Insert Tab A into Slot B
I've come across many a geeky problem, and taken some
chicken-scratch notes on how I solved 'em. So, here are some tutorials (I
use the term loosely) and quick fixes covering various topics.
Er..this section is new. Bare with me!
Chicken Scratch
Here's some bits and pieces I like to refer to on various topics.
Some I wrote, others were borrowed from sources around the net. Note
that the use of % in BSD or Linux code segments is meant
to resemble the command prompt - do not type it.
How to Dual Boot BSD with Windows, using the NT boot loader:
In BSD (Linux is similar, replace rwd0a with something like hda1), type:
% dd if=/dev/rwd0a of=bsd.pbr bs=512 count=1
Copy the .pbr file to your windows partition. In windows, add this to
c:\boot.ini:
c:\bsd.pbr="OpenBSD"
OpenBSD Package System
Ports are great, but packages are faster! Set a mirror for your
PKG_PATH, and use pkg_add with -v for verbose
output. You need to be root.
% PKG_PATH=ftp://mirrors.rcn.net/pub/OpenBSD/3.5/packages/i386/
% export PKG_PATH
% pkg_add -v perl
Even better, set PKG_PATH for all users by putting those top two lines
in /etc/profile. This works only with Bourne Shell
derivatives, such as ksh and bash (ymmv).
OpenBSD DHCPD Configuration
Modify /etc/dhcpd.conf. To hard-code an IP address for a specific MAC
address, use this:
host myputer {
hardware ethernet ab:01:cd:02:ef:03;
fixed-address 192.168.1.12; }
Run ps -ax | grep dhcpd to find the dhcp daemon. Kill it
and restart it with the same options noted by ps for changes to take
effect. A sig_HUP will not work.
BSD Disk Partitioning (disklabel) Notes
If you want to do your own custom disklabel, there are a few standard
things to keep in mind. First, each slice has its own name, designated
by a single character. The "a" partition is always where you mount root
(/). Next, the "b" partition is where your swap space goes. Swap is
typically made to be about 2 to 3 times the amount of physical RAM in
your system...but if you have 16MB or less, make this a minimum of 64MB!
After "a" and "b", things get a little odd. The "c" partition cannot be
used; it is a representation of the entire BSD partition in NetBSD and
FreeBSD, or the entire disk in OpenBSD. Similarly, "d" represents the
entire disk in NetBSD and FreeBSD, but is free for use in OpenBSD. Mount
points e through p are available in all BSD flavors.
Interesting information about charging NiMh and Li-Ion
batteries:
Charging circuits are not carefully designed for the impedance of a
particular batch of batteries. They are designed for the chemistry
involved (Ni-MH v. Li-Ion), for the approximate voltage (read, number of
cells), and for the really approximate capacity of the cells ( 1600,
1800, 2000 mah batteries would all be safely charged by the same
circuit, but a different circuit would be used for a 4000 mah battery
for example).
Li-Ion batteries are only slightly more difficult to charge than Ni-Mh
(you need four different charge states: Constant low-current for initial
charge, Constant high-current, Constant voltage, and Off, where Ni-MH
only needs two (Constant high-current and constant low-current)), and
have a few more safety precautions around them (For example, letting a
Ni-Mh pack discharge too far reduces it's capacity on subsequent
charge/discharge cycles; letting a Li-Ion pack discharge too far can
cause fire and noxious chemical release, in addition to a probable
permanent failure of the cell).
Thus, most of the arguments about matching cells to charging circuitry
are bogus.
However, it is correct that you must match the cells relatively closely.
This is not a problem when buying a bunch of cells a lot at a time, but
is extremely difficult when buying individual cells months or years
later to try and match to other cells in a pack. The physical reason for
matching is due to discharge - if one cell discharges before the others,
and the device does not detect it and shut down, the discharged cell
will be getting a "reverse charge". This reverse charging causes
irreversible chemical reactions at the cathode and anode, further
damaging the cell and reducing it's capacity.
His argument about the packs being ultrasonically welded is also valid,
but is more a technique/tools/workmanship issue than a roadblock. I do
not have the tools or techniques to seperate the halves of a battery
pack cleanly; that doesn't mean that a company devoted to doing so
couldn't develop them.
So, if the refurbisher replaces ALL cells in a pack with new ones, even
new ones with 20-30% more capacity, all the charging and protection
ciruitry will still work just fine, and the pack will be fine, subject
to the workmanship of the plastics work. If the refurbisher simply tests
to find the dead cells in a pack, and replaces only those, then the life
of the pack will be short as the new cells will NOT be matched to the
rest of the pack. It will appear to work fine, and even have good
capacity, for a number of charge/discharge cycles, but will fail long
before a pack built completely with new cells. If the refurbisher is a
real sleazeball, there are certain tricks one can use to rehabilitate
some NiCd and even NiMH packs that don't require disassembling the
packs, but have an even shorter expected lifetime (for example, using a
short duration, very high current pulse to vaporize internal crystals
that have poked through the seperator and are causing short-circuits).
So, the quality of the pack rebuild can be highly variable, and is based
on the rebuilder. Buying the cheapest rebuild you can find will probably
lead to heartache, as it may be "rebuilt" using one of the last two
approaches. Buying a more expensive one is no guarantee of a quality
rebuild, but it's more likely. I would only buy from an established
dealer who guarantees that ALL cells are replaced.
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