 Oct 2009 19:08:06 +0000 (UTC), bz
wrote:

Jeff Liebermann wrote in
m:

That only happens with FAT and FAT32. NTFS has a journaling
filesystem:
http://en.wikipedia.org/wiki/USN_Journal
which does not require a fsck if the user or battery protection
circuit suddenly pulls the plug.

However, an unscheduled shutdown during an update to the directory (or
other vital) sectors does seem to be one cause of 'file xxxx.xxx not
found' BSOD computers that are brought to me to fix.

I don't that very often, usually because I tend to do pre-emptive
replacements of hard disks (based on various criteria ranging from
S.M.A.R.T. reports to Ouigi board warnings). When I do see it, the
hard disk is usually ready to fail. Unfortunately, it tends to trash
files that Windoze like to scibble to constantly (i.e. the registry).

disfortunately, the grad-student owned machines only get brought to my
attention when they are infested or crashed.
(one machine had over 50,000 virus infected files! "My machine is running
slow.")
Budget and personnel restraints prevent us from doing regular PM on most
state owned machines.
However, as part of my normal 'virus clean up' (often backup data,
reformat, reinstall OS is the fastest and safest method) I do check the
hard drives for signs of impending failure.

Also, some software that claims to speed up the machine turns on HD
write-caching. Bad idea.
http://www.pcmag.com/article2/0,2817,1819756,00.asp
Worse are PATA and SATA drives with a large (32MB) cache on the HD.
These do cache writes and will trash anything left un-flushed in the
cache if the power fails. Moral: the bigger they are, the harder
they crash.

Same with pulling the plug on USB, eSATA, and FireWire external
drives. Lots of ways to trash data, all of which apply equally to
FAT32. Despite these and other possible problems, NTFS journaling is
a major improvement over FAT32 and should be used whenever possible.

Agreed, although one of my cow-orker swears by the latest EFTn file system.





--
bz 73 de N5BZ k

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

On Fri, 9 Oct 2009 12:02:23 +0000 (UTC), bz
wrote:

disfortunately, the grad-student owned machines only get brought to my
attention when they are infested or crashed.
(one machine had over 50,000 virus infected files! "My machine is running
slow.")

The most I've seen is about 2,500 files. However, I rate my infected
machines by the number of different viruses, worms, and spyware types
found (not including cookies) that are actively running. No points
for counting infected emails that haven't run. So far, about 20
different types is the worst I've seen where the machine is still
sorta running.

Budget and personnel restraints prevent us from doing regular PM on most
state owned machines.
However, as part of my normal 'virus clean up' (often backup data,
reformat, reinstall OS is the fastest and safest method) I do check the
hard drives for signs of impending failure.

Well, I have a partial solution. Keep the user out of places they
shouldn't be playing.
http://www.microsoft.com/windows/products/winfamily/sharedaccess/default.mspx
It wasn't really designed for the purpose, but it's sufficient to
prevent total beginners, arrogant grad students, and ivory tower
professors, from trashing the operating system. Plenty of other
solutions, but this is the one I like. As soon as they shutdown, the
computer returns to its original state. Once a month, the PC goes
into the shop for an update, lube job, and oil change. I have it
installed at 2 car wash kiosks and one middle skool classroom. Other
than having to establish an update regime, it works well.

Actually, you don't really need to install MS Steady State on every
laptop in your system. Just one or two and the word will get around.
After that, merely the threat of having it installed should be
sufficient to inspire the students to clean up their act.

Also, you're being too nice. Make it clear that they are responsible
for their own data backups. If they bring a machine to you for
cleanup and disinfection, they should assume that it will be wiped and
reloaded from scratch.

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

Jeff Liebermann wrote in
:

On Fri, 9 Oct 2009 12:02:23 +0000 (UTC), bz
wrote:

....

Well, I have a partial solution. Keep the user out of places they
shouldn't be playing.
http://www.microsoft.com/windows/pro...access/default
.mspx

University policy and academic freedom....
My authority is rather limited when it comes to student owned computer or
computer under the authority of various professors. Also, many of the
computers I deal with are controling very expensive intruments.
The main problem in those cases is keeping them from putting such machines on
the internet.

It wasn't really designed for the purpose, but it's sufficient to
prevent total beginners, arrogant grad students, and ivory tower
professors, from trashing the operating system. Plenty of other
solutions, but this is the one I like. As soon as they shutdown, the
computer returns to its original state. Once a month, the PC goes
into the shop for an update, lube job, and oil change. I have it
installed at 2 car wash kiosks and one middle skool classroom. Other
than having to establish an update regime, it works well.

Would work well in a room with 50 similar computers. We don't have any
(though other departments do) such setups.

Actually, you don't really need to install MS Steady State on every
laptop in your system. Just one or two and the word will get around.
After that, merely the threat of having it installed should be
sufficient to inspire the students to clean up their act.

Also, you're being too nice. Make it clear that they are responsible
for their own data backups. If they bring a machine to you for
cleanup and disinfection, they should assume that it will be wiped and
reloaded from scratch.


When I am talking about someones years of research, I warn them to back up
everything, I ask if it is ok to wipe their drive if needed, I make an image
of the drive before I do anything to it, AND I restore all their data that
can be recovered!

I tell everyone about a guy I knew that had 9 years of research data in his
car (paper notes) and his car caught fire and burned. He never finished his
research and a few years later, he blew his brains out.

The lesson, I tell them, is
'make backups',
'make frequent backups',
'make multiple backups'
and 'keep your backups in a different place from where your computer is
located.'

It is bad enough to have to tell someone "I am sorry, I can't recover
anything from your [hard|thumb] drive.
There are companies that, for hundreds or thousands of dollars, will
disassemble it and attempt to recover your data. Is it THAT important to
you?"

I would much rather have someone say "thank you SO much for saving my data"
than "you ruined my life", or going 'postal'.




--
bz 73 de N5BZ k

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.